Wednesday, December 22, 2010

Chimps Love Our Sticks

Tell it, Echidne:
I have noticed a clear trend during my years as a blogger. Anything vaguely smelling of science which supports traditional gender roles immediately develops humongous wings and flies all over the place, crapping on our upturned faces.
She's talking about a new chimp study in Current Biology, now viral, that purports to show that gender roles in modern human children (girls like dolls, boys like trucks) are hard-wired, rather than cultural. Researchers studied a community of chimps in Uganda, and observed that more juvenile females than males engaged in "stick carrying" behavior that (very loosely) resembles maternal care-giving. In the words of the study's co-author, Richard Wrangham, "What we've got here is evidence that without any kind of socialisation by adults, females seem to be predisposed to react to sticks as though they were dolls."

This is true, in the sense that the sun "seems" to go around the earth, or that sticks "seem" to bend when you plunge them into water. But none of the evidence presented by Wrangham and his co-author Sonja Kahlenberg actually supports this "predisposition." It's a short study, hardly needing my summary, and you can read for yourself that every case of "sex difference" in stick-carrying could just as easily be explained by cultural, as by genetic factors. In fact, given that stick-carrying has not been observed in any other chimp community, the cultural explanation is far more plausible.

What is most striking about this study (apart from how ardently it is being embraced by the popular and social media), is how lax the researchers' reasoning is: Since mothers don't carry sticks (the behavior ceases after a female's first birth), young females can't learn stick carrying from them. Thus, the behavior is instinctive, QED. But there are a number of alternate ways that stick-carrying can be a cultural development. The young chimps can learn it from adult chimps who are not yet mothers, for example, or from older siblings.

But more to the point, it is also plausible that young chimps devise the stick-carrying behavior as a symbolic expression of the maternal act. They don't need to be taught a specific behavior for it to be considered cultural (and the wide variety of "sticks," including "pieces of bark, small logs or woody vine," militates against this being a question of following instructions.) Nobody, for example, taught mother chimps Vire and Vuavua to carry around the corpses of their children, after they died of respiratory disease. And neither would we be quick to say that carrying around your dead infant, grooming it, chasing away flies, was some kind of biological adaptation. (Though it might be).We aren't limited to attributing behavior--human or primate--to strictly passive, mechanical reactions, whether they be rote mimicry, as the behaviorists would have it, or instinctual imperatives, as nativists would have it. We are also empowered to characterize these creatures as actively, creatively engaging with their environment.

There's no real hypothesis testing in the stick-carrying study, just faux-scientific dressing up of a dull and unreflective belief in gender determinism. Studies like these come and go. But as Echidne notes, it's not bad science we should be worried about, but bad journalism. Nobody seized on the report, 3 years ago, that female chimps, not males (in roughly the same female-to-male ratio as in this stick carrying study), were the primary tool users, weapon users, problem solvers, and teachers. It just wasn't newsworthy, for some reason.


E said...

I'm not as passionate on this issue as Echidne is, in terms of gender roles... but I've often had the thought that scientists should not be allowed to publish until they get a philosophy consult on what the data means.

How often do we see a study, or some sort of scientific discovery of fact, followed by conclusions / speculation on what that means, which simply doesn't follow at best and is pretty stupid at worst?

Certainly not always true, but even great scientists are notoriously bad philosophers.  I'm thinking of Whitehead cleaning up after Einstein here.

underverse said...

I'd settle for a readier recognition that there is a profession trained to work out the philosophical implications of scientific statements. But in this case the reasoning is so bad, you don't need a philosopher to see it. Any responsible journalist should be able to spot the flaws.

E said...