Chimp Study Suggests Behavioral Differences Between Sexes Are Innate
Posted by Richard Conniff on May 12, 2014
One of the perennially raging debates in modern society has to do with the origin of male and female behavioral differences: Why are girls more verbal or more attentive to facial expressions? Why do boys like to compete in larger social groups and do risky things? Or as a parent might put it: Why is my daughter playing with dolls when she could be studying toddler astrophysics? And did my son really just chew his peanut butter sandwich into the shape of a gun?
On one side of the debate is the “men are from Mars; women are from Venus” argument that biology frog-marches us into our stereotypical gender roles. On the other is the “gender similarities hypothesis,” arguing that most of our supposed gender differences are small and show up only on average. In a phrase, “Men are from Minneapolis; women are from St. Paul.”
A recent study on chimpanzees, published in the journal Animal Behaviour under the title “Boys Will Be Boys,” comes down on the side of biology (but hold the frog-marching). Elizabeth V. Lonsdorf and her coauthors, including the celebrated primatologist Jane Goodall, looked at young male and female chimps in Tanzania’s Gombe National Park.
They focused on chimps two-and-a-half to three years old, when they are still infants but just starting to be weaned and a little less dependent on their mothers. (Both male and female chimps continue to travel and socialize with their mothers until they are at least eight years old, and they begin to spend the majority of their time away from her only at around age 10.)
Previous research on chimpanzees has found that adult females are less gregarious than adult males. The exception may be when they are sexually receptive. But they become less social again when pregnant and, as mothers, often spend much of their time accompanied only by their dependent offspring. Even one-on-one friendships—generally considered a female strength—seem to be relatively unimportant.
Adult males, meanwhile, spend much of their lives forming alliances, competing for status, and hunting in intensely hierarchical groups.
So how soon do these differences begin to show up?
Gender differences in socializing showed up beginning with the chimps’ “first independent forays into their social group,” the researchers write, with young females having fewer social interactions and particularly avoiding adult males, while young males sought out social interactions with adult males. Because mothers do almost all the child rearing and seem to show little difference in how they rear males or females, the implication is that these differences are innate.
More promisingly, for those who prefer an expansive view of female propensities, juvenile females tend to be better than males at tool use. In previous research at Gombe, Lonsdorf found that they pay more attention, for instance, when Mom is “termite fishing”—that is, dipping a stick into a termite mound and drawing it back up with edible insects attached. But they also pay close attention when she is making a nest, and they cradle sticks like baby dolls. Meanwhile, males are off roughhousing and acting foolish.
These gender differences make ecological sense, Lonsdorf explained in an interview. Young females need to pay attention to termite fishing and other forms of tool use. “It’s a less stressful way to get animal protein, because you can just plop down.” An adult mother carrying her baby for years at a time is not going to swing through the trees with male hunting parties in search of meat.
The new study looked at data recorded over 34 years of study and focused on 21 individual chimps. For each chimp, observers had spent at least 10 hours making notes once every five minutes on every detail of social interactions, mainly physical contact, grooming, and play. The study not only concludes that male and female social tendencies appear quite early in chimpanzees but also extrapolates these results to humans, close kin to chimps. “These data suggest,” the coauthors write, “that the behavioural sex differences of human children are fundamentally rooted in our biological and evolutionary heritage.”
The counterpart of young female chimps learning to use tools, said Lonsdorf, is that human girls tend to excel at an early age at fine motor skills like writing and drawing. Human boys, like male chimps, tend to excel at gross motor skills like running and throwing. Lonsdorf said that when she first started working at Gombe she was interested in tool use mainly to find out how chimpanzees learn. “But the sex differences kind of popped out.”
Since then Lonsdorf, a psychologist at Franklin and Marshall College, has become a mother of a daughter, now eight, and a son, age four. “I see them as chimps,” she admitted. “There are a lot of parallels to draw and not a lot of differences.” Her son “was born into a girl’s house, with girl toys, and Barbie dolls, and no trucks, no weapons.” When he first picked up a Barbie doll, she watched curiously to see how he would play. “He immediately started to beat the dog with it. He turned Barbie into a weapon.” Lonsdorf sat back, eyes wide, and thought, “Oh, this is a boy.” (Then she taught him not to hit the dog.)
“I frankly think it’s OK that male and female are built differently to be good at different things,” said Lonsdorf. “I think it should be celebrated.” The danger, she added, is that “people will latch on to it and say, ‘See, women should only have babies,’ ” or otherwise use it to excuse traditionalist prejudices or to exclude people from certain careers.
The opposite danger, among more progressive parents, may be to pretend that propensities don’t exist. Or worse, parents may want to train or punish them out of existence, banning dolls or weapons (or dolls as weapons) from the house. The new research suggests that a better approach is to understand where boys and girls are coming from and then use those propensities, without disparaging them, as a means of helping children achieve whatever their potential happens to be.
“I think one of the great things about humans,” said Lonsdorf, “is our capacity to recognize those differences but also realize that propensity does not determine ultimate capability. Yes, we’re built different, but we can all catch up if we want to. It’s a matter of education and will.”