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 


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

Statistical probability vs. baseline plausibility

John Edward Terrell

WE ARE LIVING IN INTERESTING TIMES. Pundits are saying many of us in the United States are no longer able to distinguish between fact and fiction. Globally speaking and equally alarming, the world may be returning to the Dark Ages before the Renaissance when faith rather than informed skepticism ruled the day.

Figure 1. Despite evidence to the contrary, some today deny that the earth’s climate has changed radically since the start of the Industrial Revolution. Source:

Drill down below the level of popular journalism and social media chatter, and you will discover that even scientists today stand accused of undermining popular faith in facts & figures. Christie Aschwanden at FiveThirtyEight is one of many science writers reporting that scientists have apparently been using statistical tests of significance (in particular, p-values)[1] to decide how true their results may be and whether they should write up their findings for publication. Yet, as Aschwanden observes: “The p-value only tells you something about the probability of seeing your results given a particular hypothetical explanation—it cannot tell you the probability that the results are true or whether they’re due to random chance.”

Drill down yet deeper below the level of common everyday understanding and it turns out statisticians, too, are adding to our collective uncertainty about who and what to believe in. Apparently they no longer agree on how to do what they do, statistically speaking.[2] If they aren’t sure, how can mortals like ourselves decide who to believe and what’s what?

What’s to be done?

If it is true that sweet reason is on the wane in the world today, what can be done—borrowing from a recent presidential campaign—to make America think again?

A conventional response would be that we must buckle down and commit ourselves anew to paying proper attention to data—solid, down-to-earth facts & figures. Surely this isn’t such an impossible task? And to help us out, let’s not forget that modern statistical tests of significance—however contested nowadays they may be by professional statisticians—were developed by experts years ago to help us conclude whether we have enough facts on the table to decide what they are showing us. Therefore, shouldn’t combining due diligence for real facts with properly employed statistical testing be sufficient to get us past the current “post-factual” crisis?

Unfortunately such a seemingly self-evident way of confronting today’s reported decline in the quality of human wisdom and collective insight is not only too simple, but also naive. Here’s why.

The mind’s artful creativity

The biologist François Jacob—he shared Nobel Prize in Medicine in 1965 with Jacques Monod and André Lwoff—titled his 1982 book about evolution The Possible & the Actual.[3] This title seems misleading. Jacob is not advocating in the three beautifully written essays in this slim volume for a traditional no-nonsense view of science as the rock-solid quest for the actual—for truth and certainty—although in his preface he does say:

. . . human life always involves a continuous dialogue between the possible and the actual. A subtle mixture of belief, knowledge, and imagination builds before us an ever changing picture of the possible. It is on this image that we mold our desires and fears. It is to this possible that we adjust our behavior and actions. In a way, such human activities as politics, art, and science can be viewed as particular ways of conducting this dialogue between the possible and the actual, each one with its own rules.

Yet Jacob’s message for us is not as elementary as this statement may suggest. As a committed evolutionist, he has in mind a decidedly utilitarian view of this purported dialogue. In his own words:

In lower vertebrates, sensory information is converted into moto-nervous information in a rigid way. Such animals appear to live in a world of global stimuli closely linked to processes of appropriate responses, what ethnologists call “innate releasing mechanisms.” In contrast, in birds and even more so in mammals, the enormous amount of information coming from the environment is sorted out by sense organs and processed by the brain, which produces a simplified and useful representation of the external world. The brain functions, not by recording an exact image of the world taken as a metaphysical truth, but by creating its own picture.

From this perspective, therefore, asking how truthfully your brain is taking in the world around you is off the mark. The real issue is how usefully it is doing so. “The external reality, the ‘reality’ of which we all have intuitive knowledge, thus appears as a creation of the nervous system. It is, in a way, a possible world, a model allowing the organism to handle the bulk of incoming information and make it useful for its everyday life.”

The plausible and the possible 

Over the years since the publication of The Possible & the Actual, research in cognitive psychology and neuroscience has done much to clarify how—and how selectively—the human mind constructs what Jacob calls the particular “possible world” within which it dwells.[4] Seen from your nervous system’s point of view, the job we are doing when we are dealing with the world isn’t drawing the line, so to speak, between what Jacob called the possible and the actual, but rather between the plausible and the possible —between what our experiences have taught us to expect to find “out there” in the real world and what might possibly be there based instead on logic or fantasy rather than facts & figures (see fig. 2).

Figure 2. From your nervous system’s point of view, the task you are constantly facing when you are dealing with the world around you is where to draw the line between the possible and the plausible, not the possible and the actual.

If so, then as Daniel Kahneman and others have been saying for years, where we draw the line between the plausible and the possible depends not only on facts & figures bolstered perhaps by statistical analyses, but also on our previous experiences, biases, and prior assumptions about the world and how it works that may not only be all but impossible to put on the table but may not even be part of our conscious awareness.[5]


Headlines lamenting that many of us have seemingly lost the ability to distinguish fact from fiction may be catchy and provocative, but we know enough now about how the human mind constructs its sense of reality to conclude—along with Jacob, Kahneman and others—that paying proper attention to facts & figures is only part of the challenge we face nowadays. It can be argued that how science itself, for example, is conventionally done focuses too much on weighing hypotheses in the light of evidence, and not enough on where hypotheses, so to speak, come from in the first place (see fig. 3).

Figure 3. Science is not just an interplay between evidence and hypotheses, but also with the assumptions, beliefs, and prejudices that make some hypotheses seemly more worthy of study and experimentation than others.

The operative question we need to be asking these days, therefore, is not only the statistician’s old “p-value” question “Do I have enough evidence in favor of my hypothesis to reject the null hypothesis?” We must be attending also more than currently seems popular to the broader question “Why do I find my favored hypothesis plausible enough to spend time and money taking it seriously?”


[1] Nuzzo, Regina. “Statistical errors.” Nature 506, no. 7487 (2014): 150-152.

[2] Rodgers, Joseph Lee. “Moving in Parallel toward a Modern Modeling Epistemology: Bayes Factors and Frequentist Modeling Methods.” Multivariate Behavioral Research 51, no. 1 (2016): 30-34.

[3] Jacob, François. The Possible and the Actual. Pantheon, 1982.

[4] Pouget, Alexandre, Jeffrey M. Beck, Wei Ji Ma, and Peter E. Latham. “Probabilistic brains: knowns and unknowns.” Nature neuroscience 16, no. 9 (2013): 1170-1178.

[5] Kahneman, Daniel, and Shane Frederick. “A model of heuristic judgment.” The Cambridge handbook of thinking and reasoning (2005): 267-293.

Ascoli, Giorgio A., Matthew M. Botvinick, Richards J. Heuer, and Rajan Bhattacharyya. “Neurocognitive models of sense-making.” Biologically Inspired Cognitive Architectures 8 (2014): 82-89.

John Edward Terrell is Regenstein Curator of Pacific Anthropology at The Field Museum, Chicago, IL 60605. His latest book A Talent for Friendship: Rediscovery of a Remarkable Trait was published on December 1, 2014 by Oxford University Press. Email address: terrell[at]

© 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.

Logical seduction and historical delusion

John Edward Terrell

Please note: this commentary, recovered on 9-Jan-2017, was originally published in Science Dialogues on 20-Feb-2015.

In his acclaimed novel The Oxford Murders, the Argentinean writer and mathematician Guillermo Martínez engagingly shows how easy it is to hide the truth from others by getting them to think that a series of similar events—in this instance, a series of murders—is happening because, when taken in sequence, they appear to add up to a coded message that we are being taunted to decipher.

Judging by appearances, each murder apparently symbolizes one of the logical steps in a predictable sequence, just as most of us would probably agree that the next logical number in the familiar series 2, 4, 8, and 16 must be the multiple 32.  Perhaps, but as the philosopher Ludwig Wittgenstein famously observed, any finite sequence of numbers can be continued in a variety of different ways, not just in the one way that may seem reasonable (Biletzki and Matar 2006).

For example, the narrator, whose name we are never told, is asked early in this novel if he can figure out what is the next symbol in the odd series reproduced here as Fig. 1a.

Figure 1.
Figure 1. Alternative possible solutions
to Martínez’s cryptic symbol series.

Although Martínez never shows us the solution he has in mind (the narrator merely tells us later on that the answer is the number series 1, 2, 3, 4), we suspect those who find riddles like this one appealing are likely to say the solution shown in Fig. 1b is the right resolve:  an answer derived from the rules of symmetry (Fig. 1c). Yet in keeping with Martínez’s revealing observations about both logic and magic set here and there in this story, what if the proper solution is not so playful?

For example, what if the three symbols already revealed follow instead the alternative rule that one stroke equals 1?  If this were so, then the missing fourth symbol in this cryptic series would not be an “M” with a bar drawn horizontally through it (in keeping with our different rule, this strange symbol could stand instead for the number 5), but disconcertingly could be drawn either as a single stroke (Fig. 1d), or possibly as an inscribed circle, the letter “O,” or a zero (Fig. 1e).

Doubt as to the proper resolve of Martínez’s series of symbols illustrates Wittgenstein’s cryptic and oft-quoted remark:  “This was our paradox:  no course of action could be determined by a rule, because every course of action can be made out to accord with the rule. The answer was:  if everything can be made out to accord with the rule, then it can also be made out to conflict with it. And so there would be neither accord nor conflict” (quoted in:  Biletzki and Matar 2006).

I am not a philosopher, nor a novelist.  It seems to me, however, that Martinez’s tale and Wittgenstein’s remark both tell us something about ourselves, about how we are given to looking for similarities among things and events proving that what we are seeing makes sense not by chance but necessity.  It might even be argued that human beings are strongly predisposed to equate similarity with necessity.

This is why we need statisticians, however much statistics may sometimes seem only a cultivated way of lying for effect.  They keep us from foolishly jumping to the conclusion that similarities in appearance or similarities in effect are necessarily similarities of cause.

And in this regard, we need to remember that when statisticians say that something should be attributed to “chance,” they do not mean “without cause.”  Far from it:  the point they are making is that the cause (or causes) is not necessarily the one we think it is.

Note: These observations were originally published as the introduction in my chapter "Return to the entangled bank: Deciphering the Lapita cultural series" in Sheppard, P. J., Thomas, T., and Summerhayes, G. R., eds., Lapita: Ancestors and Descendants, pages 255-269. Monograph 28. New Zealand Archaeological Association, Auckland, 2009.

Biletzki, Anat and Matar, Anat, “Ludwig Wittgenstein”, The Stanford Encyclopedia of Philosophy (Spring 2014 Edition), Edward N. Zalta (ed.), URL = <>.


John Edward Terrell is Regenstein Curator of Pacific Anthropology at The Field Museum, Chicago, IL 60605. His latest book A Talent for Friendship: Rediscovery of a Remarkable Trait was published on December 1, 2014 by Oxford University Press. Email address: terrell[at]

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