Calmly Considered, I Would Say Your Bottom Is Tops

by Michael Bell

Did Jack Lemmon say it to Shirley MacLaine in The Apartment? Research with chimpanzees has shown that they can identify other members of their group from pictures of their bottoms. Humans are really good at that: at an office picnic once in Moscow I noticed that almost everyone was wearing black jeans, so bored by the Russian chit-chat I could barely understand, I took photos of ten of their derrieres, deliberately using strange angles, and set a competition back in the office next day to see how many people could identify. The average score was seven, and one person got all ten.

Primatologists Frans de Waal and Jennifer Pokorny of the Yerkes National Primate Research Centre at Emory University in Atlanta, Georgia, asked six adult chimpanzees to link pictures of male and female chimpanzee behinds with photos of their comrades' faces. The chimpanzees scored well above chance, but only if they knew the individuals concerned - that's not too surprising, though.

The researchers say the test shows that chimpanzees use a 'whole body' method of storage and recognition, something that has been also demonstrated in humans (and in my office game).

In a further test, the researchers established that chimpanzees could identify the sex of a chimp face (no lipstick, promise!), but again only if they knew the individual, which shows, de Waal speculates, that the chimps recognise the sex of other chimps based, not just on physical attributes, but on other information from their previous experience with those individuals, such as their roles in the larger group.

If you think about how you identify the males and females you come across in non-gender-specific situations, I think you'll agree that we are not so different. Well, how would we be different?

Now for the interesting part: recognition of conspecifics should surely have origins way back in the phylogenetic tree? But how far back? Presumably recognition of known individuals is a given in any group setting. Dogs, birds, whales, for a start. Would they not then use the 'whole body' method? What about cockroaches? Intuitively you'll say not; but cockroaches have been shown to exhibit group behaviour. A cockroach has to be able to identify another one, and can presumably tell a male from a female - or is it done by pheronomes? Perhaps it's both - cockroaches live in the dark, a lot.

There are not many answers to be had. But time and time again it turns out that an ability we thought was special to us can in fact be demonstrated in quite remote species. 'Whole body' recognition is perhaps just such a case.



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