I'm an Apeman, I'm an Ape Ape Man
New data about australopithecenes vs. outdated imagery.
Posted Jun 03, 2011
I'll be your Tarzan, you'll be my Jane
I'll keep you warm and you'll keep me sane
That just about sums up the consensus view of gender roles that even the best of the mainstream media revert to whenever there is news about ancestral human history.
This week's example: press coverage of some truly exciting new research, published June 2 in Nature, about the geographic range of male and female australopithecenes in South Africa, ca. 2.2 to 1.8 million years ago.
The researchers, led by Sandi Copeland of the Max Plack Institute for Evolutionary Anthropology, set out to examine differences in the geographic ranges of two species, Australopithecus africanus and Paranthropus robustus, from the Sterkfontein and Swartkrans Cave sites. The method they used measures strontium isotopes in teeth. Strontium isotopes vary across different regions, and are taken up into the body through the plants and animals eaten. While bones are constantly remodeled, and thus change over the life course, teeth are not remodeled. So measuring strontium isotopes in teeth can indicate the environment where a person grew up, even after they have moved away.
Unfortunately for the original research design, there were no systematic differences in geographic range identified for the two species studied.
But the researchers did notice a pattern of differences between teeth of different size. Almost all of the larger teeth reflected strontium isotopes from within 50 km of the cave where they were recovered. But half of the smaller teeth reflected strontium isotopes from farther away. Assuming that our current understanding of size differences by sex among the australopithecenes is accurate, the larger teeth should be those of males, the smaller those of females.
It seems we need to amend the lyrics to Apeman a little:
I want to sail away to a distant shore and make like an ape woman
Predictably, press coverage of a study that violates normative assumptions has been somewhat less than illuminating. I collected a series of the most awful headlines:
Human ancestors were Mama’s boys
And my personal favorite:
I could easily have added to these. But you get the picture, right? The stay-at-home males are, variously, portrayed as being incapable of moving away from mom; as left holding the baby by their run-around girlfriends; or forming attachments to other males with whom they shared their "man caves". The emphasis on male behavior in these headlines is fascinating, since the real story here might have been assumed to be that females ranged more widely.
But with the exception of an AP story with the headline Wandering Women, the uniform emphasis of headline writers was on the male experience, and how it differed from an implicit image of the Ape Man.
It's easy to critique the more egregious of these articles; John Rennie, at The Gleaming Retort, does a great job with the Online Mail's version.
But as anthropologist Jason Antrosio of Living Anthropologically pointed out in a comment on my own Ancient Bodies, Ancient Lives, it isn't just the USA Today, Daily Mail, and similar media that recirculate outdated imagery in their articles on this story.
Take the coverage by Nicholas Wade in the New York Times. Antrosio points out that Wade "seems to most emphasize male dominance and hierarchy," as he says, "amplifying some very dated and debated assumptions."
The pattern of female dispersal is not unexpected, since it is practiced by chimpanzees, the closest living species to humans.
The reference to chimpanzees (and we can add bonobos) is warranted, not only because we share a common ancestor no more recently than ca. 5 million years ago, but because the authors of the study used this comparison in their own interpretation of their results.
Wade then goes on to argue that the data could be explained by aggressive territoriality:
A group of males who have grown up with one another is more cohesive and better at defending a territory against competitors.
Senior author Copeland is cited in some news stories as suggesting that the data might be explained by males needing to band together for defense.
But the article actually considers other explanations, suggesting the pattern could indicate:
Male australopiths had relatively small home ranges, or that they preferred dolomitic landscapes.
The Vancouver Sun suggests that there are divergent opinions about how to interpret the data among the researchers themselves:
U.S. anthropologists on the team are depicting the males as "stay-at-home-kind of-guys when compared to the gadabout gals."
Their British colleagues at Oxford University said the findings "suggests early cavemen had ‘foreign brides.'"
The imagery, again, is anachronistic, but informative. The British researchers, like the Times reporter, view things from the male perspective. Interestingly, the US researchers look at both the male and female experiences suggested by the differences in strontium isotopes.
The NY Times article leans heavily on the work of Bernard Chapais, covered in an earlier article by Wade. So, it rather rapidly turns from the empirical findings of the new research and the explanations the researchers themselves offer.
The isotope data are actually more complicated than the simple picture of males staying in their caves and females moving away would suggest.
Half (5 of 10) of the individuals with smaller teeth (presumed to be females) were not local to the cave where their remains were found, while most (8 of 9) of the larger toothed individuals, presumably males, were from the local range.
Our explanations need to account for the one nonconformist male who came from somewhere else. How could he fit into a model based on male solidarity and defense of territory (answer: not easily-- so maybe we should consider some other models...).
We need to develop models that take into account that half of the females were from the local area. This seems to be at odds with a simple model of female dispersal demanded by some reproductive imperative.
The tendency to oversimplify is endemic in human evolutionary models. It is a credit to the authors of the research that they propose mutiple possible explanations, which might explain different parts of the data. If we're going to anthropomorphize, maybe we could think a little more like the Kinks, and imagine our wandering ape man and ape woman having more complex motivations:
I think I'm sophisticated
'Cos I'm living my life like a good australopithecene
But all around me everybody's multiplying
Till they're walking round like flies man...
I think I'm so educated and I'm so civilized
'Tho I'm not a strict vegetarian
But with the over-population and inflation and starvation
And the crazy politicians
I don't feel safe in this world no more
I want to sail away to a distant shore...
(Paraphrase with apologies to the great Ray Davies...)