It’s those chimps again! Updated

They are on CNN and the NY Times, along with a press release R sent to us.  And before you get upset, notice that “fallacy” is used as a category for this post.

The NY Times tells us that young  female chimps play out a motherly role:

Young female chimpanzees like to play with sticks as if they were dolls, according to a new study in the journal Current Biology.

Although both juvenile male and female chimpanzees were seen playing with sticks in Kibale National Park in Uganda, females were more likely to cradle the sticks and treat them like infants.

Some chimps will even build little nests for the sticks.

CNN says

It’s just days till Christmas, and many young girls around the world will be thrilled to find little dolls under the tree to play with.

But there’s new evidence that it’s not only human girls who enjoy playing with imaginary babies — young apes may be showing the same behavior.

A research paper published Tuesday has found what its authors say is the first-ever evidence that young female chimpanzees in the wild “play” with sticks as if they are dolls.

“We find that juveniles tend to carry sticks in a manner suggestive of rudimentary doll play,” they write in the current issue of Current Biology. “And, as in children and captive monkeys, this behavior is more common in females than in males.”

Get it?  Being a mother is natural for female primates and the chimps show that.  So give up already on dolls for boys, unless they are soldier dolls or police and fireman dolls and other manly dolls like that.  From the press release:

The two researchers say their work adds to a growing body of evidence that human children are probably born with their own ideas of how they want to behave, rather than simply mirroring other girls who play with dolls and boys who play with trucks. Doll play among humans could have its origins in object-carrying by earlier apes, they say, suggesting that toy selection is probably not due entirely to socialization.

Here is the problem, however.  first of all, one and only one colony of chimps has been observed manifesting this behavior, according to the press release.  Secondly:

“We have seen juveniles occasionally carrying sticks for many years, and because they sometimes treated them rather like dolls, we wanted to know if in general this behavior tended to represent something like playing with dolls,” says Wrangham, the Ruth Moore Professor of Biological Anthropology at Harvard. “If the doll hypothesis was right we thought that females should carry sticks more than males do, and that the chimpanzees should stop carrying sticks when they had their first offspring. We have now watched enough young chimpanzees to test both points.”

But one person’s inference to the best explanation (which is what this quote may illustrate) is another’s fallacy of affirming the consequent.  To get the first and better label, we’d need to have some reason for thinking that it employs the best explanation or at least a very good one.  But does it?

Well, many feminists have argued that research like this simply borrows models from human behavior and then finds them (surprise!) in untutored nature.  But maybe there are quite different explanations.  We know that animals can copy one another.  (Anyone who dealt with the blue tit coordinated assault on bottle tops in England had evidence that birds can copy one another, and this can easily occur in social animals.  Blue tits are not born with bottle top lust.)  On the face of it, the stick carrying behavior has caught on in a group of female chimps.

For the behavior to catch on, there almost certainly has to be some reward.  It could be an inherited tic of some sort, but let’s suppose it is the result of copying rewarding behavior.  What would the reward be?

NPR talked to a primatologist at Emory University who advances an alternative explanation for different choices in young chimps and human children; it may be just a difference in energy conservation, with males more willing to expend energy in play:

Another primate researcher, Kim Wallen at Emory University in Atlanta, would like to see more evidence. For instance, Wrangham’s study includes a picture showing a young female chimp carrying a stick. Is she really cradling it like a baby?

A 9-year-old female chimp carries a stick, seen just below her left arm.

 

“This doesn’t happen to look like that to me,” Wallen says. “This looks like pausing to reconnoiter before shuffling off into the woods.”

As for whether that difference comes from biology or culture, Wallen prefers to say that biology produces a bias, which is channeled by experience.

“For example, the bias could be something as simple as increased energy expenditure in males and less energy expenditure in females,” he says.

But environment — and culture — could channel that difference in energy toward specific ways to play. And so we get trucks for boys and dolls for girls. Maybe, even, among chimpanzees.