Tag Archives: geographic variation

Racism, science, and common sense

John Edward Terrell


Five ways to stop sounding like a racist if you aren’t one.

If you think racism isprejudice, discrimination, or antagonism directed against someone of a different race based on the belief that one’s own race is superior,” science has something surprising to tell you.


WHAT A DIFFERENCE A DECADE CAN MAKE. Back in 2006, Angela Davis remarked during a keynote address at the University of Wyoming honoring Martin Luther King Jr.’s birthday: “We have been basically persuaded that we should not talk about racism.”  Following the acquittal of George Zimmerman in the shooting death of African-American teen Trayvon Martin in 2013, the activist movement Black Lives Matter was born. Since then the issue of racism has been front and center in American politics. What remains elusive, however, is why racism however motivated finds such fertile ground in the human psyche.

The Earth is flat

Kyrie Irving, who plays basketball brilliantly for the Cleveland Cavaliers, made headlines in February 2017 for declaring boldly that the Earth is flat. He was perhaps pulling our collective leg.  His stated rationale, however, has more than a little bit of good old common sense to back it up:

“For what I’ve known for as many years and what I’ve come to believe, what I’ve been taught, is that the Earth is round,” he continued. “But if you really think about it from a landscape of the way we travel, the way we move, and the fact that—can you really think of us rotating around the sun and all planets aligned, rotating in specific dates, being perpendicular with what’s going on with these planets?”

Crazy thinking?  Maybe, but then what about this? A poll published two years ago by the U.S. National Science Foundation found that 26% of Americans don’t know that despite appearances to the contrary, the Sun does not go around the Earth.   Perhaps more astonishing, when asked, 52% of Americans evidently don’t agree with the statement that humans evolved from earlier animal species.

You don’t have to be Bill Nye or Neil deGrasse Tyson to see that all these instances of scientific ignorance make perfect sense from a common sense point of view despite being wrong. Furthermore, it wasn’t all that long ago most people on Earth in point of fact were misinformed in precisely these ways: yes, of course, the Earth is flat; yes, it is obvious that the Sun goes around the Earth; and haven’t you heard? Humans were created in their present form by a special act of Divine Will.

. . . and races are real

There are no polls I know of to back up the claim. Even so, it seems likely many people today—maybe even most—would also say they can’t possibly be at all racist because, don’t you know?, they don’t look down upon people in other races (see the dictionary definition reprinted above).

Editorial cartoon showing a Chinese man, surrounded by luggage labeled “Industry”, “Order”, “Sobriety”, and “Peace”, being excluded from entry to the “Golden Gate of Liberty”. The sign next to the iron door reads, “Notice—Communist, Nihilist, Socialist, Fenian & Hoodlum welcome. But no admittance to Chinamen.” At the bottom, the caption reads, “THE ONLY ONE BARRED OUT. Enlightened American Statesman—’We must draw the line somewhere, you know.'” 1882. Source: https://commons.wikimedia.org/wiki/File:The_only_one_barred_out_cph.3b48680.jpg. . . and races are real

This argument may be socially honorable, but if this is what many truly believe, then there are people who need to hear that just like the idea that the Earth is flat, so too, the notion that  human beings come in different kinds that can be labeled as “races” is just plain scientifically wrong.

As the anthropologist Jonathan Marks at the University of North Carolina – Charlotte and many others, too, have been saying for years, human genetic variation around the globe is real. But the same cannot be said for the commonsense claim that the Earth is peopled by separate and distinct human races.

As Marks has observed on numerous occasions, when we try to divide people up into different races, it’s not that we’re reading natural patterns of variation and simply extracting this idea from nature. Instead,

what we’re doing is we’re deciding that certain patterns of variation are less important than others, and certain patterns of variation are more important than others. We decide that the difference between a Norwegian and an Italian is not significant and so we’ll place them in the same category. And we decide that the difference between a Persian and a Somali is important; and so we’ll place them in different categories.

Sinner heal thyself

It is probably true that most human geneticists nowadays recognize that human beings don’t come in kinds—that is, races aren’t real. It is more than unfortunate, therefore, that geneticists today generally still don’t seem to know how to talk about human biological variation from place to place and down through time without using words—the term “population,” for example—that all too easily can mislead others less knowledgeable into believing science still endorses the old commonsense idea that human races exist in the real world to be embraced or savaged depending on one’s personal and moral proclivities.

No wonder, therefore, that dictionary definitions of racism (such as the one at the top of this commentary) can still make it sound like there is nothing wrong with the idea of race provided we don’t use this notion as an excuse for prejudice, discrimination, or antagonism.

The way forward

Most of us don’t believe the Earth is flat. Yet most of us live and act as if it were because this commonsense idea is a seemingly trivial lie that mostly works just fine in everyday life. Similarly, most of us may feel comfortable using the word race for the same reason. Truth be told, however, most of us also know the consequences of doing so can be deadly. Is there a way forward?

Here are 5 recommendations. They have been written specifically with geneticists in mind. But you don’t have to be a professional geneticist to add them to your own personal stock of “best practices.”

  1. Avoid whenever possible using facile concepts and terms such as ancestry, migration, and admixture when writing about human diversity.
  2. Abandon using the outdated concept of a “population,” and replace it with the statistician’s term “sample.”
  3. Stop writing about the “population structure” of this or that species, and instead report on their “genetic structure” as a species.
  4. Develop comparative databases documenting the genetic structure of other species to demonstrate publicly and repeatedly until the truth finally sinks in that geographic variation doesn’t have to be “racial” to be real.
  5. Create mathematical tools and network algorithms to use when mapping, analyzing, and reporting on the genetic structure of a species that unlike current methods (e.g., the popular computer program Structure) are non-categorical.

Racial migrations and human genetics: The “game changer” in the South Pacific that wasn’t – part 3

John Edward Terrell and Kevin M. Kelly


This is part 3 of a 3 part commentary


How many immigrants does it take to make a migration?

When presented with a sample comprising only 3+1 skulls, both scientific caution and parsimony suggest you should assume that colonists coming ashore back at the beginning of human history in Vanuatu and Tonga were probably more diverse, biologically speaking, than is witnessed by these four—at least until there is further evidence showing they did indeed come not just from a genetically homogeneous place of origin, but also a place where the inhabitants were as sui generis as they appear to be vis-à-vis others on earth (Skoglund et al. 2016: fig. 1b).

Logic such as this is well worth attending to. But in this instance, there is an equally logical way to get around the usual working assumption that people are likely to be more diverse than first appearances may suggest. Given how poorly specified are the two hypotheses under scrutiny here, it is anyone’s guess how big  we are supposed to think the boats must have been that brought early colonists to Vanuatu and Tonga around three thousand years ago. Even granting they may have arrived in more than one canoe, it would be reasonable to assume those arriving were fairly few in numbers. If so, then there is no need to assume blindly that those who came ashore in Vanuatu or Tonga constituted a representative (random) sample of the real human genetic diversity among those back home in the places where they came from, wherever on earth that was (Terrell 1986).

Furthermore, this is not all that might be reasonably assumed when trying to pin down the who, what, where, why, and when behind these four skulls. The number of pioneering colonists arriving  in canoes from elsewhere with them or before them may not only have been relatively few. They may also have been kin, i.e., biologically related to one another. If so, then possibly what makes these crania look sui generis in comparison with other people on earth, living and dead, may just be that we are seeing a “family resemblance” in these human remains (Terrell 1986; Walker and Hill 2014).

“Figure 1 New Guinea’s place in the southwestern Pacific (bathymetry downloaded from http://ingrid.ldeo.columbia.edu/SOURCES/ .WORLDBATH/.bath/based on the ETOPO5 5 · 5 min Navy data base).” Source: Terrell 2006: fig. 1
Homeward bound

For journalists and others, the real mystery of these remains, of course, is where these pioneers or their immediate forebears sailed from when they launched their boats to start a new life elsewhere. What is now known or can be reasonably assumed, therefore, about places to the west where they may have sailed from?

Until the Holocene stabilization of sea levels in the southwestern Pacific around 8,000–6,000 years ago, it is likely that much of the northern coastline of New Guinea was steep and uninviting of human settlement (as much of it still is today) except perhaps where favorable local circumstances may have at least temporarily trapped sediment in sandbars, coastal lagoons, and small river deltas. Little is currently known archaeologically about this coastline, which runs east-west for roughly 1,500 miles (2,400 km), and which would logically have been the most likely route between Asia and the farther reaches of the Pacific (Golitko et al. 2016). The best guess at the moment is that few people lived along this coast for the first 35,000–45,000 years of human history in the Pacific (Terrell 2006). In effect, earth and sea conspired to isolate New Guinea, like a sleeping giant, from frequent contact with islanders elsewhere both to the east in what is now popularly called Melanesia, and to the west in Island Southeast Asia (for biological support for this inference, see: Matisoo-Smith 2016: 391).

Following the Holocene stabilization of sea levels, however, coastal areas in Southeast Asia and the Pacific began to develop into rich floodplains, river deltas, and lagoons. By the mid Holocene, it is probable that people in the island realms to the east and west of New Guinea began to deal with one another back-and-forth more often as coastal people began to travel with greater reach along this immense island’s lengthy northern coastline (Torrence and Swadling 2008).

West meets East

Contrary to the notion that there are only two hypotheses about the prehistoric human settlement of the more remote islands in the Pacific east of New Guinea, there are numerous variants not only of those two old ideas but of others, too (for a recent review, see: Matisoo‐Smith 2016). Here we will introduce only one plausible reconstruction (Terrell, in press).

Initial baseline assumptions
  • Archaeologists now think people have been living in Southeast Asia for 50,000 years or so, and perhaps for not quite so long in the islands just east of New Guinea as far as Bougainville in the Northern Solomons.
  • The gradual flooding of the Sunda paleocontinent in what is now Southeast Asia since the Last Glacial Maximum ~21,000 years ago created extensive coastal environments that were ecologically rich and productive (Sathiamurthy and Voris 2006; Hanebuth et al. 2011: fig. 2). Similar extensive flooding did not occur in the area east of New Guinea labeled as Parkinson’s Islands (after the early ethnologist Richard Parkinson) on the map above (Lavery et al. 2016).
  • Due to this environmental advantage, it is probable that there were far more people living in Southeast Asia 6,000 years ago than there were in Parkinson’s Islands.
  • By the mid Holocene—contrary to the prevailing assumption in historical linguistics that doesn’t take this ecological advantage into consideration—it is probable that languages classifiable as Austronesian were widely spoken throughout Wallacea and elsewhere in Southeast Asia even as far north as Taiwan. But not yet in Parkinson’s Islands which had been isolated from Asia by the island of New Guinea.
  • Throughout the Late Pleistocene and early Holocene, Wallacea and Parkinson’s Islands were both areas of the Pacific where the advantages of travel by sea rather than by land nurtured the use of canoes and the development of local navigational methods and skills.
  • Canoes equipped with outriggers and sails were invented in Southeast Asia at some point in the Late Pleistocene or early Holocene. Simple dugout canoes remained the predominant boat type used for travel among coastal communities in Parkinson’s Islands.
Illustration taken from Labillardiere, (1800). Atlas pour servir a la relation du voyage de la recherche de la Perouse. Page Plate 43. Paris. Source: Labillardiere. (1800). Buka Island canoe (Solomon Islands) [digital image]. http://www.dspace.cam.ac.uk/handle/1810/239987 Modeling the relocation of immigrants from Wallacea
“The word proa comes from perahu, the word for “boat” in Malay.” Source: https://commons.wikimedia.org/wiki/File:Proa_(PSF).png
Modeling the relocation of immigrants from Wallacea
  1. A small Austronesian-speaking hamlet or village community left home for some particular local reason or reasons from somewhere in Wallacea—or possibly on the north coast of New Guinea—and made landfall in the Bismarck Archipelago.
  2. It is possible that wherever it was they came ashore, they arrived not as strangers but rather as old friends of some of the local people there in the Bismarcks (Terrell 2015).
  3. Among these immigrants were individuals skilled at pottery-making, and also skilled in the arts and rituals of building and sailing outrigger canoes with sails. Both of these technologies were new to the Bismarcks region. Moreover, such skills may not have arrived at the same time if travel back-and-forth between communities in Wallacea, northern New Guinea, and the Bismarcks became routine at least for awhile.
  4. The local people not only welcomed them, but often also acquired new ways of doing things—such as the art of pottery-making—from their immigrant neighbors, in some instances even their foreign language skills. The reverse may have also been true.
  5. Time passed, generations came and went. For now unknown reasons, it eventually became fashionable, prestigious, or perhaps even necessary for some people in the Bismarcks to set sail for islands yet farther to the south and east in the Pacific, although how many people in how many communities were involved, how often they sailed away, and for how many years this voyaging away from home in the Bismarcks went on are now all unknown and perhaps unknowable. 
  6. Even so, considering the passage of the time between (a) the first arrival of immigrants from the west and (b) the departure of some people generations later to settle down in other (more remote) places to the southeast, there is no reason to insist that these two separate episodes of human resettlement were similarly inspired or motivated (Walker and Hill 2014).
  7. Furthermore, given that both the voyaging technology and navigational skills required to colonize the more remote islands of the Pacific may have been available then only in some communities in the Bismarcks, it is not surprising that early settlers in Vanuatu, Tonga, and elsewhere had similar material culture traits (i.e., the so-called “Lapita cultural complex”).
Conclusions

Because the first immigrants who reached Vanuatu and Tonga were entering a vast and uninhabited part of the Pacific, it is probably not surprising that many nowadays have been seduced by the modern global distribution of Austronesian languages—from Madagascar to Rapa Nui (Easter Island) and from New Zealand to Taiwan—into thinking that such a vast geographic compass could only be the historical product of some kind of massive human migration that was singularly intentional and singularly premeditated from the very moment the first Austronesian-speaking immigrant stepped into the first canoe to sail from somewhere in island Southeast Asia  or on the north coast of New Guinea to the Bismarcks 3,000 and more years ago. It is wise to remember, therefore, that appearances can be deceiving.

Furthermore, today we know nothing about marriage (or sexual) practices in the Pacific in the prehistoric past. Although it is stating the case too simply, we do know that the basic building block of human genetic relatedness is the gene. Anyone who knows about the birds and the bees knows that genes can travel far and wide through sexual intercourse even if the people carrying them may only get as far away from home during their time on earth as the next village or two down the road. Consequently, there is no a priori reason to assume that race = language = culture. Or that genes necessarily traveled the Pacific millennia ago as the exclusive and enduring “property” of a massive and self-contained ethnic or ethnolinguistic migration that was able to keep its collective act together over thousands of miles and for hundreds, even thousands, of years. As some anthropologists like to say it, we need models of Pacific prehistory to work with that are “on the ground,” not “pie in the sky.”

Although we have been talking here almost exclusively about the Pacific Islands, the issue at stake is a global one. It is not just worrisome to find that even scientists may sometimes be unaware of the intellectual racism hidden in the conviction that the story of our species is a tale about ancestry, ancient migrations, and admixture. Commonsense ideas like these can be more than misleading. They can lend credence to other notions and old prejudices that can be harmful and sometimes deadly.  

Acknowledgments

We thank Ethan Cochrane, Mark Golitko, Tyrone Lavery, Lisa Matisoo-Smith, and Robin Torrence for assistance in the preparation of this 3-part commentary.

References

Bellwood, Peter. 2011. Holocene population history in the Pacific region as a model for worldwide food producer dispersals. Current Anthropology 52: S363–S378.

Gibbons, Ann. 1994. Genes point to a new identity for Pacific pioneers. Science 263: 32–33, p. 32.

Gibbons, Ann. 2001. The peopling of the Pacific. Science 291: 1735–1737.

Golitko, Mark, Ethan E. Cochrane, Esther M. Schechter, and Jason Kariwiga. 2016. Archaeological and Palaeoenviromental Investigations Near Aitape, Northern Papua New Guinea, 2014. Journal of Pacific Archaeology 7: 139–150.

Green, Roger C. 2003. The Lapita horizon and traditions – signature for one set of oceanic migrations. In C. Sand (ed.), Pacific Archaeology: Assessments and Prospects. Le Cahiers de l’Archéologie en Nouvelle-Calédonie 15. Nouméa: Service de Musées et du Patrimoine de Nouvelle-Calédonie, pp. 95-120.

Hanebuth, Till JJ, Harold K. Voris, Yusuke Yokoyama, Yoshiki Saito, and Jun’ichi Okuno. 2011. Formation and fate of sedimentary depocentres on Southeast Asia’s Sunda Shelf over the past sea-level cycle and biogeographic implications. Earth-Science Reviews 104: 92-110.

Lavery, Tyrone H., Andrew D. Olds, Jennifer M. Seddon, and Luke K‐P. Leung. 2016. The mammals of northern Melanesia: speciation, ecology, and biogeography.” Mammal Review 46: 60–76.

Matisoo-Smith, Elizabeth A. 2016. Human biology and population histories in the Pacific–Is there such thing as a Lapita people?. In: The Routledge Handbook of Bioarchaeology in Southeast Asia and the Pacific Islands, edited by M. Oxenham and H. Buckley, pp. 389–408. Routledge, London.

Sathiamurthy, E. V. H. K., and Harold K. Voris. 2006. Maps of Holocene sea level transgression and submerged lakes on the Sunda Shelf. The Natural History Journal of Chulalongkorn University, Supplement 2: 1-43.

Skoglund, Pontus, Cosimo Posth, Kendra Sirak, Matthew Spriggs, Frederique Valentin, Stuart Bedford, Geoffrey R. Clark, et al. 2016. Genomic insights into the peopling of the Southwest Pacific. Nature 538: 510–513.

Specht, Jim, Tim Denham, James Goff, and John Edward Terrell. 2014. Deconstructing the Lapita cultural complex in the Bismarck Archipelago. Journal of Archaeological Research 22: 89-140.

Specht, Jim, Chris Gosden, Carol Lentfer, Geraldine Jacobsen, Peter J. Matthews, and Sue Lindsay. 2016. A pre-Lapita structure at Apalo, Arawe Islands, Papua New Guinea. The Journal of Island and Coastal Archaeology: 1-22.

Terrell, John. 1986. Causal pathways and causal processes: Studying the evolutionary prehistory of human diversity in language, customs, and biology. Journal of Anthropological Archaeology 5: 187-198.

Terrell, John Edward. 2006. Human biogeography: Evidence of our place in nature. Journal of Biogeography 33: 2088-2098.

Terrell, John Edward. 2015. A Talent for Friendship. Oxford University Press.

Terrell, John Edward. In press. Understanding Lapita as history. In Oxford Handbook of Prehistoric Oceania, edited by Ethan Cochrane and Terry Hunt. Oxford University Press.

Terrell, John Edward, John Edward, Terry L. Hunt, and Chris Gosden. 1997. The dimensions of social life in the Pacific: Human diversity and the myth of the primitive isolate. Current Anthropology 38: 155–195.

Terrell, John Edward, Kevin M. Kelly, and Paul Rainbird. 2001. Foregone conclusions: In search of “Austronesians” and “Papuans.” Current Anthropology 42: 97–124.

Torrence, Robin, and Pamela Swadling. 2008. Social networks and the spread of Lapita. Antiquity 82: 600–616.

Walker, Robert S., and Kim R. Hill. 2014. Causes, consequences, and kin bias of human group fissions. Human Nature 25: 465-475.

© 2017 John Edward Terrell and Kevin M. Kelly. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES.

Racial migrations and human genetics: The “game changer” in the South Pacific that wasn’t – part 2

John Edward Terrell and Kevin M. Kelly


This is part 2 of a 3 part commentary


Necessary, plausible, and sufficient

Nobody, as far as we know, has come up with a universally accepted checklist of what makes a scientific hypothesis about anything something worth paying attention to. There are three criteria, however, that strike us as items that ought to be on such a checklist. Here is how we see these three applying to the conclusions now being made about the biological origins of the Polynesians.

Visualization by David Eccles of the two popularly assumed racial migrations from Asia out into the Pacific. Source: https://commons.wikimedia.org/wiki/File:Polynesian_Migration.svg
  1. Necessity: What needs to be explained? Both of the hypotheses weighed by the 31 contributors to the paper in Nature (Skoglund et al. 2016) under discussion here are alternative ways of trying to understand certain widely accepted observations about islanders in the Pacific: (a) people in Polynesia speak languages assigned by linguists to the Austronesian (Malayo-Polynesian) family, as do many people in Melanesia and Island Southeast Asia; (b) archaeologists now generally agree that what they have labeled the “Lapita cultural complex”* dating to ca 3300–2800 cal BP (Specht et al. 2016) exhibits a mix of cultural traits, some local to Melanesia and others apparently having roots to the west in Island Southeast Asia (Specht et al. 2014); and (c) the Lapita skulls found in Vanuatu and Tonga are morphologically and genetically sui generis (as the authors of this paper note, in some respects these four individuals are unique unto themselves).
  2. Plausibility: The two hypotheses considered by this consortium of scholars differ in their plausibility. (a) The idea that people traveled directly from Taiwan to Vanuatu and Tonga is basically impossible to assess given that nothing is said about how they might have done so—a striking omission considering the major dimensions of space and time involved. (b) The second hypothesis put on the table is similarly deficient, but it at least acknowledges that the set of material culture traits associated with the four Lapita skeletons in Vanuatu and Tonga wasn’t  imported in toto direct from Taiwan.
  3. Sufficiency: As Richard Levins observed years ago, truth is the intersection of independent lies. (a) Not only are the two hypotheses considered by this consortium of authors basically left unspecified, but (b) no reason is given for limiting the field of possible hypotheses solely to the two considered by these contributors.
The problem of equifinality

In light of #2 and #3 just noted, consider the old cliché “there is more than one way to skin a cat.” If you are a feline lover, there is even another way of saying more or less the same thing. As the biologist Ludwig von Bertalanffy made famous in the last century, you can call it equifinality. However phrased, it is wise to remember there is usually more than one way to get from A to Z, or even just A to B. The corollary relevant to the present discussion is that one cannot just assert that B came from A without offering a sufficient explanation for how that would have been possible. And more to the point, granting for the sake of discussion that B did somehow come from A, the scientific way of doing the job that needs to be done entails offering more than just 1–2 inadequately specified hypotheses.

The absence of evidence is not evidence of absence

According to these 31 authors: “our modelling indicates that Philippine populations (Kankanaey) are the closest outgroup to the First Remote Oceanians [i.e., these 4 skulls], indigenous Taiwanese (Atayal) second closest, and mainland southeast Asians such as the Dai most remote, consistent with models of population movement along a route from Taiwan to the Philippines to Near Oceania to Remote Oceania.” Maybe yes, maybe no.

Recall that only 14 of the 83 places in their modern comparative genetics sample are located in Island Southeast Asia, and none of the other 69 localities included in their analysis is in the region between the Philippines and northern New Guinea except for a single sample of 10 individuals from Sulawesi. Now look at a map of the region in question (see below).

“Figure 1 | Data from ancient and present-day populations. a, Locations of 778 present-day individuals genotyped on the Affymetrix Human Origins Array and 4 ancient individuals (red symbols).” Source: Skoglund et al. 2016: fig. 1a. Note: blue letters A and B added to the original.

Note two things, in particular. First, if it is true, as the song goes, that it’s a long, long way to Tipperary, then it is an even longer way from (A) Taiwan to (B) Tonga—more than 5,300 miles (8,500 km) in a straight line if a bee could fly that way that far. Second, notice the total lack of genetics samples from the big gap between the Philippines and the Bismarck Archipelago east of New Guinea (the few samples from New Guinea don’t count for reasons we will not go into here).

You don’t have to be a grumpy skeptic, therefore, to ask: if the four Lapita skulls from Vanuatu and Tonga look genetically most like people today in the Philippines, what about folks today, say, in the Moluccas and Halmahera off the Bird’s Head region of western New Guinea? And possibly also people living along  the north coast of New Guinea itself? Must we assume these four individuals from Vanuatu and Tonga somehow came all the way from Taiwan or the Philippines to come ashore there?[*]

Part 3: How many immigrants does it take to make a migration?


* The three skulls from Vanuatu were not found with the rest of their skeletons (Skoglund et al. 2016: supplementary notes). How they had been buried as well as their condition as skulls prior to burial suggest they had been cared for as portable heirlooms for an unknown period of time after death: “Ancient DNA was successfully obtained from three skulls from striking mortuary contexts: a jar burial containing a single skull (B17), an alignment of three skulls lying on the chest of a skeleton without a skull (B10B)”. There is a possibility that these individuals might have been long dead before their skulls arrived in Vanuatu. In contrast, with regard to the single individual from Tonga: “Ancient DNA was successfully obtained from the right petrous bone of burial SK10, a single primary interment of an adult female . . .”.


References

Bellwood, Peter. 2011. Holocene population history in the Pacific region as a model for worldwide food producer dispersals. Current Anthropology 52: S363–S378.

Gibbons, Ann. 1994. Genes point to a new identity for Pacific pioneers. Science 263: 32–33, p. 32.

Gibbons, Ann. 2001. The peopling of the Pacific. Science 291: 1735–1737.

Golitko, Mark, Ethan E. Cochrane, Esther M. Schechter, and Jason Kariwiga. 2016. Archaeological and Palaeoenviromental Investigations Near Aitape, Northern Papua New Guinea, 2014. Journal of Pacific Archaeology 7: 139–150.

Green, Roger C. 2003. The Lapita horizon and traditions – signature for one set of oceanic migrations. In C. Sand (ed.), Pacific Archaeology: Assessments and Prospects. Le Cahiers de l’Archéologie en Nouvelle-Calédonie 15. Nouméa: Service de Musées et du Patrimoine de Nouvelle-Calédonie, pp. 95-120.

Hanebuth, Till JJ, Harold K. Voris, Yusuke Yokoyama, Yoshiki Saito, and Jun’ichi Okuno. 2011. Formation and fate of sedimentary depocentres on Southeast Asia’s Sunda Shelf over the past sea-level cycle and biogeographic implications. Earth-Science Reviews 104: 92-110.

Lavery, Tyrone H., Andrew D. Olds, Jennifer M. Seddon, and Luke K‐P. Leung. 2016. The mammals of northern Melanesia: speciation, ecology, and biogeography.” Mammal Review 46: 60–76.

Matisoo-Smith, Elizabeth A. 2016. Human biology and population histories in the Pacific–Is there such thing as a Lapita people?. In: The Routledge Handbook of Bioarchaeology in Southeast Asia and the Pacific Islands, edited by M. Oxenham and H. Buckley, pp. 389–408. Routledge, London.

Sathiamurthy, E. V. H. K., and Harold K. Voris. 2006. Maps of Holocene sea level transgression and submerged lakes on the Sunda Shelf. The Natural History Journal of Chulalongkorn University, Supplement 2: 1-43.

Skoglund, Pontus, Cosimo Posth, Kendra Sirak, Matthew Spriggs, Frederique Valentin, Stuart Bedford, Geoffrey R. Clark, et al. 2016. Genomic insights into the peopling of the Southwest Pacific. Nature 538: 510–513.

Specht, Jim, Tim Denham, James Goff, and John Edward Terrell. 2014. Deconstructing the Lapita cultural complex in the Bismarck Archipelago. Journal of Archaeological Research 22: 89-140.

Specht, Jim, Chris Gosden, Carol Lentfer, Geraldine Jacobsen, Peter J. Matthews, and Sue Lindsay. 2016. A pre-Lapita structure at Apalo, Arawe Islands, Papua New Guinea. The Journal of Island and Coastal Archaeology: 1-22.

Terrell, John. 1986. Causal pathways and causal processes: Studying the evolutionary prehistory of human diversity in language, customs, and biology. Journal of Anthropological Archaeology 5: 187-198.

Terrell, John Edward. 2006. Human biogeography: Evidence of our place in nature. Journal of Biogeography 33: 2088-2098.

Terrell, John Edward. 2015. A Talent for Friendship. Oxford University Press.

Terrell, John Edward. In press. Understanding Lapita as history. In Oxford Handbook of Prehistoric Oceania, edited by Ethan Cochrane and Terry Hunt. Oxford University Press.

Terrell, John Edward, John Edward, Terry L. Hunt, and Chris Gosden. 1997. The dimensions of social life in the Pacific: Human diversity and the myth of the primitive isolate. Current Anthropology 38: 155–195.

Terrell, John Edward, Kevin M. Kelly, and Paul Rainbird. 2001. Foregone conclusions: In search of “Austronesians” and “Papuans.” Current Anthropology 42: 97–124.

Torrence, Robin, and Pamela Swadling. 2008. Social networks and the spread of Lapita. Antiquity 82: 600–616.

Walker, Robert S., and Kim R. Hill. 2014. Causes, consequences, and kin bias of human group fissions. Human Nature 25: 465-475.

© 2017 John Edward Terrell and Kevin M. Kelly. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES.

Racial migrations and human genetics: The “game changer” in the South Pacific that wasn’t – part 1

John Edward Terrell and Kevin M. Kelly


Here’s a hint about why scholars can be so captivated by what is basically an old-fashioned racial migration argument. They are apparently forgetting what they have been taught about the difference between a rhetorical argument and a scientific one.

The is part 1 of a 3 part commentary


THE IDEA THAT ONCE UPON A TIME the many islands of the South Pacific were colonized by different racial migrations out of Asia or the Americas (the latter a minority view) is as old as the hills. Or at any rate, at least as old as the earliest known encounters after 1492 between Europeans and the people living there.

1852 Bocage Map of Australia and Polynesia. The colored boundary lines show how this part of the world has long been subdivided into four cartographic regions labeled here as Malaisie (Malaysia), Micronesie (Micronesia), Polynesie (Polynesia), and Melanesie (Melanesia). Source: https://upload.wikimedia.org/wikipedia/commons/a/a2/1852_Bocage_Map_of_Australia_and_Polynesia_-_Geographicus_-_Oceanie-bocage-1852.jpg

The apparent remoteness and isolation of these islands and their inhabitants have long fueled the notion that here, if not necessarily elsewhere on earth, “race, language, and culture” all formerly tracked one another so closely that today, for instance, language differences can still be used successfully—and scientifically—not only to circumscribe and label separate “populations” in the Pacific (e.g., as different “ethnolinguistic groups,” ‘races,” and the like), but can also tell us how to reconstruct the prehistory and ancient migrations of separate and distinct “peoples” out into Oceania (Terrell et al. 1997).

It is generally considered impolite to say so, but the conventional word for this type of thinking is the word racism.

What seems astonishing is that racial thinking like this still frames how archaeologists, linguists, historians, social anthropologists, and human geneticists think about Pacific Islanders and write about their past. The most recent instance of this almost universal practice is possibly also the most revealing example of why otherwise informed scholars find themselves still under the spell of such an antiquated and unscientific idea.

Melanesians and Polynesians

As early as 1813 James Cowles Prichard was formally proposing—as others had earlier done more anecdotally—that the inhabitants of the Pacific Islands starting with New Guinea and neighboring places and moving on out eastward could be divided into “two principal classes.” In his own words (quoted in: Terrell et al. 2001):

The tribes which belong to the first of these are, strictly speaking, savages. They are universally in that rude unimproved state, which precedes all division of professions and employments. Consequently their political condition is that of perfect equality without any difference of ranks. Their physical character is of the rudest kind. Their form and complexion
approximate to those of the Negro.

Pritchard called these rude savages “the race of the Papuas.” Others would come to favor instead the term “Melanesians” (i.e., “black islanders”). He did not offer a name to use for the other—and supposedly superior—class of people except to say that such tribes were to be found in “the more distant regions of the Pacific Ocean.”

By 1843, his uncertainty about how to label the latter class of tribes had been resolved in favor of calling them “Malayo-Polynesians” since by then “a real kindred, or community of origin” had been established “by affinity of language” between islanders in Southeast Asia (i.e., “Malays”) and those in the more remote parts of Oceania, who were by then often labeled as Polynesians (i.e., “people of the many islands”).

Today the favorite label for the “affinity of language” noted by Pritchard and others in the 19th century between people in Polynesia and some of the inhabitants of Island Southeast Asia is the linguist’s label Austronesian.  Nowadays, too, those said to be in Pritchard’s so-called class of savages are generally called “Papuans,” although the label “Melanesians” is also still used by some.

Racial redux

Under the headline “‘Game-changing’ study suggests first Polynesians voyaged all the way from East Asia,” Ann Gibbons, a writer at Science magazine who had written previously about the origins of the Polynesians (Gibbons 1994, 2001), announced in surprisingly unqualified terms on 3 October 2016 that the identity of the first settlers of Polynesia was at last known, thanks to a paper then just published in Nature reporting on the first genome‑wide study of ancient DNA from  prehistoric Polynesians (Skoglund et al. 2016). Lo and behold, their ancestors were ancient East Asian mariners “who swept out into the Pacific. It wasn’t until much later that Melanesians, probably men, ventured out into Oceania and mixed with the Polynesians.”

To clinch the story, she then quotes experts who apparently ought to know what they are talking about.

“The paper is a game‑changer,” says Cristian Capelli, a population geneticist at the University of Oxford in the United Kingdom, noting that that it settles a decades‑long dispute. By showing that the East Asians hopscotched past islands already populated by Melanesians without picking up their genes, it is also a case study in how culture can initially bar mixing between groups. “Farmers move in and don’t mix much with the hunter‑ gatherers,” says evolutionary geneticist Mark Thomas of University College London. “We see this again and again and again” elsewhere in the world.

Not so fast

The late population geneticist and mathematical ecologist Richard Levins is famous in scientific circles for once having declared in no uncertain terms that “truth is the intersection of independent lies.’’  Given that what Gibbons, Capelli, and Thomas are saying is intellectually—if not necessarily politically—racist, why are they so confident? Particularly since the claim being endorsed is based on DNA extracted from only four skulls dating to around 3,000 or so years ago (three from Vanuatu, and one from the Tongan Islands) compared with the DNA of less than 800 present-day individuals from 83 places in Asia and Oceania.

To a cautious statistical mind, such figures ought to raise the worry that not enough is known about human genetic variation in this part of the world to warrant going far out on a limb by declaring resolutely that science has now told us not only where the ancestors of the Polynesians came from, but also how.

Add to this concern the additional information that all four of the women in the archaeological sample from the Pacific display their strongest apparent genetic ties with Taiwan—currently the most popular place to start the purported ancient migration to Polynesia—and with the Philippines.* Does a modern comparative DNA sampling of 778 individuals from 83 places in Asia and Oceania tell us enough about genetic similarities and differences throughout this immense region to overrule the reasonable doubt that linking the four prehistoric women with present-day people in Taiwan and the Philippines wasn’t exactly an unpredictable finding? Isn’t it reasonable to suspect this study might be biased, i.e., is an example of looking specifically for something—a genetic connection with Taiwan, in particular—where you most hope to find it?

Two alternative stories

The research report in Nature that Ann Gibbons wrote about in Science last October has 31 credited authors, a global mix of geneticists and archaeologists. Their report starts off with the assertion: “Pacific islanders today derive from a mixture of two highly divergent ancestral populations.” These authors then go on to tell us that there are two alternative stories—they call them hypotheses—about these two primal races (a word they do not use), and they say they now know which of the two to believe.

Both stories accept as true the unstated premise that biology, language, and culture co-vary closely with one another. The first story is an old tale still favored by some archaeologists (Bellwood 2011). If (a) race, language, and culture co-vary, and (b) Polynesians today speak languages of Southeast Asian origin (i.e., Austronesian, formerly called “Malayo-Polynesian”), then (c) it follows that the ancestors of the Polynesians came from Southeast Asia.  The second story is a more recent alternative reconstruction of Polynesian origins (Green 2003). If (a) race, language, and culture co-vary, and (b) the so-called “Lapita cultural complex” archaeologically associated with the first settlers of Polynesia is a cultural mix of Southeast Asian and Melanesian traits, then (c) the Polynesians racially must also be of similarly mixed biological origin.

Needless to say, these collaborators would not have written their report if they had found they couldn’t adjudicate the right choice between these two alternative stories. And they do not disappoint us: “Our study has shown that many of the first humans in Remote Oceania had little, if any, Papuan ancestry, in stark contrast [an odd choice of words?] to the situation today.” And if so, the second story evidently can’t be correct, right?

But this is not all they have to conclude. In their estimation: “Systematic study of ancient DNA from throughout Remote Oceania should make it possible to provide a detailed chronicle of the population movements and sex-biased population mixtures that shaped the ancestry of present-day Oceanians.”

Should we accept as true what they tell us? Is there a better way to think about what they report? In other words, what’s the chance they have been barking up the wrong stories altogether?

Part 2: Necessary, plausible, and sufficient


*  Only 14 of the 83 places in their comparative sample are located in Island Southeast Asia; 2 of these are on Taiwan and 6 in the Philippines. None of the other 69 localities is in the region between the Philippines and northern New Guinea except for a single sample of 10 individuals from Sulawesi. We return to these figures in Part 2 of this commentary.


References

Bellwood, Peter. 2011. Holocene population history in the Pacific region as a model for worldwide food producer dispersals. Current Anthropology 52: S363–S378.

Gibbons, Ann. 1994. Genes point to a new identity for Pacific pioneers. Science 263: 32–33, p. 32.

Gibbons, Ann. 2001. The peopling of the Pacific. Science 291: 1735–1737.

Golitko, Mark, Ethan E. Cochrane, Esther M. Schechter, and Jason Kariwiga. 2016. Archaeological and Palaeoenviromental Investigations Near Aitape, Northern Papua New Guinea, 2014. Journal of Pacific Archaeology 7: 139–150.

Green, Roger C. 2003. The Lapita horizon and traditions – signature for one set of oceanic migrations. In C. Sand (ed.), Pacific Archaeology: Assessments and Prospects. Le Cahiers de l’Archéologie en Nouvelle-Calédonie 15. Nouméa: Service de Musées et du Patrimoine de Nouvelle-Calédonie, pp. 95-120.

Hanebuth, Till JJ, Harold K. Voris, Yusuke Yokoyama, Yoshiki Saito, and Jun’ichi Okuno. 2011. Formation and fate of sedimentary depocentres on Southeast Asia’s Sunda Shelf over the past sea-level cycle and biogeographic implications. Earth-Science Reviews 104: 92-110.

Lavery, Tyrone H., Andrew D. Olds, Jennifer M. Seddon, and Luke K‐P. Leung. 2016. The mammals of northern Melanesia: speciation, ecology, and biogeography.” Mammal Review 46: 60–76.

Matisoo-Smith, Elizabeth A. 2016. Human biology and population histories in the Pacific–Is there such thing as a Lapita people?. In: The Routledge Handbook of Bioarchaeology in Southeast Asia and the Pacific Islands, edited by M. Oxenham and H. Buckley, pp. 389–408. Routledge, London.

Sathiamurthy, E. V. H. K., and Harold K. Voris. 2006. Maps of Holocene sea level transgression and submerged lakes on the Sunda Shelf. The Natural History Journal of Chulalongkorn University, Supplement 2: 1-43.

Skoglund, Pontus, Cosimo Posth, Kendra Sirak, Matthew Spriggs, Frederique Valentin, Stuart Bedford, Geoffrey R. Clark, et al. 2016. Genomic insights into the peopling of the Southwest Pacific. Nature 538: 510–513.

Specht, Jim, Tim Denham, James Goff, and John Edward Terrell. 2014. Deconstructing the Lapita cultural complex in the Bismarck Archipelago. Journal of Archaeological Research 22: 89-140.

Specht, Jim, Chris Gosden, Carol Lentfer, Geraldine Jacobsen, Peter J. Matthews, and Sue Lindsay. 2016. A pre-Lapita structure at Apalo, Arawe Islands, Papua New Guinea. The Journal of Island and Coastal Archaeology: 1-22.

Terrell, John. 1986. Causal pathways and causal processes: Studying the evolutionary prehistory of human diversity in language, customs, and biology. Journal of Anthropological Archaeology 5: 187-198.

Terrell, John Edward. 2006. Human biogeography: Evidence of our place in nature. Journal of Biogeography 33: 2088-2098.

Terrell, John Edward. 2015. A Talent for Friendship. Oxford University Press.

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Oxford Handbook of Prehistoric Oceania, edited by Ethan Cochrane and Terry Hunt. Oxford University Press.

Terrell, John Edward, John Edward, Terry L. Hunt, and Chris Gosden. 1997. The dimensions of social life in the Pacific: Human diversity and the myth of the primitive isolate. Current Anthropology 38: 155–195.

Terrell, John Edward, Kevin M. Kelly, and Paul Rainbird. 2001. Foregone conclusions: In search of “Austronesians” and “Papuans.” Current Anthropology 42: 97–124.

Torrence, Robin, and Pamela Swadling. 2008. Social networks and the spread of Lapita. Antiquity 82: 600–616.

Walker, Robert S., and Kim R. Hill. 2014. Causes, consequences, and kin bias of human group fissions. Human Nature 25: 465-475.

© 2017 John Edward Terrell and Kevin M. Kelly. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES.

Reconfiguring biological diversity 2. Coming to grips with diversity

John Edward Terrell


This is part 2 of a two part article

Coming to grips with diversity

Perhaps the greatest stumbling block to deciphering how biological diversity is patterned, or structured, in space and time within any given species is that most existing ways of modeling such diversity presuppose that genes are nested in some fashion within demonstrable and persistent primary units that can be labeled as populations, subpopulations, demes, communities, stocks, races, and like. Yet is this how biological reproduction works? Aren’t genes perfectly capable of “escaping,” so to speak, from such allegedly defining and confining “boxes” through the very acts of reproduction, reassortment, growth, and development?

It could be argued that there is irony in the fact that molecular genetics now has made it possible for scientists to map diversity at the genetic level. Yet many are still given to thinking about diversity as if they were compelled by the old limitations of their laboratory techniques to lump this new fine-grained evidence into inclusive nested sets (e.g., Pritchard et al. 2000; Greenbaum et al. 2016; Skoglund et al. 2016).

Perhaps it is not surprising, therefore, that some have concluded that “the observed pattern of global gene identity variation was produced by a combination of serial population fissions, bottlenecks and long-range migrations associated with the peopling of major geographic regions, and subsequent gene flow between local populations” (Hunley et al. 2009).

All three of these identified processes are plausible reasons for biological diversity in time and space. But aren’t all three of these population-level explanations ignoring individual agency and decision-making? Not to mention love, lust, and human compassion?

Moving beyond population modeling

Current population-level modeling based on molecular genetics is arguably an advance over older metapopulation models framing diversity as an ever-changing flux within species among discrete subpopulations inhabiting separate habitat patches linked by migration and extinction (Fig. 2). Certainly few today would accept that diversity within any species can be adequately explained solely or even largely as the product of fluctuating colonization and extinction events.

Figure 2. A simple metapopulation model at two time periods (A and B) attributing spatial diversity to a shifting dynamic of colonization and extinction events.

Similarly, the concept of the fitness landscape (also known as as an adaptive landscape; see Fig. 3) introduced by the geneticist Sewell Wright in 1932 is another long-debated way of modeling the dynamic interplay—or balance—of a number of plausible determinants of genetic variation in space and time. As Wright explained in 1932:

The most general conclusion is that evolution depends on a certain balance among its factors. There must be gene mutation, but an excessive rate gives an array of freaks, not evolution; there must be selection, but too severe a process destroys the field of variability, and thus the basis for further advance; prevalence of local inbreeding within a species has extremely important evolutionary consequences, but too close inbreeding leads merely to extinction. A certain amount of crossbreeding is favorable but not too much. In this dependence on balance the species is like a living organism. At all levels of organization life depends on the maintenance of a certain balance among its factors. (Wright 1932)

Figure 3. “Field of gene combinations occupied by a population within the general field
of possible combinations. Type of history under specified conditions indicated by relation
to initial field (heavy broken contour) and arrow.” Source: Wright 1932, fig. 4.

A “balance of factors” sounds right and reasonable, but are the ones he mentions the only major factors that must be taken into account? Surely adaptation is not the only driving force of evolution?

Agency and social networks

Consider the observation that human beings are notably variable in stature, weight, and other characteristics of their appearance. Clearly the gene mutations supporting such phenotypic variation have not resulted in what Wright would describe as “an array of freaks.” Evidently such diversity is not selected against—to use Wright’s way of framing the discussion. Why? Because much of the burden of human adaptation does not need to be genetically endowed. Instead, as most social scientists would insist, much of what we do supporting our survival and reproduction is accomplished using socially learned skills rather than by genetically inherited biological means.

Recently Greenbaum and his colleagues observed that the research strategies and tools of modern network analysis are increasingly being used to explore genetics questions in genomics, landscape genetics, migration-selection dynamics, and the study of the genetic structure of species more generally speaking (Greenbaum et al. 2016).

Adopting a networks approach to genetics makes it possible to come to grips not only with the ways in which racism—to return to Roseman’s point raised earlier—has shaped human variation in the past few hundred years, but also how our species’ mobility, adaptive skills, technologies, and social behaviors have been configuring human variation throughout the history of our species.

Figures 4 and 5 illustrate the potential value of using of network analysis in the study of genetic diversity. The first figure is a network mapping of localities reported in a genome scan published in 2008. While the patterning is complex, there is an obvious geographic signal in the genetic linkages shown. Figure 5 resolves the relationships among a smaller subset of the localities that had been sampled, specifically those in the Bismarck Archipelago-North Solomons region of the southwest Pacific.

Figure 4. Spring-embedding network mapping of the localities sampled in a genome scan of autosomal markers (687 microsatellites and 203 insertions/deletions) on 952 individuals from 41 Pacific populations). Mapping derived from the mean STRUCTURE assignment probabilities when K = 10 reported by Friedlaender at al. (2008) color-coded by geographic location. Blue-white = Asia; blue = Taiwan; black = Europe; red = Polynesia; pink = Micronesia; yellow = New Britain; purple = New Guinea; dark green = North Solomons; green = New Ireland; light green = New Hanover; pale green = Mussau. Source: adapted from Terrell 2010b, fig. 3.

 

Figure 5. Nearest-neighbor structuring of interaction among the localities sampled in the Bismarck Archipelago and North Solomons color-coded to show genetic clustering (blue nodes represent locations not represented in the genetic scan). Source: Terrell 2010b, fig. 11.Both network mappings suggest that geography has influenced the structuring of genetic similarities among people living in the sampled localities shown. Yet it also is apparent that the linkages shown may often be closer than geographic distance alone would lead us to expect. Judging by figure 5, the effect of isolation by distance is evidently constrained by social networks (as projected in this figure using nearest-neighbor linkages). Hence while geographic distance may be contributing to the patterning of genetic diversity among people in this part of the world, geography is by no means the whole story.
Conclusions

The network analysis briefly introduced in figures 4 and 5 had two principal aims, one phylogenetic, the other tokogenetic (Terrell 2010b). Do people living today in the Pacific segregate genetically along lines concordant with the reputedly separate (i.e., cladistic) histories of languages spoken there, principally the divide drawn by linguists and others between speakers of Austronesian and non-Austronesian (Papuan) languages (Terrell 2006)? To what extent does the genetic similarity among people living in different residential communities correlate with the nearest-neighbor propinquity of these sampled places?

Neither of these aims presuppose that the research goal is to define genetically discrete human populations (or subpopulations, demes, groups, communities, races, and the like) either a priori or by using, say, individual-based clustering (IBC) methods (e.g., Ball et al. 2010).

These two aims have more in common with those of the emerging field of landscape genetics (Dyer and Nason 2004; Garroway et al. 2008) than with most previous research in population genetics. However, both of these aims focus more directly on the genetic consequences of the behavior of organisms in space and time—in this case, humans—than on the geography, ecology, and environmental history of the locales where the people in question reside.

Both can also be seen as stepping back from Roseman’s observations about the impact of racial politics and social practices on the human genome in the past few centuries to underscore a more general issue in evolutionary biology: How much do the mobility and social behavior of individuals within any given animal species structure the genetic variation of that species?

As Dyer and Nason (2004) have remarked: “The evolution of population genetic structure is a dynamic process influenced by both historical and recurrent evolutionary processes.” Using network theory and visualization techniques to map the genetic structure of a species in space and time is still in its infancy. Reconfiguring how science grapples with the inherent complexity of evolution as an ever unfolding process using network approaches has the promise of making it easier to explore how comparable or dissimilar species are in their strategies for survival and reproduction (Fortuna et al. 2009).

Looking long and hard at what other species do to survive and reproduce may make it easier for us to see just how toxic our own social strategies—and the assumptions supporting them—can be.

Acknowledgements

I thank Neal Matherne and Tom Clark for their comments on a draft of this commentary.

References

Ball, Mark C., Laura Finnegan, Micheline Manseau, and Paul Wilson. 2010. Integrating multiple analytical approaches to spatially delineate and characterize genetic population structure: An application to boreal caribou (Rangifer tarandus caribou) in central Canada. Conservation Genetics 11, 6: 2131-2143.

Dyer, Rodney J., and John D. Nason. 2004. Population graphs: The graph theoretic shape of genetic structure. Molecular ecology 13, 7: 1713-1727.

Fortuna, Miguel A., Rafael G. Albaladejo, Laura Fernández, Abelardo Aparicio, and Jordi Bascompte. 2009. Networks of spatial genetic variation across species. Proceedings of the National Academy of Sciences 106, 45: 19044-19049.

Friedlaender, Jonathan S., Françoise R. Friedlaender, Jason A. Hodgson, Matthew Stoltz, George Koki, Gisele Horvat, Sergey Zhadanov, Theodore G. Schurr, and D. Andrew Merriwether. 2007. Melanesian mtDNA complexityPLoS One 2, 2: e248.

Friedlaender, Jonathan S., Françoise R. Friedlaender, Floyd A. Reed, Kenneth K. Kidd, Judith R. Kidd, Geoffrey K. Chambers, Rodney A. Lea et al. 2008. The genetic structure of Pacific IslandersPLoS Genet 4, 1: e19.

Garroway, Colin J., Jeff Bowman, Denis Carr, and Paul J. Wilson. 2008. Applications of graph theory to landscape genetics. Evolutionary Applications 1, 4: 620-630.

Greenbaum, Gili, Alan R. Templeton, and Shirli Bar-David. 2016. Inference and analysis of population structure using genetic data and network theory. Genetics 202.4: 1299-1312.

Hellenthal, Garrett, George BJ Busby, Gavin Band, James F. Wilson, Cristian Capelli, Daniel Falush, and Simon Myers. 2014. A genetic atlas of human admixture history.” Science 343, 6172: 747-751.

Hunley, Keith, Michael Dunn, Eva Lindström, Ger Reesink, Angela Terrill, Meghan E. Healy, George Koki, Françoise R. Friedlaender, and Jonathan S. Friedlaender. 2008. Genetic and linguistic coevolution in Northern Island MelanesiaPLoS Genet 4, no. 10 (2008): e1000239.

Hunley, Keith L., Meghan E. Healy, and Jeffrey C. Long. 2009. The global pattern of gene identity variation reveals a history of long‐range migrations, bottlenecks, and local mate exchange: Implications for biological race. American Journal of Physical Anthropology 139, 1: 35-46.

Kelly, Kevin M.,  2002. Population. In Hart, J. P. & Terrell, J. E. (eds.) Darwin and Archaeology: A handbook of key concepts, pp 243–256. Westport, Ct: Bergin & Garvey.

Moore, John H. 1994. Putting anthropology back together again: The ethnogenetic critique of cladistic theory. American Anthropologist (1994): 925-948.

Posada, David, and Keith A. Crandall. 2001. Intraspecific gene genealogies: Trees grafting into networks. Trends in Ecology & Evolution 16, 1: 37-45.

Pritchard, Jonathan K., Matthew Stephens, and Peter Donnelly. 2000. Inference of population structure using multilocus genotype data. Genetics 155, 2: 945-959.

Rieppel, Olivier. 2009. Hennig’s enkaptic system. Cladistics 25, 3: 311-317.

Roseman, Chartes C. 2014. Troublesome Reflection: Racism as the Blind Spot in the Scientific Critique of Race” Human biology 86, 3: 233-240.

Roseman, Charles C. 2014. “Random genetic drift, natural selection, and noise in human cranial evolution. Human Biology 86, 3: 233-240.

Skoglund, Pontus, Cosimo Posth, Kendra Sirak, Matthew Spriggs, Frederique Valentin, Stuart Bedford, Geoffrey R. Clark et al. 2016. Genomic insights into the peopling of the Southwest Pacific. Nature 538: 510-513.

Terrell, John Edward. 2006. Human biogeography: Evidence of our place in nature. Journal of Biogeography 33, 12: 2088-2098.

Terrell, John Edward. 2010a. Language and material culture on the Sepik coast of Papua New Guinea: Using social network analysis to simulate, graph, identify, and analyze social and cultural boundaries between communities. Journal of Island & Coastal Archaeology 5, 1: 3-32.

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Terrell, John Edward. 2015. A Talent for Friendship: Rediscovery of a Remarkable Trait. Oxford University Press.

Terrell, John Edward, and Pamela J. Stewart. 1996. The paradox of human population genetics at the end of the twentieth century. Reviews in Anthropology 25, 1: 13-33.

Wade, Nicholas. 2014. A Troublesome Inheritance: Genes, Race and Human History. Penguin.

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© 2017 John Edward Terrell. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES.

In the works: Mating, variation, and speciation: An interdisciplinary conversation

Source: https://commons.wikimedia.org/wiki/File:Limenitis_archippus_mating_2.jpg

While using network theory and visualization techniques to map the genetic structure of species in space and time is in its infancy, reconfiguring how science grapples with the inherent complexity of evolution as an ever unfolding process using network approaches has the promise of making it easier to explore how comparable or dissimilar species are in their strategies for survival and reproduction. Looking long and hard at what other species do to survive and reproduce may also make it easier for all of us to see just how toxic our own social strategies—and the assumptions supporting them—can be.

Reconfiguring biological diversity 1. Toxic and obsolete assumptions

John Edward Terrell


This is part 1 of a two part article

IN AN INSIGHTFUL REVIEW of Nicholas Wade’s recent book A Troublesome Inheritance: Genes, Race and Human History (Wade 2014), the anthropological geneticist Charles C. Roseman concluded that current scientific arguments against biological racism are weak and scattered. These failings—my word, not Roseman’s—are far more than just scientifically troubling. “To recuperate a useful scientific critique of race,” he argues, “we need to come to grips with ways in which the political processes of racism have shaped human organisms over the last few hundred years” (Roseman 2014).

As Roseman notes, nobody seriously contests that human variation “is structured in geographic space, through time, and across many social divisions.” What is still up for grabs is how to explain this observable diversity. And as Roseman emphasizes, how we explain human variation cannot ignore the divisive and often destructive power of racism as a potent driver of human evolution. “Without incorporating the effects of racism into models of human variation today, we will not be able to have a cohesive theory of genes and race, and the scientific critique of race will continue to have no teeth.”

While Roseman’s observations focus on human biological diversity, the weaknesses and uncertainties he has highlighted about our explanations for variation within our species apply also to modern science’s grasp of biological diversity more broadly speaking. From this more inclusive point of view, racism is just a particularly invidious human form of social behavior capable of patterning our genetic diversity in time and space. If so, what about other species? How does the patterning of their mobility and social behavior shape their genetic diversity?

“Populations,” “admixture,” and conventional wisdom

Although the human brain can be coaxed into paying close attention to detail and nuance,  as a thinking machine it generally favors expediency and the utility of knowledge over precision and accuracy.  It is not altogether surprising, therefore, that even scientists often still take it for granted that biological species are naturally subdivided into separate “populations” or “subspecies” that  may occasionally—say under changing demographic or environmental conditions—meet and mix, and thereby produce more or less isolated “admixed” new hybrids (e.g., Moore 1994; Hellenthal et al. 2014). The question being overlooked or at any rate downplayed is how real and persistent are these assumed “populations” (Terrell and Stewart 1996; Kelly 2002).

This question may sound academic, but it is not trivial, as Charles Roseman has underscored. When it comes to human beings, the favored word in scholarly circles may be the word population or perhaps deme, group, or community, but for the chap on the street, the more likely choice wouldn’t be one of these formal terms, but rather the more down-to-earth word race. (I still vividly remember being scolded by a famous biological anthropologist decades ago when I was an undergraduate for using this particular “r” word. “We don’t use that word anymore,” he told me. “We use the term stock  instead.”)

What’s at stake here

It has been a foregone assumption in most genetics research for years that different species are by definition and by their biology isolated reproductively from one another, i.e., individuals in different species cannot mate and give birth to viable offspring capable of sustaining life for longer than a single generation. However, even the most committed cladist accepts that biological relationships below the level of the species are tokogenetic, not phylogenetic (Posada and Crandall 2001; Rieppel 2009).

Figure 1. “Tokogeny versus phylogeny. (a) Processes occurring among sexual species (phylogenetic processes) are hierarchical. That is, an ancestral species gives rise to two descendant species. (b) Processes occurring within sexual species (tokogenetic processes) are nonhierarchical. That is, two parentals combine their genes to give rise to the offspring. (c) The split of two species defines a phylogenetic relationship among species (thick lines) but, at the same time, relationships among individuals within the ancestral species (species 1) and within the descendant species (species 2 and 3) are tokogenetic (arrows).” Source: Posada and Crandall 2001, fig. 1.

Here, therefore, is the conundrum. Call them what you want, populations within any given species are not inherently isolated reproductively either by definition and by their biology. Hence to treat populations as natural units, they must first be defined and demonstrated to be isolated and discernible as such in some other way, or ways. Can this be done?

Here is one favored way when the species in question is ourselves. Many people believe that the language you speak is a reliable sign or marker of your true ethnicity and even your race. Is this right?

Hardly. As both fable and risqué jokes alike would have it, any sailor arriving in a strange port of call is likely to discover soon enough that you don’t really need to speak the local language to enjoy a good time while ashore as long as you have a few coins in your pocket. Yet scholars have long written about people living in what some see as the “underdeveloped” regions of the world as being subdivided into recognizable ethnolinguistic groups, language communities, and the like despite the fact that such euphemisms for the old-fashioned word race pigeonhole rather than map the realities of their lives (Terrell 2010a).

But if neither biology nor language inherently—i.e., “naturally”—isolates and thereby subdivides human beings as a species into different populations, subpopulations, demes, communities, stocks, or races, is there anything that does? And what about other species on earth?

Competition and tribalism, or isolation-by-distance?

As Roseman has remarked: “All analyses of human variation make strong assumptions about the mode, tempo, and pattern whenever they interpret statistical results to make evolutionary conclusions” (Roseman 2016). Favored explanations for or against the assumption that our species can be subdivided into enduring natural populations largely fall into one or the other of two basic sorts.

On the one hand, there has long been anecdotal and scholarly evidence, too, that geography and topography can limit how well and how often people are able to stay in touch with one another socially and intellectually as well as sexually. As the authors of one recent study commented, research has shown that there is a strong positive correlation between global genetic diversity within our species and geographic distance. The correlations observed have often been interpreted “as being consistent with a model of isolation by distance in which there are no major geographic discontinuities in the pattern of neutral genetic variation” (Hunley et al. 2009).

As these same authors note, however, discordant gene frequency patterns are also common within our species. It is obvious, too, that physical and social impediments to gene flow have regularly produced both larger discontinuities as well as concordant allele frequency patterns than would be expected based solely on isolation-by-distance (clinal) models of variation (Ibid.).

Adding social impediments to the mix of possible explanations brings into play the second way many have tried to explain why people around the globe appear to be so diverse. While there are many variants of this alternative argument, the essential ingredients are the baseline assumptions that (a) competition between individuals and groups is the main driving force of evolution, (b) human beings are by nature selfish and aggressive creatures, and (c) until recently humans lived in small tribal groups that were not just suspicious of strangers and other communities near and far, but were frequently at war them them, too. All of these claims are not only questionable, but are arguably contrary to the fundamental evolved characteristics of our species (Terrell 2015).


Part 2: Coming to grips with diversity 


References

Ball, Mark C., Laura Finnegan, Micheline Manseau, and Paul Wilson. 2010. Integrating multiple analytical approaches to spatially delineate and characterize genetic population structure: An application to boreal caribou (Rangifer tarandus caribou) in central Canada. Conservation Genetics 11, 6: 2131-2143.

Dyer, Rodney J., and John D. Nason. 2004. Population graphs: The graph theoretic shape of genetic structure. Molecular ecology 13, 7: 1713-1727.

Fortuna, Miguel A., Rafael G. Albaladejo, Laura Fernández, Abelardo Aparicio, and Jordi Bascompte. 2009. Networks of spatial genetic variation across species. Proceedings of the National Academy of Sciences 106, 45: 19044-19049.

Friedlaender, Jonathan S., Françoise R. Friedlaender, Jason A. Hodgson, Matthew Stoltz, George Koki, Gisele Horvat, Sergey Zhadanov, Theodore G. Schurr, and D. Andrew Merriwether. 2007. Melanesian mtDNA complexityPLoS One 2, 2: e248.

Friedlaender, Jonathan S., Françoise R. Friedlaender, Floyd A. Reed, Kenneth K. Kidd, Judith R. Kidd, Geoffrey K. Chambers, Rodney A. Lea et al. 2008. The genetic structure of Pacific IslandersPLoS Genet 4, 1: e19.

Garroway, Colin J., Jeff Bowman, Denis Carr, and Paul J. Wilson. 2008. Applications of graph theory to landscape genetics. Evolutionary Applications 1, 4: 620-630.

Greenbaum, Gili, Alan R. Templeton, and Shirli Bar-David. 2016. Inference and analysis of population structure using genetic data and network theory. Genetics 202.4: 1299-1312.

Hellenthal, Garrett, George BJ Busby, Gavin Band, James F. Wilson, Cristian Capelli, Daniel Falush, and Simon Myers. 2014. A genetic atlas of human admixture history.” Science 343, 6172: 747-751.

Hunley, Keith, Michael Dunn, Eva Lindström, Ger Reesink, Angela Terrill, Meghan E. Healy, George Koki, Françoise R. Friedlaender, and Jonathan S. Friedlaender. 2008. Genetic and linguistic coevolution in Northern Island MelanesiaPLoS Genet 4, no. 10 (2008): e1000239.

Hunley, Keith L., Meghan E. Healy, and Jeffrey C. Long. 2009. The global pattern of gene identity variation reveals a history of long‐range migrations, bottlenecks, and local mate exchange: Implications for biological race. American Journal of Physical Anthropology 139, 1: 35-46.

Kelly, Kevin M.,  2002. Population. In Hart, J. P. & Terrell, J. E. (eds.) Darwin and Archaeology: A handbook of key concepts, pp 243–256. Westport, Ct: Bergin & Garvey.

Moore, John H. 1994. Putting anthropology back together again: The ethnogenetic critique of cladistic theory. American Anthropologist (1994): 925-948.

Posada, David, and Keith A. Crandall. 2001. Intraspecific gene genealogies: Trees grafting into networks. Trends in Ecology & Evolution 16, 1: 37-45.

Pritchard, Jonathan K., Matthew Stephens, and Peter Donnelly. 2000. Inference of population structure using multilocus genotype data. Genetics 155, 2: 945-959.

Rieppel, Olivier. 2009. Hennig’s enkaptic system. Cladistics 25, 3: 311-317.

Roseman, Chartes C. 2014. Troublesome Reflection: Racism as the Blind Spot in the Scientific Critique of Race” Human biology 86, 3: 233-240.

Roseman, Charles C. 2014. “Random genetic drift, natural selection, and noise in human cranial evolution. Human Biology 86, 3: 233-240.

Skoglund, Pontus, Cosimo Posth, Kendra Sirak, Matthew Spriggs, Frederique Valentin, Stuart Bedford, Geoffrey R. Clark et al. 2016. Genomic insights into the peopling of the Southwest Pacific. Nature 538: 510-513.

Terrell, John Edward. 2006. Human biogeography: Evidence of our place in nature. Journal of Biogeography 33, 12: 2088-2098.

Terrell, John Edward. 2010a. Language and material culture on the Sepik coast of Papua New Guinea: Using social network analysis to simulate, graph, identify, and analyze social and cultural boundaries between communities. Journal of Island & Coastal Archaeology 5, 1: 3-32.

Terrell, John Edward. 2010b. Social network analysis of the genetic structure of Pacific islanders. Annals of human genetics 74, 3: 211-232.

Terrell, John Edward. 2015. A Talent for Friendship: Rediscovery of a Remarkable Trait. Oxford University Press.

Terrell, John Edward, and Pamela J. Stewart. 1996. The paradox of human population genetics at the end of the twentieth century. Reviews in Anthropology 25, 1: 13-33.

Wade, Nicholas. 2014. A Troublesome Inheritance: Genes, Race and Human History. Penguin.

Wilson, David Sloan, and Edward O. Wilson. 2008. Evolution for the Good of the Group”: The process known as group selection was once accepted unthinkingly, then was widely discredited; it’s time for a more discriminating assessment. American Scientist 96, 5: 380-389.

Wright, Sewall. 1932. The roles of mutation, inbreeding, crossbreeding, and selection in evolution. Proceedings of the Sixth International Congress of Genetics , Vol. 1: 356-366.

© 2017 John Edward Terrell. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES.

Network science: The language of integrative research


Please note: this commentary, recovered on 9-Jan-2017, was originally published in Science Dialogues on 16-May-2015.


Mathematics, they say, is the language of science. When it comes to what is happening—or has happened—down here on earth, it is beginning to look like the right dialect of mathematics to learn is what is now being called (somewhat confusingly) network science.

When the goal is integrating research discoveries across disciplines as diverse as archaeology, primatology, neurobiology, and geochemistry, the mathematics of networks is the Esperanto of choice.

Field Museum in Chicago is one of the world’s largest natural history and anthropology museums. Scientists working there study the world and its human inhabitants from scores of different research directions, both pure and applied. Integrating these often seemingly disparate specialities so that the results of so much scholarship can be communicated to the public through exhibits and publications has always been a problem.

Under the leadership of Thorsten Lumbsch, Ph.D., the Director of Integrative Research at the Museum, “The Field” as it is affectionately known in Chicago is pushing back against research specialization using network science. Here is one example.

A social network is a set of actors defined by their ties, links, or relationships with one another (e.g., friendship networks, ecological networks, global trade networks, and protein interaction networks) rather than by their individual characteristics (attributes) as actors. Since the research focus is on relationships rather than on characteristics, statistical methods  in network science are being developed that do not need to assume—unlike in traditional statistical analyses—that the observations being studied are independent of one another.

Dr. Termeh Shafie, who is currently a Visiting Bass Scholar at the Field,  arrived in mid April from the Algorithimics Department at the University of Konstanz in Germany to help the Field’s scientists apply the statistical methods and models of network science to their research datasets which are as seemingly dissimilar as gorilla social interactions, sharks swimming in the ocean, the genetics of lichens, and the decorations on prehistoric American potshards.

When asked about her work at the Field Museum in Chicago, Termeh Shafie explains:

"The first step will be to learn more about the empirical data at hand, the hypotheses about these data being considered, and how to embed a network approach to them. The second step will be to develop network models based on these hypotheses. This requires the mathematical formulation of models, programming these models using statistical software, and then running simulations. Goodness-of-fit tests can be used to test the fit of the models to the data. Once suitable models are identified, statistics can be used to measure different properties of the networks under study and unlock information in them using the models as predictive tools. Within a level of certainty, we can then predict trends and behavior patterns even for parts of the networks we don’t yet have data for."

On Wednesday, May 13th, Dr. John P. Hart (Director, Research & Collections Division, New York State Museum), Dr. Mark Golitko (Regenstein Research Scientist), and James Zimmer-Dauphinee (2015 Regenstein Intern) participated with Shafie in a small-group Network Science Workshop at the Museum exploring ways to apply network analysis to a large database of information about pottery designs on ancient vessels from 102 archaeological sites to help unravel how communities across southern Ontario coalesced between ca. A.D. 1350 and 1650 into the larger regional populations that ultimately became the historically documented Huron confederacy.

Left to right: John Hart, Termeh Shafie, James Zimmer-Dauphine, Mark Golitko
Left to right: John Hart, Termeh Shafie, James Zimmer-Dauphinee, Mark Golitko

Shafie will be at the Field until August 15th, but even after she returns to Germany, she will continue to be the “networks link” between scientists at the Museum and the Algorithmics Unit under the direction of Professor Ulrik Brandes in the Department of Computer & Information Science at the University of Konstanz.

 

Migration, admixture, and human populations

Mark L. Golitko


Please note: this commentary, recovered on 8-Jan-2017, was originally published by Mark L. Golitko on Science Dialogues on 30-Jun-2015.


Cellarius_ptolemaic_system
The Ptolemaic universe as depicted by Johannes van Loon, ca. 1611–1686.

TWO NEW STUDIES IN EUROPEAN PREHISTORY have recently made headlines. The first (Haak et al. 2015) purports to show, using genetic data from ancient skeletons, that massive migration from the Central Asian Steppes into Europe during the Bronze Age likely introduced Indo-European languages, thus supporting the venerable “Kurgan” hypothesis championed by Marija Gimbutas decades ago. The second study (Smith et al. 2015) identified DNA from domesticated wheat (triticum) in submarine peat deposits off the southern coast of England dating to 8000 years ago, two millennia before such plants formed an identifiable component of crop assemblages in known terrestrial sites in England, and thus well ahead of the Neolithic agricultural “front.”

The validity of the later results remains to be seen—the DNA in question was cored out of the ocean bottom, and while the published results appear robust, it is unlikely that these data will single-handedly overturn the long-standing archaeological narrative of the Neolithic. That study does however provide a convenient point of digression for reexamining the first study and other similar studies of ancient genetics. Archaeologists have typically used two kinds of models to explain the past—diffusionist models in which ideas, things, and practices move, and migrationist models in which ideas, things, and practices move because people move. The movement of domesticated plants and animals of Near Eastern origins into Europe—the so-called “Neolithic Revolution”—has been the bell-weather case for testing these two types of explanations in archaeology. In the last three decades or so, human genetics has entered the picture as a way of testing competing hypotheses, first using modern DNA samples from living people in Europe and the Near East, and increasingly in the last decade, using ancient DNA (aDNA) extracted from archaeological burials (Pinhasi et al. 2012).

European population genetics, modern and ancient

Early studies of modern biological patterning (initially using blood types and other proteins) suggested a broad SE-NW trend in frequencies (Ammermann and Cavalli-Sforza 1984), one that was later confirmed when DNA sequencing became possible. This pattern was immediately interpreted as the outcome of a Neolithic period migration out of the Near East into Europe beginning after 8000 BC, swamping out “indigenous” European peoples (and their genes) that had been in place since at least the end of the last ice age (c. 12,000 years ago or longer). Vigorous debate ensued as some researchers argued that this trend could have resulted from a much earlier peopling of Europe by modern humans c. 45,000 years ago, or possibly during the reoccupation of Europe after the last glacial maximum (c. 22,000 years ago) by people who had occupied glacial refugia further south in Europe (see Pinhasi et al. 2012 and Deguilloux et al. 2012 for reviews of this work).

In 2005, the first study of DNA from actual early Neolithic skeletons was published (Haak et al. 2005), and the results were quite different from what most researchers had expected. As it turns out, early Neolithic skeletons, at least in central Europe (associated with an archaeological culture called the Linienbandkeramik or LBK) contain gene frequencies that are quite unlike those found in modern European populations. Specifically, mitochondrial DNA (mtDNA) haplogroups (sets of genomes related by shared mutations at particular locations on the genome suggesting common origins) thought to be clear markers of Neolithic population growth and movement were only present at relatively low frequencies, while one particular haplogroup—N1a—present at extremely low frequencies anywhere in modern day Eurasia and Africa, was quite common in the early Neolithic genepool. In the ensuing ten years, there has been a rapidly growing set of aDNA analyses performed in Europe, both on mtDNA (tracing descent through females) and Y-chromosome aDNA (tracing descent through males). As with modern DNA, measuring descent through males and females provides somewhat different answers, and suggests that on a whole, women have been more mobile than men in Europe (likely indicating a very old predominant pattern of patrilocality, e.g., Seielstad et al. 1998). In some places (parts of Northern Spain, for instance—see Sampietro et al. 2007), early Neolithic gene frequencies are not that different from earlier ones or modern ones, while in central Europe at least, the early Neolithic did witness a massive reshaping of the genetic landscape from a relatively genetically homogenous late-Paleolithic and Mesolithic background to a much more diverse Neolithic one, and little similarity is evident between the Neolithic and the present day (see Pinhasi et al. 2012 and Deguilloux et al. 2012 for reviews of this work).

The Haak et al. study (published earlier this month) identifies gene flow between central Asia and Europe in the Bronze Age, and a series of other recent studies also clearly demonstrate that the Neolithic is not the end of the story either. The researchers postulate a massive migration of Steppe populations into Europe associated with the Yamnaya archaeological culture, one that has been previously hypothesized to have spread Indo-European languages both eastwards and westwards out of Central Asia. aDNA research is for the most part slowly hammering the nail in the coffin of diffusionist models for the spread of agriculture, and for many, is now offering strong support for the spread of languages through massive migratory events (including Renfrew’s [1988] hypothesized spread of Indo-European during the early Neolithic).

Human “populations”

Care needs to be taken in interpreting these results, however. Population geneticists model the human past as a series of admixture events between discrete populations (see Hellenthal et al. 2014 for a recent attempt to define how many such populations there are). These populations may be defined in a number of ways—by geography (typically by continent), by language, by self-defined or externally perceived ethnicity, and in the case of palaeogenetics, by archaeological culture. There is thus an “LBK” or a “PPNB” set of gene frequencies which can admix or not (see for instance Fernández et al. 2015). This is a convenient shorthand, because it allows a small number of analyses (aDNA studies have sampled at most a few hundred individuals to date, while even modern studies are based on only thousands of individuals) to be taken as representative of some larger analytically meaningful population.

By Mike88n (Mike88n) [GPL (http://www.gnu.org/licenses/gpl.html)], via Wikimedia Commons (originally from Novembre et al. 2008).
Modern genetic map of Europe. (By Mike88n (Mike88n) [GPL (http://www.gnu.org/licenses/gpl.html)], via Wikimedia Commons (originally from Novembre et al. 2008)).

But what is a human population? That we have many ways of categorizing each other is unquestioned—we divide people up by race, income, clothing style, dialect, neighborhood, country, and a thousand other ways. It is also not implausible to imagine that real geographical boundaries such as major mountain chains, oceans, deserts, and so forth, may produce long-term vicariant barriers inhibiting interaction (i.e., people having sex with one another). That this is so is clearly demonstrated by the fact that modern gene frequencies are strongly patterned by geography in Europe, so much so that a multi-dimensional scaling plot (a way of representing many axes of variability on a single two-dimensional plot) of gene frequencies virtually recreates the geographic shape of Europe (Novembre et al. 2008). It is also everyone’s experience that humans live in social groups that can feel very real and rigid, and thus it might seem clear that human populations can be defined. However, the issue in palaeogenetics is different, namely, whether people live in sexual groups impermeable and long-lasting enough to explain the long-term configuration and development of gene frequencies, as well as serving as the basic scaffolding for other forms of human identity including the transmission of learning through time (i.e., culture and languages, including Indo-European ones).

Analytical simplification and historical reality

If the goal is simply to abstractly model how genes may have moved across the landscape historically, then perhaps an analytical fiction of discrete human “populations” is adequate for the job, similar to the use of the “gene” as analytical shorthand for modeling the complex network of DNA-RNA-protein interactions that drive biological function (e.g., Dawkins 2009). In econometrics, Friedman (1970) argued that it didn’t matter whether models were based on plausible assumptions, as long as those theories generated testable predictions that matched observations and resulted in predictive power. However, while predictive power may result even from a model with unrealistic starting assumptions, if social scientists want to explain what actually happened, our starting assumptions do matter. Their plausibility must be evaluated by examining how consistent they are with our knowledge of the world, updated in light of new information—if those assumptions are subsequently found wanting, we must reject the basic plausibility of our models, even if they produce outcomes consistent with empirical data (Nooteboom 1986). This is simply another way of stating that the same outcome can often be generated by several different models, and we need to turn to other lines of information to choose between them. In a recent paper, Pickrell and Reich (2014) use simulation to demonstrate that a number of opposing population genetic models used to explain human genetic patterning can produce the exact same results when operating over long periods of time.

As more aDNA analyses are published, the number of population migrations required to explain observed palaeo- and modern-gene frequencies in Europe (and by implication elsewhere) appears to be steadily increasing, in some cases seemingly at a rate of one per study (e.g., Hervella et al. 2015). This situation reminds me somewhat of the addition of spheres to the Ptolemaic system of planetary motions. Eventually, the Ptolemaic system grew so ponderous that some doubted it merely on the principal of parsimony. It took a radical rethinking of planetary positioning to generate a far simpler explanation of planetary motion. In the case of palaeogenetics (and other explanations of the past), perhaps a similar shift in thinking is required, one that moves away from the monolithic “billiard-ball” model of cultures and populations to something more plausible.

The human network

What should be the unit of analysis in historical genetics (and historical explanation more generally), and how do we create models that are consistent with other observations about human social structure and sexual behavior? In other words, how do we distinguish between competing historical genetic models by evaluating the basic plausibility of those models? One promising avenue comes from the recent explosion of interest in network analysis, which provides a robust method and body of knowledge for describing human social structure and comparing it to genetic patterning (e.g., Terrell 2010), and which does not necessarily require that one define broader units of analysis in advance, such as archaeological cultures. The challenge is to combine our knowledge of network structure in the human population (small-worlds and the like) with our understanding of genetics to create more plausible models of the human past. How this is to be accomplished in a formal mathematical sense remains to be seen.

This is more than just an academic concern—the popular media picks up on these studies and reinforces the viewpoint that humans do in fact come in particular “types” that can be identified through the new science of genetics—for instance, a recent distillation of one such aDNA study in a major media outlet described the results as indicating that modern Europeans derive from “three tribes” of ancient people, one of whom may be previously “unknown” to science (Rincon 2014). Do we really need “pulse-stasis” models for human population structure in the past? How do we adequately account for the fact that archaeological evidence suggests expansive social networks wherever and whenever we look, and that modern political/continental boundaries and perceived historical and cultural areas are not adequate units of analysis for splitting populations then or now? What happens if we resample our data and begin arbitrarily drawing lines that don’t correspond to these perceived political, geographical, linguistic, or archaeological categories? Does the story stay the same? A social networks perspective on the past is one way to transcend these problematic but common-sense ideas of human population(s) structure. If wheat can move beyond “Neolithic” communities thousands of years earlier than previously supposed, what else was moving?

References

Dawkins, R. (2009) The Selfish Gene. Oxford, Oxford University Press.

Deguilloux, M.-F., R. Leahy, M.-H. Pemonge, and S. Rottier (2012) European Neolithization and Ancient DNA: An Assessment. Evolutionary Anthropology 21: 24-37.

Fernández, E., A. Pérez-Pérez, C. Gamba, E. Prats, P. Cuesta, J. Anfruns, M. Molist, E. Arroyo-Pardo, and D. Turbón (2014). Ancient DNA Analysis of 8000 B.C. Near Eastern Farmers Supports an Early Neolithic Pioneer Maritime Colonization of Mainland Europe through Cyprus and the Aegean Islands. PLoS Genetics 10(6): e1004401. doi:10.1371/journal.pgen.104401.

Friedman, M (1970) “The Methodology of Positive Economics.” In Essays on Positive Economics. Chicago: The University of Chicago Press, pp 1-43.

Haak, W., P. Forster, B. Bramanti, S. Matsumura, G. Brandt, M. Tänzer, R. Villems, C. Renfrew, D. Gronnborn, K. Werner Alt, and W. Burger. 2005. Ancient DNA from the First European Farmers in 7500-Year-Old Neolithic Sites. Science 310: 1016-1018.

Haak, W., I. Lazaridis, N. Patterson, N. Rohland, S. Mallick, B. Llamas, G. Brandt, S. Nordenfelt, E. Harney, K. Stewardson, Q. Fu, A. Mittnik, E. Bánffy, C. Economou, M. Francken, S. Friederich, R. Garrido Pena, F. Hallgren, V. Khartanovich, A. Khokholov, M. Kunst, P. Kuznetsov, H. Meller, O. Mochalov, V. Moiseyev, N. Nicklisch, S.L. Pichler, R. Risch, M.A. Rojo Guerra, C. Roth, A. Szécsényi-Nagy, J. Wahl, M. Meyer, J. Krause, D. Brown, D. Anthony, A. Cooper, K. Werner Alt, and D. Reich (2015) Massive migration from the steppe is a source for Indo-European languages in Europe. Nature522: 207-211.

Hellenthal, G., G.B.J. Busb, G. Band, J.F. Wilson, C. Capelli, D. Falush, and S. Myers (2014). A Genetic Atlas of Human Admixture History. Science 343: 747-751.

Hervella, M., M. Rotea, N. Izagirre, M. Constantinescu, S. Alonso, M. Ioana, C. Lazăr, F. Ridiche, A.D. Soficaru, M.G. Netea, and C. de-la-Rua (2015). Ancient DNA from South-East Europe Reveals Different Events during Early and Middle Neolithic Influencing the European Genetic Heritage. PLoS ONE 10(6):e0128810. Doi:10.1371/journal.pone.0128810.

Nooteboom, B (1986) Plausibility in Economics. Economics and Philosophy 2: 197-224.

Novembre, J., T. Johnson, K. Bryc, Z. Kutalik, A.R. Boyko, A. Auton, A. Indap, K.S. King, S. Bergmann, M.R. Nelson, M. Stephans, and C.D. Bustamante (2008) Genes mirror geography within Europe. Nature 456: 98-103.

Pinhasi, R., M.G. Thomas, M. Hofreiter, M. Currat, and J. Burger (2012) The genetic history of Europeans. Trends in Genetics 28(10): 496-505.

Renfrew, C. (1988) Archaeology & Language: the Puzzle of Indo-European Origins. Cambridge, Cambridge University Press.

Rincon, P. (2014) Europeans drawn from three ancient ‘tribes’ BBC News Science and Environment, 9/17/2014.

Sampietro, M.L., O. Lao, D. Caramelli, M. Lari, R. Pou, M. Martí, J. Bertranpetit, and C. Lalueza-Fox (2007) Palaeogenetic evidence supports a dual model of Neolithic spreading into Europe. Proceedings of the Royal Society B 274: 2161-2167.

Seielstad, M.T., E. Minch, and L.L. Cavalli-Sforza (1998) Genetic evidence for a higher female migration rate in humans. Nature Genetics 20: 278-280.

Smith, O., G. Momber, R. Bates, P. Garwood, S. Fitch, M. Pallen, V. Gaffney, and F.G. Allaby (2015) Sedimentary DNA from a submerged site reveals wheat in the British Isles 8000 years ago. Science 347: 998-1001.

Terrell, J.E. (2010) Social Network Analysis of the Genetic Structure of Pacific Islanders. Annals of Human Genetics 74: 211-232.

© Mark L. Golitko. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES.

 

Human biogeography 3. Defining the agenda

John Edward Terrell


Please note: this commentary, recovered on 15-Jan-2017, was originally published in Science Dialogues on 12-Feb-2015.


Abstract – Human biogeography is not a thriving scientific enterprise. Why? In part because our species is remarkably talented at niche construction and highly inventive at adapting our socially learned ways of making a living and staying alive to meet the challenges and opportunities around us wherever we find ourselves on the planet. Nonetheless there is political as well as scientific need in the 21st century for an inclusive biogeographical perspective on human diversity recognizing that we are a globally distributed species whose diversity is framed by isolation-by-distance constrained by our social, economic, and political networks, and whose impact on the environment and our own sustainability is substantial and critically in need of informed restructuring.

This is part 3 of a 3 part series at SCIENCE DIALOGUES


POSSIBLY THE FIRST ATTEMPT IN RECENT YEARS to put humans on the agenda of biogeography was in 1974 at a small invitational conference in Washington, D.C. with this goal supported by the Wenner-Gren Foundation for Anthropological Research and organized by William Fitzhugh at the Smithsonian Institution and John Terrell at Field Museum of Natural History in Chicago (Kolata 1974). Human biogeography was provisionally defined by the organizers as “the study of the size, distribution, and population structure of, and the interactions among, human populations found in similar or divergent habitats, and of the conditions and events leading to the development and maintenance of similarities and differences among human populations living at various points on the earth’s surface” (Terrell 1977c: 5).

In 2012 the University of California Press published the first modern textbook in English on how and why we are distributed as we are globally, Alexander Harcourt’s Human biogeography (2012). As one reviewer noted about this book: “to study such patterns effectively one must not only work with an immense body of data, but also effectively employ theories and methods from both anthropology and biogeography” (Banks 2013: 39). Further, much of human diversity, as Harcourt emphasizes, is not about genes determining human behavior or even influencing what we do, but rather about our socially mediated interactions with the world (Hart 2012: 330).

Units of analysis

The biologist Richard Levins, one of the attendees at the Washington conference in 1974, pointed out that comparing the geographical distribution, variation, and demographic characteristics of human beings with these dimensions in other species is problematic. Biogeographers commonly then and now use taxonomic species as their units of analysis since (by definition, at least) species cannot interbreed. But what characteristics should be used to delimit appropriate human units for comparison given that all of us can at least potentially interbreed even if circumstance, preference, or spatial remove may keep Homo sapiens from being a panmictic species (Caspari 2003)?

When the science writer Gina Kolata reported in Science in 1974 on this conference, she noted that selecting the appropriate human units might be contingent on the research question being asked. If so, then defining the units might be done, for instance, by parsing linguistic, genetic, or cultural traits as the salient diagnostic characters (Kolata 1974). However, the crux of the issue raised by Levins and others at the conference remains. When it comes to variation within our species are the units however defined biologically meaningful? For example, are human groups defined linguistically (i.e., as ethnolinguistic populations) also biologically discernible, informative, and more than ephemeral (Kelly 2002)?

The answer is probably negative. The partitioning of people by language, for instance, is perhaps more extreme in the New Guinea region of the southwestern Pacific than anywhere else on earth. Although it has long been conventional to say that linguistic differences can be used to map biologically persistent populations, research on both cultural and genetic similarities and differences among communities in this part of the world has shown that their diversity when mapped geographically is structured most clearly not by language but rather by isolation-by-distance constrained by social networks and local environmental conditions such as ground slope and topographic ruggedness (Terrell 2010a, 2010b).

Systematic human biogeography

Although, as Barth remarked, it has long been conventional to talk about diversity within our species by presupposing there are discrete aggregations of people on earth that can be labeled as human populations, ethnic groups, and the like, it is probable that many of those attending the 1974 conference were fully aware of the challenges of defining units of analysis in the human sciences. They were not merely trying to map these sciences into the research agenda of species biogeography as then understood and practiced in the biological sciences. Yet it is also true, as John Terrell noted in the introduction to the resulting conference volume, that our human environment is not just a social construct: “People are [also] elements in a far more complex system, at best only partly of man’s design . . . within which a change in anyone element or relationship is likely to effect changes, of a greater or lesser degree, in all the others” (Terrell 1977a: 245).

Although the phrase has won few converts, Terrell suggested at the conference that such networks of interactions might be called geographic systems:

a geographic system is the interactive configuration among the size, distribution and interaction structure of a set of local populations and the elements and interaction structure of the area of their occurrence, analysed as a complex of intercommunicating variables within which a change in any one variable or relationship is likely to effect changes, of a greater or lesser degree, in all the others. (Terrell 1977b: 65)

Key here is the qualification “a greater or lesser degree.” As Herbert Simon once remarked: “To a Platonic mind, everything in the world is connected with everything else—and perhaps it is. Everything is connected, but some things are more connected than others” (Simon 1973: 23). What Simon had in mind were complex hierarchical systems: a broad class (physical, chemical, biological, social, or artificial) exhibiting what he termed “loose horizontal coupling” permitting “each subassembly to operate dynamically in independence of the detail of the others; only the inputs it requires and the outputs it produces are relevant for the larger aspects of system behavior” (1973: 16).

Networks human biogeography

Folk human biogeography presupposes that groups of some kind exist (perhaps simply because people say they exist), and similarities among such corporate players on the world stage of history can be attributed to common ancestry, adaptive convergence, or diffusion (which in the biological sciences is often called admixture) across the boundaries that supposedly exist between such corporate entities (Bashkow 2004). Systematic human biogeography interpreted the way Simon has described complex systems similarly also would appear to take for granted the presence of subsystems needing to communicate with one another but only in so far as inputs and outputs are relevant to the behavior and survival of the system as a whole. Yet harkening back to Levins’ concern in 1974: how should we define boundaries and systems in human biogeography?

Proximal-point analysis of the Solomon Islands and neighboring islands to the northwest (John Terrell, Smithsonian Conference, 1974).

Although not given much attention at the conference in 1974, an alternative strategy using graph theory was showcased during one of the presentations then (Terrell 1977c), and it is now widely recognized that Simon’s way of thinking about systemic relationships is not the only way to think about the dynamics of loosely-coupled systems. In 1973, for example, Mark Granovetter (1973) used graph theory—now more generally known as network analysis—to examine how the strength of our ties with others can determine our social mobility, the diffusion of ideas, the political and economic organization of society, and on a more general level, the cohesion of society writ large.

Network analysis enables us see the world around us as one of connections that shape observed phenomena, rather than as one where the intrinsic properties of predefined entities—groups, populations, tribes, systems, and the like—determine the behavior and outcomes of human interactions. Today network analysis in biogeography holds promise, but is still far from conventional (e.g., Kivelä et al. 2015; Radil et al. 2010; Terrell 2010b).

Conclusion

As Shakespeare asked, what’s in a name? It could be argued that anthropology, ethnology, or Erdkunde in the 19th century was simply another name for what would now be called biogeography focused narrowly on one species, namely us (Terrell 2006). This synonymy would be harder to assert for anthropology, human geography, and biogeography in the 20th century in part because the renowned anthropologist Franz Boas and his many prominent students in North America were generally successful at least within the academy at promoting the view that culture (i.e., social learning) is the cardinal trait uniquely defining us as a species (Lewis 2008)—although this historical claim can be contested (Koelsch 2003; Verdon 2006, 2007). What about the 21st century? Is there gain or advantage to be had today by still seeking to unite at least some of the elements of these realms of study under the neglected heading human biogeography?

Martinus Beijerinck in his laboratory, 12 May 1921. Source: http://commons.wikimedia.org/wiki/File:Mwb_in_lab.JPG. US.PD. “Beijerinck was a socially eccentric figure. He was verbally abusive to students, never married, and had few professional collaborations. He was also known for his ascetic lifestyle and his view of science and marriage being incompatible. His low popularity with his students periodically depressed him, as he very much loved spreading his enthusiasm for biology in the classroom.” http://en.wikipedia.org/wiki/Martinus_Beijerinck.

There is at least one practical reason to do so. While it might seem contentious, it could be said that science as a human activity is more tribal than our species itself. From a social scientist’s point of view—given that we do not naturally come in kinds—it seems astonishing that some geneticists today, for instance, would accept the old folk belief that human groups—geneticists call them populations—are so biologically isolated, and interactions, biological or otherwise, among people living in different places on earth are so rare, that it is proper to assume our biological similarities from place to place must be due to “sudden or gradual transfers of genetic material, creating admixed populations” (Hellenthal et al. 2014: 747; also Elhaik et al. 2014). Perhaps if there were a discipline called human biogeography, it would be more difficult for biologists to overlook what social scientists can tell them about our species, and vice versa.

Acknowledgments

I thank Eric Clark, Mark Golitko, John Hart, and Kevin Kelly for comments on the working draft.

References      § = suggested further reading

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© 2015 John Edward Terrell. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. The statements and opinions expressed are those of the author(s) and do not constitute official statements or positions of the Editors and others associated with SCIENCE DIALOGUES.