Men seem to have an uncanny knack for loading a half-dozen suitcases and knapsacks into even the smallest compact car, turning the bags like puzzle pieces to arrive at the most efficient fit.
Many men also can get behind the wheel and, even if they get a little lost, manage to steer the car in the right general direction.
Now anthropologists have shown in a new study that, as humans evolved, men with the best spatial skills and navigational aptitude could travel great distances, have children with multiple mates and thus pass on those skills to future generations.
University of Utah researchers tested and interviewed members of two African tribes, the Twe and Tjimba of northwest Namibia. They found, in keeping with findings from psychological literature, that men were better than women in spatial skills, as measured by computer tests such as one looking at the ability to imagine 3-D shapes on screens from different angles. Men were also better at pointing in the correct direction when asked where a certain village or landmark was.
But the study, published in the journal Evolution and Human Behavior, also found that men who were the best at spatial and navigational skills traveled farther over the course of a year. And men who covered more territory on their trips fathered more children — about 0.76 additional kids for every two additional locations they visited in the past year. It was the first time, the authors say, that the ability to travel far without getting lost was linked to reproductive success.
Members of the studied tribes live in mountainous, semiarid desert. They keep some goats and cows, grow maize and melons, and gather berries, tubers and honey. In the dry season, they set up camps in the mountains, where they forage. In the wet season, they move to camps near their gardens. They have a relatively open sexual culture, and many men have children with women other than their wives. Over the course of a year, members of the tribes cover about 120 miles. But men cover more miles than women, and the men who covered the most territory also had the greatest number of children by multiple mates.
"Modern foragers are very different from our ancient ancestors," says Layne Vashro, postdoctoral researcher at the University of Utah and first author of the study. "But some of their behaviors are models of the past. In terms of navigation, they're in a wide-open, natural environment, and they travel by foot — or by donkey."
Researchers tested members of the tribes from 2009 to 2011. Not only had the subjects never seen a computer before — they had never seen a map. "I've spent quite a bit of time with these guys now," says Vashro, who tested and interviewed up to 125 Twe and Tjimba men and women for the various study tasks. "They've been wonderful, accommodating and really nice. I was a bit skeptical about the computer tasks, but it went over really well. It's impressive how quickly people who've never seen a computer were able to pick up these tasks." And when he showed them maps, they would quickly recognize how the lay of the land they traversed on foot translated to images on paper.
Researchers found that men are better at manipulating objects in their minds, and that ability is related to navigation skill. They seem to be able to build a map of their world in their minds, says Vashro, perhaps mentally manipulating landscapes from different angles to keep track of how to get back home. That may have allowed early humans who were best at these skills to venture out in pursuit of more mates. The new study provides preliminary evidence of that theory. "We do have the finding that men who are traveling farther have more mates," says Vashro. He'll be involved in further studies of people in Namibia as well as Tanzania and Ecuador to see if the link between spatial skill, navigation skill and reproductive success holds up.
Does any of this shed light on a persistent question among couples in the developed world: If men are so good at navigation, why, when they lose their way, are they reluctant to ask for directions? "Men are also less anxious and more confident about the tasks," says Vashro, adding with a laugh that "their advantage in confidence, I believe, is greater than their advantage in ability."
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