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.

We need another explanation for our big brains like we need a hole in the head

(source)

Something was definitely up, up top, once our bodies, down below, committed to walking and running upright.

It’s only after things got familiarly human in the locomotor anatomy--when we got long legs, non-grasping toes, and reconfigured butts--that brains started increasing beyond ape proportions.

For the first four or five million years of hominin evolution (from 7-2.5 million years ago) the story’s about bipedalism. For the last two and a half, it’s about encephalization. We've known this thanks to fossils for a while and genetic evidence is saying the same thing. It’s natural, then, for such a cerebral organism to wonder whether the two are connected.

As you hypothesize, you could go the technology route. Freed forelimbs, not necessary for locomotion, are free to be handy. O! the possibilities for hurling turds and building worlds! So that's one idea: Selection for a brainier hominin (both physically and cognitively) could occur only after the hands were habitually free to be freaky.

You could go the ecology route. Once our bodies committed to bipedalism our diet changed to include more meat, hominin body size increased, and geographic dispersal did too, no doubt aided by our more efficient bodies built for long distance travel. These characteristics, together, have been compared to those of scavenging and predatory carnivores. Regardless of how small or large a part meat played in our ancestors’ diets, there’s no denying that an ecological shift occurred in the early Pleistocene, with an increase in diet and habitat diversity, and that shift must have included new requirements of the brain.

Or, you could go the sociality route. As hominins relied more and more on cooperative foraging and parenting behaviors, etc, navigating social networks became key. Once complex speech and language arrived, then there would be new demands on the brain as well.

These pressures, requirements, demands, however you want to think of them, could be working in concert and at different times (e.g. technology plus socializing) over deep, geologic time and many many hominin generations. By "working," I mean contributing to the more-or-less sustained differential reproductive success of hominins with slightly larger brains. And because it’s the way that the fossil and archaeological records reveal behaviors over time, I tend to think of these three categories (technology, ecology, sociality) as describing the last 2.5 million years in the order I listed them. Technology was strongest earliest (starting with the Oldowan stone tools by 2.6 mya), and persisted. An ecological shift came along with that technological shift and then persisted. And of course social complexity came along with the technological and ecological shifts and then persisted.

These are some of the most mainstream hypotheses for encephalization (1) and they're implicitly or explicitly predicated on the prior evolution of bipedalism.

But now there's a new tie between big brains and walking upright--offered up in a  new paper just out in PNAS--and it's based in the human-, not ape-, like tendency to fuse the metopic suture later in life, to delay the close of what starts as a hole in the top of a baby's head known as its anterior fontanelle. The authors suggest that we need this hole in our head to exit our mother's bipedally-adapted birth canal safely and we also, as they suggest, need it to grow up to be an encephalized creature.

According to the authors, the "Taung child", an Australopithecus africanus kid (a member of a well-known bipedal hominin lineage) had an unfused metopic suture, left as an imprint on the fossil brain endocast.

Raymond Dart with the Taung child fossil.  http://en.wikipedia.org/wiki/File:Raymond_Dart_with_Taung.jpg 

Seven other australopith and Homo fossils are also described in the paper as having unfused metopic sutures. You might too! The odds are small, but since you started with a hole in your head as a baby, you could still be walking around with it unzipped.

To any chimps reading this, your metopic suture most likely closed just after birth and before your first deciduous molar erupted. But for 90% of humans (as reported in the paper), the suture closes later, after the eruption of the first deciduous molar. There’s a much slower fusion rate in humans than in chimpanzees.

However, to interpret the Taung child’s anatomy, things get a bit dicey, like things just love to get with hominin fossils. So often they can go either way: chimpy or humany.

Check out the figures below. A is for Pan troglodytes (common chimps) and B is for Homo sapiens. Those are frequencies of metopic suture fusion per dental age group. By listing them this way, instead of by chronological age, we're able to compare between two species that grow at different rates but share the same pattern of dental eruption. Chimpanzees grow up faster than us and experience earlier metopic suture fusion than us. Flipped around, humans grow up slower than chimps and experience delayed fusion of this suture compared to them. The Taung baby's dental age category is starred (*) at the "M1" stage in A and B. (The Taung child died at around 3.8 years of age, when its first permanent molar, M1, was erupted.)

Because it's more likely you'll find a human at that age (*) with an unfused metopic suture than a chimp, the researchers leaned toward calling the Taung child's state human-like, rather than ape-like. They backed that assertion up by listing seven other late Pliocene-early Pleiostocene hominins with unfused metopic sutures... it's a trend in the hominin lineage that begins with some australopiths, like the Taung child, they say.

"The presence of a still patent fontanelle and of a partially fused [metopic suture] in the Taung child, and the incidence of unfused [metopic sutures] in five adult and two other younger Australopithecus/ early Homo specimens is thus taken as evidence that a human-like pattern of late [metopic suture] fusion was already present in mid-to-late Pliocene gracile hominins."

Okay. Intriguing! But now we must explain!

[This is the part where, if you listen very carefully, you can hear the collective curmudgeonly groans from within and beyond the walls of paleoanthropology.]

Enter the new hypothesis for encephalization based on the late fusion of metopic sutures. The authors nod to two papers that offer "adaptively neutral" explanations for late metopic suture fusion but argue that the fossil evidence combined with the differences observed in chimps and humans beg for an adaptive explanation. (This tack is unsurprising given how paleoanthropology generally operates.)

The authors offer us three adaptive hypotheses to explain late metopic suture fusion:

1. Reorganization and expansion of the frontal neocortex (explains late metopic suture fusion)
Something about the changing and enlarging frontal cortex required changes to the cranial bones, how they form, grow, and fuse.

2. The difficulty of giving birth to large-headed neonates through birth canals that were reconfigured for bipedalism, the “obstetrical dilemma” (explains late metopic suture fusion)

The squishy neonatal head, thanks to the fontanelle,  "probably occurred in conjunction with refining the ability to walk on two legs," Falk (the lead author) said to the media. "The ability to walk upright caused an obstetric dilemma. Childbirth became more difficult because the shape of the birth canal became constricted while the size of the brain increased. The persistent metopic suture contributes to an evolutionary solution to this dilemma."

The trouble with this hypothesis as applied here is, although we know modern humans have a tight fit at birth now, there's little evidence for a tight fit between neonate and birth canal during australopith times.

And you can't help but wonder whether a squishy head was, or still is, required for successful birth. Do children suffering from craniosynostosis require a c-section to be born? Also, since the metopic suture fuses after chimpanzee birth, are we certain they aren't squishing their brains as they exit their relatively roomy birth canals? These questions may sound silly, but they're illustrating the built-in assumptions of the paper (or my ignorance about squishiness of baby heads).

The squishy head may be helpful during childbirth, but if it's occuring as early as australopith times, an adaptive explanation as a "solution" to an obstetrical dilemma is hard to swallow. That is unless DeSilva's estimates cited by the authors-- that australopiths had large neonates and tight fits at birth--are correct.

3. High early postnatal brain growth rates (explains late metopic suture fusion)
We know that humans have high rates of postnatal brain growth and this is what a lot of the news media picked up on: Your baby's head has gaps between the bones so the brain can grow like crazy after it's born to the gargantuan size of an adult human brain. As established in hypothesis #2, the need for the fontanelles in the first place is the crunch at birth thanks to the obstetrical dilemma, implying that without the pressure to be born small enough to escape the bipedal birth canal, we'd grow larger fetal brains in the womb.

So with this new paper we're presented with something even more fundamental than the notion that bipedalism as a necessary precursor for technological, ecological and social selection pressures for encephalization (as covered above): The tight fit at birth, caused by antagonistic selection for bipedal pelvic anatomy and large neonatal brains, created the selection pressure for a squishy neonatal head (which is facilitated by the fontanelles) and because of that roomy cranium, postnatal growth rates were able to ramp up in selective environments that favored encephalization.

So I'm left wondering, Do we need a hole in our head to be born successfully? Do we need a hole in our head to be encephalized? If the answer to both of those is yes, then what is a hole in the head doing in a hominin genus that may not have had much difficulty with childbirth and was hardly (if at all) encephalized? And, given the overlapping chimp and human fusion patterns, how can we be sure this feature on Taung is humany and not chimpy?

And, further, you can't (or at least I can't) help but wonder if there's a biomechanical/functional explanation for late metopic suture fusion, given how feeding behaviors and masticatory muscles put stress on the cranium. The skulls of australopiths and other hominins experienced stresses differently than chimpanzees. These differences may have begun as early as the nursing stage. Could this have anything to do with delayed fusion of the sutures? (here's just one study I found that addresses these kinds of questions)

And finally, it's hard not to link Falk (the lead author) to her research on Homo floresiensis. The hobbit (LB 1) looks like it has a fontanelle, something the disease-hypothesis folks point out is consistent with their perspective, and that’s one reason why I assumed these authors are onto this topic.

But LB 1 is conspicuously absent from the laundry list of hominin fossils in the supplementary section. Either they're saving what they've got on metopic suture and fontanelle anatomy in H. floresiensis for an upcoming paper or they just didn't think it was worthwhile to include this specimen. After all,  the latest paper on hobbit anatomy claims that the hobbit's "fontanelle" isn't real. Peter Brown writes, "direct examination of the asymmetrical hole in the posterior frontal of LB1, supported by CT scans, clearly indicates that this is the result of post-mortem excavation damage and is definitely not an unfused anterior fontanelle." (2)

Good thing, because if the hole in LB 1's cranium is of biological and not of taphonomic origin, then who knows how anybody'd explain its adaptive significance in such a tiny-brained hominin.

But, going way back to Taung and the australopiths: They were, after all, bipedal and the big brain train had to pull out at some point!

And, stay tuned. I got a tip from one of the authors about a paper coming out soon that demonstrates how weak the obstetrical dilemma hypothesis is, for explaining fetal size and growth, given the current evidence and given what we know about maternal metabolism.

Notes
(1) Of course, these hypotheses don’t represent all of paleoanthropology. I just intended to cover the major bases. And you need to consider what many paleoanthropologists assume which is that brain tissue is expensive so something extraordinary must have kept up selection on its increasing size for the last 2.5 million years. The assumption is that if brains were cheap, everyone would have big ones, but I don’t buy that. I think it's clear that other species aren’t encephalized because they don’t have to be. They do just fine without big brains. We have a rather warped perspective on selection for encephalization, thanks to our presentism and our big brains.
(2) Thanks to K. Baab for the tip.

Is tribalism genetic?

Philosophers have a word for the situation in which the available data aren't sufficient to allow a decision between competing theories. That is, when two or more theories fit the data equally well (or equally poorly). They call this underdetermination, and it can be applied to many situations. Many theories of causation in epidemiology are underdetermined, for example -- numerous studies support the view that asthma or multiple sclerosis or heart disease have a genetic cause, but there are also numerous studies showing that these diseases have an infectious origin. Global warming is another example -- is it man made or just natural cycling?

Anthropology seems to be the intellectual home of many theories of uncertain interpretation. Perhaps this is because human behavior and evolution are notoriously difficult to assign 'true' causation to. Are humans innately violent? Are the behavioral differences between men and women culturally determined? Why, if evolutionarily the important things in life are survival and passing on our own genes, do people commit infanticide, or blow themselves up in suicide bombings?

Some theories are not underdetermined, they are just plain wrong, but that doesn't stop them from having believers, even believers who claim that scientific evidence supports the theory. ID adherents, of course, would claim that much of the same data that evolutionary theorists use to support the common origin of all life on Earth instead point to a divine origin.

Anthropology can claim many unsupported theories, such as that humans are genetically programmed to fear snakes, or that West Africans are fast runners because they were cattle thieves millennia ago, and had to be able to run fast to escape with their quarry, but most of these are better placed in the category of evolutionary Just-So stories, rather than underdetermined theories. They might be true, but how would we ever know? Can we rule out all other reasonably plausible explanations? Given the vagaries and weird one-off happenings over large areas and vast numbers of generations, how can we rule out something we haven't thought of?

Some questionable theories can claim actual scientific evidence in their support, including the aquatic ape hypothesis that Holly wrote about last week. A number of such theories continue to have legs in the Anthropology realm, even with overwhelming evidence against them. One is the idea that the closest living relative to humans is the orangutan. This is a not only a minority view, but the molecular and morphological evidence in favor of the 'alternative' hypothesis, that chimps are our nearest relative, is overwhelming and has been for decades. Jon Stewart gave this theory probably as much credibility as it deserves on The Daily Show back in August. Mark Stoneking has a commentary on the orang hypothesis in this month's BioEssays, in which he nicely refutes the 'evidence' as published in a recent paper in The New Scientist. He concludes by saying:

Finally, what are we to make of the fact that a paper whose arguments about the relative value of molecular genetic versus morphological evidence for phylogenetic analyses can be so readily dismissed gets published in a peer-reviewed, scientific journal? An accompanying editorial offers the illuminating insight that the paper "... comments on a topic of such keen general interest and therefore may well gain wide attention in the scientific and popular press." That it did, as the journal's website proudly points to coverage of the paper in The New Scientist. The editors also admit that although the reviewers were not convinced by the paper, nevertheless it "...was felt to be a contribution worth putting out to the test of further scientific scrutiny," even "though "...this perspective might superficially appear to be nonsensical to the majority of molecular anthropologists and systematists..." Yes, sometimes the conventional wisdom is overturned, and alternative views do deserve to be heard - but if publication in a peer-reviewed journal is to have any meaning at all, editors and reviewers have a responsibility to ensure that well-established contributory evidence is not dismissed in a superficial way.

A second Anthropological controversy that won't die has to do with interpreting the fossil remains of hominins found not long ago on the Indonesian island of Flores. Named Homo floresiensis, the majority view is that these remains are of hominins who lived some 18,000 years ago, they were small, and various features identified them to the discoverers as hominins, but perhaps belonging to a separate species that evolved on Flores. Others have argued that the remains don't deserve species status, but instead represent humans who happened to have been microcephalic--that's a harmful disorder, not just a description. Among other reasons to doubt this interpretation, however, are the results of a comparison of these remains with skulls from modern individuals known to have been microcephalic. The fossils do not look diseased to these researchers, but indeed, this 'controversy' is starting to spawn other unlikely disease possibilities. At this point, it is starting to look as though the dissenters simply refuse to be proven wrong.

Why do unlikely theories like these thrive? As Mark Stoneking points out, marketing interests can keep some hypotheses alive that should have died long ago. But, so can egos and career interests and so on. Often, which theory one chooses among competitors depends on one's prior beliefs, which can mean that some pieces of information are overlooked in favor of other data that seems more supportive of one's favored theory.

Everybody loves it when the circus comes to town. The clowns. The elephants. The stilt-walkers, and the side-show freaks. Kids of all ages snap up the tickets. Sometimes the 'circus' is the annual anthropology meetings, where a room is packed to the point of people (not monkeys) hanging off the rafters to see the food-fights. Another kind of circus, often, are the popular science magazines and television programs. They do, after all, have to sell ads the way circuses have to sell tickets.

Sometimes, we have no real idea of how to interpret data that would allow us to choose a theory -- we've got thousands of years worth of data on violence in human societies, but just how would we conclusively determine whether the cause is genetic or cultural? We clearly don't know, or we'd have sorted this out long ago. And sometimes we don't know how to ask the question in a way that would get us closer to an answer -- we may be better at understanding the causes of diseases like asthma or heart disease when we're better at understanding complexity.

While most theories in a field like Anthropology don't have much direct impact on how people live their lives, this doesn't prevent people from clinging ferociously to one interpretation or another.

Are we tribal for genetic reasons, or is it cultural?