Sex-Based Roles Gave Modern Humans an Edge, Study Says

Stefan Lovgren
for National Geographic News
December 7, 2006
A division of labor according to sex and age gave modern humans an advantage over Neandertals, a new study says.

The emergence of "female labor roles" played an important role in human evolutionary history, because it allowed early-human hunter-gatherer societies to draw on more food resources and live in larger communities, researchers say.

It may help explain why the Neandertals (also spelled "Neanderthals"), who occupied Europe until modern humans arrived some 45,000 years ago, went extinct.

"The competitive advantage enjoyed by modern humans came not just from new weapons and devices but from the ways in which their economic lives were organized around … roles for men, women, and children," said Steven Kuhn, an anthropologist at the University of Arizona in Tucson.

Kuhn co-authored the study with University of Arizona colleague Mary Stiner. It appears in the December issue of the journal Current Anthropology.

Out of Africa

Some research has suggested that the practice of dividing labor according to sex dates back as far as two million years.

But the new study suggests the changes didn't occur until the upper Paleolithic period, which lasted from about 45,000 years ago to 10,000 years ago.

"We argue that the typical patterns of labor division emerged relatively recently in human evolutionary history," Kuhn said.

At sites dating back to the upper Paleolithic, researchers have found evidence of an emergence of skill-intensive crafts, such as bone awls and needles used to make clothes. They have also found small animal and bird remains.

As in hunter-gatherer societies of the recent past, men likely hunted large animals while women gathered small game and plants, enabling a more efficient use of available food sources.

When small game and plant foods were scarce, women and older children were often involved in other vital activities, such as producing clothing and shelter.

The researchers say this division of labor between sexes is likely to have arisen in a tropical environment.

It was a crucial evolutionary moment for modern humans and may have facilitated the spread of modern humans throughout Eurasia after leaving Africa some 60,000 years ago, the researchers say.

(See a map of early human migration.)

The scientists point out in their study that gender roles were not always the same in early-human cultures, and there's nothing that predisposes either sex toward certain kinds of work.

"That women sometimes become successful hunters and men become gatherers means that the universal tendency to divide subsistence labor be gender is not solely the result of innate physical or psychological differences between the sexes; much of it has to be learned," the authors write.

Big Game Hunt

The importance of specialized tasks is something the Neandertals apparently never learned.

Ancient Neandertal sites provide little evidence for any reliance on subsistence foods, such as milling stones to grind nuts and seeds.

Instead, the Neandertals, who lived in Europe from about 250,000 years ago until they disappeared about 30,000 years ago, preyed almost exclusively on large animals like bison, deer, and wild horses.

"This would have been a fragile system," the authors write. "In flush times, Neandertals would have lived high on the hog (or the red deer), but they may have lacked the kind of diversified resource base and labor network … needed to buffer them from major population losses in lean times."

Female skeletons found at Neandertal sites, like those of their male counterparts, have been shown to be robustly built, sometimes featuring healed fractures.

This suggests that the women didn't stay at home but joined the men in the often dangerous practice of hunting large game.

Wesley Niewoehner, an anthropologist at California State University in San Bernardino, has studied Neandertal hand mechanics.

"I've always been impressed by the observation that female Neandertal hand bones indicate that their hands were just as powerful as those of male Neandertals," he said.

"This indicates to me that female Neandertals were doing things with their hands that required significant physical force."

"Whether this fact means that female Neandertals were performing the same tasks as their male counterparts, or they were simply performing different tasks that required the same amount of force, is up for debate," he said.

"Nevertheless, this line of evidence does support an interpretation that the Neandertal sexual division of labor, or lack thereof, may have been fundamentally different from the division of labor in modern-human groups."

No Silver Bullet

John Shea, an anthropologist at Stony Brook University in New York State, says there is no single factor that explains the demise of the Neandertals.

"The risk we face when we have one very good study, like this one, is that people who don't appreciate the problem of variability in [Neandertal] environments over time will take this pattern and say ... this is why they went extinct: They didn't divide labor by sex," he said.

"Everyone wants to have one explanation, but it's not the way evolution works," he added. "It's never one simple cause."

Kuhn says his study expands the conversation beyond climate, stone tools, and animals bones to include social factors to explain the Neandertal demise.

"Anthropologists have known for a long time that the ways different human groups cooperate and manage their labor are as important to their success as the kinds of implements they use," he said.

The findings, he added, should not be taken as a justification for the separation of roles for men and women in contemporary society.

"We shouldn't look to the remote past for clues about how we ought to behave today," Kuhn said.

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