Category Archives: BIOLOGICAL

Coming soon: Racism, science, and common sense

John Edward Terrell


If you think racism is “prejudice, 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.

“In Self-Defense”. 1876 editorial cartoon by A. B. Frost. Depicts a caricatured former Confederates in the U.S. South with a knife and smoking gun in his hands standing over the corpse of an African-American toddler. Cartoon by A. B. Frost, published in “Harper’s Weekly”,
October 28, 1876, p. 880
Source: https://commons.wikimedia.org/wiki/File:InSelfDefense12w.jpg

More to come . . .

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

Coming soon: Tinker Tailor Soldier Ego, Part 1: Freud is dead

John Edward Terrell and Gabriel Stowe Terrell


THE FIRST THING WE NEED TO NOTE is that Freud is dead. No, we don’t mean the famous 20th century psychologist Sigmund Freud who died in 1939 at the beginning of World War II after struggling for years with cancer (Freud didn’t listen to his doctors, and he really, really liked to smoke cigars). We mean Freud’s way of thinking about how the brain works with the world popularly called Freudian psychoanalysis—although, yes, not every psychologist practicing today would agree with us that Freudian thinking is totally dead and buried.

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

The psychologist and Nobel Laureate Eric Kandel observed in an insightful overview published 1999 that this remarkable man revolutionized our understanding of the human mind during the first half of the 20th century. Unfortunately, as Kandel goes on to say, during the second half of the last century Freudian psychoanalysis did not evolve scientifically. It did not develop objective methods for testing Freud’s excitingly original ideas. As a consequence, Kandel gloomily concluded in his benchmark essay, psychoanalysis entered the 21st century with its influence in decline.

With the passing of psychoanalysis as an instructive way of thinking about how your mind works, nothing comparable in its scope and helpfulness has taken its place, leaving most of us today without a workable framework for understanding ourselves and why we do what we do. As Kandel concluded in 1999: “This decline is regrettable, since psychoanalysis still represents the most coherent and intellectually satisfying view of the mind.”

More to come . . .

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.

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.

Zambia paleo dig yields new insights on Permian-Triassic environments

Mark Alvey


Please note: this news story, recovered on 28-Jan-2017, was originally published in Science Dialogues on 27-August-2014.


Ken Angielczyk in the Luangwa Basin of Zambia holding two specimens of the dicynodont Diictodon. Photo by Roger Smith.

Associate Curator Ken Angielczyk of The Field Museum was part of an international team of collaborators that conducted paleontological fieldwork in Zambia between June 22 and July 31. Ken and his collaborators focused on Middle Permian (~265 Mya) to Middle Triassic (~240 Mya) rocks in two areas of the country, the Zambezi Basin in southern Zambia and the Luangwa Basin in northeastern Zambia. The team had done preliminary work in the Zambezi Basin in 2011 and 2012, but only spent a total of about 5 days working there. This time, they spent about two weeks there and their discoveries include multiple species of archaic amphibians and dinocephalians and dicynodonts (both ancient mammal relatives) from the Middle Permian, extremely well preserved fossil wood, and evidence that two temporally-distinct faunas are preserved in the Permian rocks in the Zambezi Basin. They also collected a large amount of geological data that will help complete the picture of the environments in which the plants and animals were living.

Ken’s colleagues Sebastien Steyer and Charles Beightol excavate a dinocephalian skeleton preserved in Permian rocks in the Zambezi Basin of Zambia. Photo: Cristian Sidor.

The team had conducted more extensive fieldwork in the Luangwa Basin in 2009 and 2011, and this year their work focused on rounding out their previous collections and collecting more geological data to understand  paleoenvironments. Among their discoveries is evidence of strong associations of particular dicynodonts with specific environments in the Late Permian rocks of the Luangwa Basin, and strong evidence of increased aridity and changes in the nature of river systems in the area moving from the Late Permian to the Middle Triassic. Ken and his collaborators will use these data to investigate the role environmental changes played in shaping the end-Permian mass extinction (the largest extinction in Earth history) and the recovery following the event.

Ulemosaurus svijagensis – primitive tapinocephalian from Middle Permian of Tatarstan. Illustration by Dmitry Bogdanov. Source: https://en.wikipedia.org/wiki/Ulemosaurus#/media/File:Ulemosaurus22DB.jpg.

And one important result of fieldwork like that: scientific publications.  Ken and colleagues have a paper in the July issue of Journal of Vertebrate Paleontology describing fossils of tapinocephalids from Southern Zambia.  Tapinocephalids are hippo-sized, herbivorous mammal relatives that lived about 265 million years ago; the fossils were discovered by Ken and his collaborators during short exploratory trips to the Zambezi Basin in southern Zambia in 2011 and 2012. They are the oldest known tetrapod remains from Zambia, and demonstrated the potential of the area for further paleontological exploration (as in previous item). This is also the second time that Ken and his teammates have discovered tapinocephalids in an area from which they were previously unknown (the first time was in 2008 in Tanzania).

© 2014 Mark Alvey. 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

Social network analysis: Hypothesis testing and what-if projections

John Edward Terrell


Please note: this commentary, recovered on 28-Jan-2017, was originally published in Science Dialogues on 13-June-2014.


GIVEN A RELIABLE DATABASE of information and a good computer program (such as Microsoft Excel), it is possible today to simulate a broad range of hypothetical real-world situations under differing possible opening and subsequent conditions (Embrechts and Hofet 2014). Said differently, by changing the parameters and values of a spreadsheet in meaningful ways it is possible to do informative what-if analyses of many kinds of situations—thereby gaining better understanding not only of possible but also plausible outcomes.

Similarly, it is possible to use a good network analysis program (such as UCINET; Borgatti et al. 2013) to simulate differing social situations and their plausible impacts. Here briefly described is one example based on research currently being done to explore the history of social networks along the north coast of Papua New Guinea.

Research question

During the last glacial maximum (~21,000 BP), sea-levels were ~125 m (410 ft) lower than they are today. It is likely that New Guinea’s northern coast was mostly a steep rocky shoreline offering few resources supporting human settlements (Chappell 1982).  As one consequence, New Guinea during the last Ice Age served more as a vicariant barrier than a land bridge between Asia and island Oceania (Terrell 2004).

Figure 1. New Guinea is the second largest island in the world. The northern coastline is over 1,600 miles (2,600 km) long. Shown here in comparison with the 48 mainland states in the U.S.A.

Both historical and archaeological evidence (Welsch and Terrell 1998; Terrell and Schechter 2011) suggests that villages on the northern coastline of New Guinea and the nearby offshore islands have been linked with one another by far-reaching social and economic networks for the past 2,000 years. An obvious and historically important question, therefore, is whether people and places there in the more distant past were similarly integrated in comparable widely-distributed communities of practice (Terrell n.d.).After the last Ice Age, however, sea levels rose steadily and then began to stabilize around their modern levels ~6,000–7,000 years ago. The resulting formation of coastal plains and environmentally productive lagoons and estuaries led to peak biodiversity (Hope and Haberle 2005) and probably also peak human population densities along this coastline between ~4000–2000 BP.

Materials and methods

Figure 2 shows two mini-max networks (Cochrane and Lipo 2010) drawn using UCINET 6 (version 6.289) and NetDraw (version 2.109) with the edges weighted at two different thresholds. The upper network shows the connectivity of places in this region given a maximal customary voyaging distance of 220 km or less—the greatest distance known to have been locally traversed during the Pleistocene and the mid-Holocene prior to ~3300 BP (Golitko and Terrell n.d.). The lower network has a threshold of 360 km—the greatest voyaging distance (from Makira-Ulawa in the Solomon Islands to Temotu in the Reefs/Santa Cruz group) documented as having been crossed during the first settlement of Remote Oceania ~3300–3100 BP (Irwin 1992).

Also shown in this figure are (a) the network positions (blue) of this region’s major sources of obsidian, a volcanic glass widely transported both historically and prehistorically in this region of the world; and (b) the location of our study area (red) on this coast in the Aitape district (Terrell and Schechter 2011).

Figure 2. Connectivity of obsidian sources (blue nodes) and Aitape (red node) on the Sepik coast of Papua New Guinea. Top: when the edge distance is 220 km or less; bottom: when it is 360 km or less (baseline image source: Mark L. Golitko). Likely cut lines in these networks projected using the Girvan-Newman algorithm (Girvan and Newman 2002) are shown here as heavy black lines. The same four groupings in the upper mapping occur at any assumed what-if linkage distance between 186 and 270 km.
Network analysis

Given these analyses, it is readily apparent that the what-if connectivity of these mappings differs markedly. Under the upper scenario, it can be hypothesized that obsidian from sources southeast of Aitape (they are on New Britain Island) has probably been transported from place to place at least as far west as Aitape, but it is less likely that obsidian from the other sources—located in the Admiralty Islands—has also arrived there despite the fact that these sources are geographically closer to our study area. The situation is different in the lower mapping. Instead of four probable groupings within the network shown, there are only two, and given this scenario, when obsidian has reached Aitape, it is more likely to have been mined at the nearer Admiralty sources.

Hypothesis testing

The presence of Admiralty Islands obsidian at prehistoric sites has not been securely documented archaeologically outside the Admiralty Group earlier than the mid 2nd millennium B.C. Its widespread popularity at Aitape and elsewhere in this part of the world thereafter is generally associated with suspected improvements in canoe-making design and technology thought to have been introduced from Island Southeast Asia around this same time (Specht et al. 2014; Terrell n.d.). However, it is also generally accepted that the movement of animals, obsidian, and people between islands and coastal villages was characteristic of life in this part of the world for many millennia before then—in other words, the suspected improvements in watercraft design and voyaging prowess did not initiate coastal and inter-island mobility in this region but instead made longer-distance travel more feasible and routine (Specht et al. 2014).

Figure 3. The actual geographic locations of the obsidian sources (blue dots) and the study area (red dot) at Aitape on the Sepik coast of Papua New Guinea.

While obsidian from Admiralty sources has been found at archaeological sites on the north coast of New Guinea that are younger than ~2000 BP, almost all of the obsidian that has been recovered archaeologically on mainland New Guinea older than ~3,500 BP has been sourced to the the Kutau/Bao locality on the Willaumez Peninsula of western New Britain (Summerhayes 2009).

Our fieldwork at Aitape in 1993/1994 and 1996 supported by the National Science Foundation ((BNS-8819618 and DBS-9120301)  discovered large quantities of obsidian and chert at localities along the former mid-Holocene shoreline (which at Aitape is now located several kilometers inland) including assemblages with notably high frequencies of  obsidian from New Britain marked by large average flake sizes (Golitko 2011)—an archaeological signature consistent with pre-2000 BP obsidian assemblages found elsewhere in northern Melanesia (Summerhayes 2009).

Therefore, given our two what-if network analyses and this archaeological evidence it may be hypothesized that obsidian has probably been indirectly available to people living in what is now the Aitape district ever since the stabilization of world sea levels around 6,000–7,000 years ago, but it is likely that the major sources of this natural glass prior to ~3,500 BP were those located on New Britain.

With funding from the National Science Foundation my colleague Dr. Mark Golitko is currently (June–July 2014) leading a research team at Aitape that is surveying archaeological sites there on the mid-Holocene (~5000 BP) shoreline (as reconstructed from estimated local uplift rates and sea-level records) to document how far-reaching or alternatively how restricted were cultural and material exchanges on this coast at that time. Discovering how isolated or widely linked communities at Aitape were during the mid-Holocene is  critical to understanding the patterning of modern human diversity in northern New Guinea and elsewhere in the Pacific (Terrell 2010a, 2010b).

Conclusions

Obsidian has long been a popular although largely nonessential raw material in the Pacific (as elsewhere on earth) despite the fact that alternative and equally useful cutting materials (such as bamboo) are readily available. Hence the ancient transport of obsidian through inter-community networks is commonly interpreted by archaeologists as more a social phenomenon than a practical (“economic”) necessity (Torrence 2011). As suggested by the what-if analyses discussed here, we anticipate  that Golitko and his team will discover this summer that obsidian was reaching communities on the Sepik coast well before ~3,500 BP.

Funding for this research was provided by National Science Foundation Grant No. BCS-1155338–”Archaeological and Environmental Investigations along the mid-Holocene shoreline near Aitape, Northern Papua New Guinea,” Mark L. Golitko and John E. Terrell.
References:

Borgatti, S. P., M. G. Everett, and J. C. Johnson. 2013. Analyzing social networks. Los Angeles: Sage.

Chappell, J. 1982. Sea levels and sediments: some features of the context of coastal archaeological sites in the Tropics. Archaeology in Oceania 17:69–78.

Cochrane, E. E. and C. P. Lipo. 2010. Phylogenetic analyses of Lapita decoration do not support branching evolution or regional population structure during colonization of Remote Oceania. Philosophical Transactions of the Royal Society B 365:3889–3902.

Embrechts, P. and M. Hofet. 2014. Statistics and quantitative risk management for banking and insurance.  Annual Review of Statistics and It Application 1: 493–514.

Girvan, M. and M. E. J. Newman. 2002. Community structure in social and biological networks. Proceedings of the National Academy of Sciences of the United States of America 99:7821–7826.

Golitko, M. 2011. Provenience Investigations of Ceramic and Obsidian Samples Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry and Portable X-Ray Fluorescence. In Exploring prehistory on the Sepik coast of Papua New Guinea, J. E. Terrell and E. M. Schechter, eds., pages 251–287. Fieldiana Anthropology New Series No. 42. Chicago: Field Museum of Natural History.

Golitko, M. and J. E. Terrell. n.d. Modeling cultural patterning and prehistoric interaction along the “inland” Bismarck Sea using network analysis. Unpublished manuscript, 2012 NEOMAP Project “Inland Seas in a Global Perspective,” Leiden, Netherlands.

Hope, G. S. and S. G. Haberle. 2005. The history of the human landscapes of New Guinea. In Papuan Pasts: cultural, linguistic, and biological histories of Papuan-speaking peoples, A. Pawley, R. Attenborough, J. Golson, and R. Hide, eds., pages 541–554. Canberra: Pacific Linguistics.

Irwin, G. J. 1992. The prehistoric exploration and colonisation of the Pacific. Cambridge: Cambridge University Press.

Specht, J., T. Denham, J. Goff, and J. E. Terrell. 2014. Deconstructing the Lapita cultural complex in the Bismarck Archipelago. Journal of Archaeological Research 22:89–140.

Summerhayes, G. R. 2009. Obsidian network patterns in Melanesia—sources, characterisation and distribution. IPPA Bulletin 29:109–124.

Terrell, J. E. 2004. The “sleeping giant” hypothesis and New Guinea’s place in the prehistory of Greater Near Oceania. World Archaeology 36:601–609.

Terrell, J. E. 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. The Journal of Island and Coastal Archaeology 5:3-32.

Terrell, J. E. 2010b. Social network analysis of the genetic structure of Pacific Islanders. Annals of Human Genetics 74:211–232.

Terrell, John Edward. n.d. Understanding Lapita as history. In The Oxford handbook of prehistoric Oceania, Ethan Cochrane and Terry Hunt, eds. Oxford: Oxford University Press.

Terrell. J. E. and E. M. Schechter. 2011.Archaeological investigations on the Sepik coast of Papua New GuineaFieldiana: Anthropology42:1–303.

Torrence, R. 2011. Finding the right question: learning from stone tools on the Willaumez Peninsula, Papua New Guinea. Archaeology in Oceania 46: 29-41.

Welsch, R. and J. E. Terrell. 1998. Material culture, social fields, and social boundaries on the Sepik coast of New Guinea. In The archaeology of social boundaries, Miriam Stark, ed., pages 50–77. Washington: Smithsonian Institution Press.

© 2014 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.

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.

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.

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.

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?

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