Some stereotypes are based on nothing, but studies have verified one generalization that we encounter in our daily lives: men tend to be better navigators than women. Though the phenomenon appears in a range of species, researchers don’t understand why it’s happening. Some guess that this male navigational advantage is adaptive—that men who could navigate wound up having more offspring than those who stuck close to home or got lost. But it turns out that is not the case, according to a new study published in The Quarterly Review of Biology .

Researchers from the University of Illinois looked closely at 35 studies on territorial ranges and spatial abilities in humans and a number of animals, including cuttlefish, deer mice, horses, laboratory mice, meadow voles, pine voles, prairie voles, rats, rhesus macaques and talas tuco-tucos (a type of burrowing rodent). In eight out of eleven species, the researchers found, males demonstrated moderately superior spatial skills than females.

This tendency applied regardless of territory size or the extent to which male ranges spanned farther than female ranges. This means that, even though females roamed just as much as males, they weren’t quite as good at it. If navigation really was an evolutionary advantage, females, too, should have been selected for equally superior abilities. The authors write:

We find no support for the hypothesis that species differences in home range size dimorphism are positively associated with parallel differences in spatial navigation abilities. The alternative hypothesis that sex differences in spatial cognition result as a hormonal side effect is better supported by the data.

In other words, hormones may be driving these differences. Navigational abilities may be a side effect of higher testosterone levels: previous studies have shown that women who take testosterone tend to see an improvement in their spatial navigation abilities.

The researchers warn that seemingly intuitive explanations, such as the men evolved brains better able to navigate, or that women undergo menopause so that they can spend more time nurturing their grandchildren, may appear to fit the bill but are generally difficult to test and verify scientifically.

Here, the researchers explain the logic behind their work:

If navigation emerged as an adaptive trait in men, it would also have emerged in women, unless it happened to be somehow detrimental to the fairer sex. As the researchers point out, however, “But how is navigation bad for women? This is a flaw in the logic.”

More from Smithsonian.com:

Have GPS Devices Taken the Fun Out of Navigation?

Superior Navigation Secret to Humans’ Success?