A stroll down the personal growth aisle of the bookstore tells us, among other things, Why Men Don’t Listen and Women Can’t Read Maps.
Men are competitive, gadget-loving, status-seeking machines. Women are, conveniently, perfectly suited to nurture children, trade secretive gossip with one another and seek the love of Real Men™.
I’m a biologist who studies the evolution of sex differences. No matter how big the distance between Mars and Venus, (75,000,000 miles, since you ask) it’s nothing compared with the distance between folks who write about sex differences.
It turns out the galaxy is teeming with life. At one end of the solar system, let’s say on Uranus, lives a slow-moving biological determinist who uses big, blunt stereotypes to draw conclusions about what is “natural” in humans.
Determinists occasionally come out of their caves to write self-help books about multitasking women and men who can’t use pol … y … syll …ab … les.
The notion that there are two types of people, men and women, who come ready-customised for differently defined roles is rubbish.
On Mercury, at the other end of the solar system, the inhabitants of our most changeable planet believe all differences between men and women come from differences in experience, socially constructed by the stereotyped ways people treat boys and girls.
Mercurians have thrown the biological baby out with the sexist bathwater, preferring the incredible position that sex differences and gender have nothing to do with biology.
To believe this necessitates either willing ignorance or a complete failure of biological imagination.
For far too long, people whose job it is to think seriously and deeply about sex differences and gender have squabbled childishly, as though nature and nurture were mutually exclusive alternatives, and one side might eventually win the battle if only they yelled loud enough.
Research groups making real progress in understanding sex differences recognise that nature and nurture interact. Experience and socialisation change us by altering the biology of our brains and our hormones.
And biology, too, shapes culture in complex but predictable ways.
Studying sex differences in humans can be awfully difficult, because there aren’t many chances to compare people with similar biological histories but sufficiently different cultural practices.
That’s why a new paper in the Proceeding of the National Academy of Sciences of the USA has me excited.
Lead author Moshe Hoffman and his collaborators compared two tribes living in north-east India. The Khasi and Karbi peoples are genetically very similar groups of subsistence rice farmers, but they differ dramatically in one important cultural respect.
But the Khasi ban men from owning land, and men are expected to hand their earnings over to their wives. The youngest daughter in a Khasi family traditionally inherits the land from her mother.
Patrilineal systems such as those of the Karbi tend to give women much less power than men, in society as a whole and within individual homes.
Matrilineal systems, on the other hand, tend to give women roughly equal power to men (men seldom have less power than women).
Karbi daughters receive almost four fewer years of education than their brothers, but girls in the matrilineal Khasi villages are educated for as long as boys.
The authors recognised these two tribes present an excellent chance to explore how culture and education affect the gender gap in spatial ability – the gap claimed to underpin women’s lack of map-reading prowess.
They gave villagers a very simple four-piece puzzle and timed how quickly each person solved it.
It turns out that, in the patrilineal Karbi, men took an average of 42 seconds but women took around 57 seconds to solve the puzzle. But Khasi girls and boys did not differ significantly (35 and 32 seconds respectively) from one another.
The differences in both tribes were tied to differences in education. The more years a villager had attended school, the faster they solved the puzzle.
Such a simple experiment shows a persistent and common sex difference can entirely disappear in a culture where girls and their education are considered every bit as valuable as boys and theirs.
It subverts the idea that important sex differences are “hard-wired” (a shoddy metaphor that invokes clumsy early computers and should, itself, be consigned to the metaphoric junkyard).
The authors emphasise their results don’t contradict the notion of biological evidence.
You won’t find me among the ranks claiming that sex differences aren’t real or that “heredity cannot be allowed to have acted any part in history” as pioneering anthropologist Albert Kroeber asserted.
Instead, scientists who are open to the many subtle ways in which biology and culture interact will do well to explore the evolutionary conflicts of interest that create differences between women and men in power, economic contributions and education.
What happened to the Karbi and the Karsi to lead them down such different cultural paths?
It’s unclear, but let’s hope that when it comes to navigating our way around the galaxy, it won’t matter who’s holding the map.