Anthropology's troublesome arguments

By Anne Buchanan and Ken Weiss

These last few months have been strange ones for anthropology.  So much linen being aired so prominently, dirty and otherwise.  First we had a best-selling book by science journalist Nicholas Wade that in effect defines the field as the science of genetically determined traits, declaring among other things that there are five human races and that anyone who doesn't accept the biological basis of race is motivated not by science but by politics -- unlike his own stance. Then we had two papers (here and here) in PNAS suggesting that one of the now extinct short people on the Indonesian island of Flores had Down syndrome. And now we have a paper, albeit in a less visible journal than PNAS, but nothing's invisible to Twitter, declaring that premenstrual syndrome evolved to keep women from staying with partners with whom they are infertile.

The Wade book, of course, has gotten a lot of press, both positive and negative, including a letter in the New York Times last week refuting Wade's use of population biology by a long list of population biologists, many of whom are authors of the work Wade cites in support of his own political views, although of course he doesn't see it that way.  The PNAS papers got huge amounts of publicity around the world, but very accepting, none that we saw questioning the hypothesis. The PMS hypothesis, on the other hand, has been critiqued as nicely as 140 characters allow (including by Holly, who red-inks it below (it's a Twitter thing), and blames PLS (pre labor syndrome) for any perceived snark).

Each of these publications happens to bring up deep and long-standing issues in anthropology.  The issues involve the usual scientific food fights, but over and above the specific details, there are problems, and it's these that we want to discuss today.

Troublesome arguments
We'll take these issues one at a time.  Enough has been written about Wade's book that there's no need to look at the specific arguments again.  It's a continuation of retailing Just-So stories and selective reporting and misreporting, that he's been doing for many years; it sells well and he serves a surreptitious audience that includes various shades of racist enmity, as well as readers who have no way to know better, including many anthropologists.

Fine.  What's interesting to us, in terms of the broader field of Anthropology, is that it has clarified how deeply politics affects what we all make of scientific 'facts'.  You've got your genetic determinists on the right and your gene/environment interactionists on the left, and if you know how someone feels about genetic determinism -- that what and who you are is basically set the moment you are conceived -- then you know a lot about how s/he feels about IQ, scientific racism, natural selection vs drift, the importance of adaptation in evolution, and indeed about immigration, Obama, economic inequality, and so much more.  Sociopolitical views are correlated with what one seeks, accepts, or promotes when it comes to science -- not just some purportedly objective truth.

Genetic determinism is an interesting hot button issue.  Too often, people believe either that it explains virtually all traits or explains none, but of course it's some of both.  Some diseases, e.g., are caused with high predictability by a genetic variant, some diseases are due to gene/environment interaction, and some 'causal' variants are fairly useless for disease prediction.  Even infectious diseases that can affect almost anyone, that is, almost any genotype, do so in concert with genes.  Genes contribute to every trait, directly or indirectly: without genes we would not be here, and genetic variation can affect almost anything.  But that is not the same as saying that they determine, or specify, every trait.

There are academics who have trouble accepting strongly genetic arguments, because they believe they are, as the phrase goes, 'politically incorrect'.  But behind the political incorrectness smear is of course a dark history of eugenics, lynchings, the slaughter of 11 million people during World War II, including Jews, homosexuals, disabled people, and more.  But further, even if all of genetic-deterministic arguments were fully supported by the science, and we all were to accept that, for example, 'race' is a clear-cut biologically determined category of humans, why would that justify unequal, and worse, treatment of groups we (those in decision-making positions) deem unequal to ourselves?  Unequal because science tells us so.  Science doesn't make value judgements -- people do.  That is why the assertion of such points, or even the funding of studies to find them, is itself a political act.

To the people whose politics are supported by the new 'genomic' version of scientific racism (the latter term, we think, was invented in pre-Nazi Germany), of course, those arguments are 'politically correct' and their generally left-leaning proponents are just idiotic know-nothings.  Not in science, but in scientific racism, it's perfectly fine to cherry-pick the data when making an argument -- and the argument is supported by white supremacists, people who see genes behind everything, people who believe that every trait is here because it was naturally selected, and so on.  Genetic determinism and other labels have become code for accepting inequality, for hording resources, for rationalizing us having and them not having, and this often goes hand-in-hand with racism and hate (often not openly stated, of course, but sometimes it is). It's hard to argue that's science, not politics.  And, the disagreement won't be solved by science.

The problem here is simply the facile telling of stories without anything close to a sufficient understanding of the available information, the mixing of how things are today with how they got here, the assumption that how they are today is driven by genes rather than by much stronger and more ephemeral cultural factors, and the simple assumption that everything simply must be simply explained by genetic natural selection above other evolutionary paths.  In these conditions, a measured discussion of the issues is not possible -- and by the conflicting parties with their agendas, perhaps not even desired.

Getting to now may have nothing to do with then
The PMS paper is interesting for a number of reasons.  First, the author is a biologist who, at least judging from his web page, works on genetic variation in non-human organisms.  Mostly not even mammals.  So it's curious that he's decided to, er, wade into the evo psych realm.  Evo psych can be troubling enough when the arguments are coherent, so this one is particularly troublesome. In "Were there evolutionary advantages to premenstrual syndrome?" Gillings repeats and then discounts a number of previous evolutionary arguments about PMS, and then argues that premenstrual syndrome or premenstrual dysphoric disorder are essentially universal and experienced by all women, so there must be an adaptive explanation for such a maladaptive trait.  And of course it has a genetic basis.

Ongoing bonding between humans is complex, depending on sexual and nonsexual behaviours, and on previous experience in the relationship. Where such relationships do not result in pregnancy, premenstrual hostility may cause varying degrees of rejection, both sexually and of the relationship in more general terms. It might then be conjectured that infertile pair bonds are more likely to break down, freeing both partners to pursue fertile mates (Morriss and Keverne 1974).

Women suffering from PMS are likely to direct their anger at current partners, Gillings suggests, but most often it is when they have no children, that is, when one of the pair is infertile (or the pair, together, is infertile), that this will result in the dissolution of the pairing.

So, PMS evolved to dissolve infertile couplings.  But Gillings then says that this wasn't a problem in hunter gatherer times because women then weren't cycling nearly as frequently as women today -- they were pregnant or lactating, or poorly enough nourished that they didn't menstruate.  In that case, it's hard to understand how this evolved.  Gillings argues, though, that modern cycling is maladaptive, and that it causes health problems, as well as disrupts family dynamics with this genetically driven monthly bearishness of women.  He goes on to suggest that women should consider using cycle-stopping contraception (rather than, say, suggesting men should offer chocolate and not take it so personally).

But wait a minute.  First, a trait can only be selected if it's visible to natural selection.  It has nothing to do with whether people are paired up or happy (unless these are requirements for reproductive success, and the former is, according to some widely held evo psych-type assumptions), and it must be based on genetic variation, not cultural patterns.  If women weren't cycling regularly, and there's a lot of evidence that they weren't until modern times, how could PMS adaptively evolve if it didn't exist in any significant form?  And second, as Ken pointed out in his series a few weeks ago on the mythology of natural selection, there are many other ways that traits can evolve, including a series of reasons we might have no ability to guess, and including by drift relative to any Just-So story we reconstruct as if we got here in a straight adaptive line from then to now.

Like Wade's book, this paper makes the all-too-frequent mistake, in evo psych yes, but in anthropology -- and increasingly in other fields as well -- of assuming that every trait is adaptive, is here because of natural selection, and is thus genetically determined.  And that if we can build a plausible argument, it must be true.  And that the way it functions today is the reason for its evolution.  But, let's call this the geodesic fallacy.

SpaceTime trajectory real and imaginary (modified from GoogleImages)

See Ken's final post on the mythology of natural selection for the details, but here's the gist:

Even if the implicit complete determinism of Darwinian assumptions were true, the complex dynamic nature of earthly ecologies means that an evolutionary geodesic need not follow a retrospectively reconstructable path from then to now. A species or trait need not have evolved 'for' its current use, not even in stages aimed in a particular direction, not with its various components evolving synchronously or even sympatrically. Indeed, if and where ecologies are complex and dynamic, the meanderings of our object--a trait or species--may be essentially indistinguishable from random movement relative to any long-term 'purpose'.

It's very easy to make up adaptive scenarios.  That's why they are called Just-So stories.  And they are seductive.  But elegance or cleverness doesn't make them right.  Indeed, most often we have no idea if they are right, or even how to test them.

Again, the problem here is simply the facile telling of stories without anything close to a sufficient understanding of the available information, the mixing of how things are today with how they got here, the assumption that how they are today is driven by genes rather than by much stronger and more ephemeral cultural factors, and the simple assumption that everything simply must be explained by genetic natural selection.

Lumpers and splitters
The Flores controversy, of course, well-known in anthropology, has been ongoing since the first report of the findings of bones in Liang Bua Cave on the Indonesian island of Flores ten years ago.  The bones were from individuals obviously much smaller than other known hominids of the time, prompting the discoverers to declare them to be representatives of a species of human new to science.  The authors of the current re-interpretive papers on Flores at the time argued that no, these bones didn't represent a new species, but instead at least the one intact skull that was found represented an individual with microcephaly.  Now, it's an individual with Down syndrome.

LB1 skull: Wikipedia
 (associated postcranial remains can be seen here)

However, the argument is based on assuming that it's possible to definitively diagnose Down syndrome in a skeleton (among the many possible skeletal indicators of Down syndrome, most are not found exclusively in people with DS)  and that the asymmetry in the skull was present before the individual died, and not the result of thousands of years of burial, that this individual reached adulthood, and without modern medical care, that's less likely, all at least questionable assumptions.

But suppose LB1 really did have Down syndrome, then what?  Then it is completely irrelevant to any population or evolutionary argument.  One can argue about the Down diagnosis, a subject best left to actual experts of which there are many, but it matters not to the issue of whether the population experienced the very commonly observed evolutionary phenomenon of island dwarfism.

Cave where the bones were found: Wikipedia

This then gets into a very long-standing argumentation between those who tend to name each new fossil with a separate species designation (often called 'splitters' in evolutionary biology), and those who see a range of variation within species and argue that what we have found in the fossil record are representations of that variation, not of different species.  The latter are the 'lumpers'.  The snide and over-puffed Flores papers seem to be at heart a jab at those who see the Flores specimens as representative of a different species from the southeast Asian mainland.

Of course, 'species' is itself a largely subjective subject.  Even the idea of reproductive isolation is very hard to prove.  How many matings does one need to try to show that they never produce fertile offspring?  Usually, of course, and certainly with fossils we cannot do that directly!  The species problem has been debated for more than a century.

Were Neanderthals and early 'modern' Homo sapiens separate species?  Many would say so.  Are the recently prominent 'Denisovans', fossils from a region in Northwest Asia, a separate species?  They have separate names, after all!  Yet because they are recent enough, and perished under fortuitously helpful conditions, we have DNA from them.  And to date, the evidence suggests admixture between them (with remnants of both in modern humans today).  So: separate species, or not?

The arguments are heated among anthropologists about these sorts of issues and the more-heat-than-light regarding the Flores material reflects that.  There is, after all, a whole lot of publicity in the media for stories that sell, like tales of human fossils.  Anthropologists, whose field is often not all that rigorous given the problems of reconstructing the past, are particularly vulnerable to promoting their finds as different, or blasting their peers for doing so.  The media circus loves anthropologists, and anthropologists love it!

In these areas, the controversy is stirred up by the journals and the media.  Every week outrageously poorly supported evolutionary stories appear in journals and are eaten up by media reporters who either don't know the science, don't probe as they should, or don't care to be informed because the objective is to sell copy, and to do that content must be found.

Whether we'll see a day when appropriately measured questions can be asked and discussed, even if they can't really be 'answered', isn't clear.  Probably not in our lifetimes.