WHY ARE THERE NO NEANDERTHALS?

Saturday, September 13, 2003

Our distant cousins the Neanderthals are an enduring mystery. Physically they resembled us, yet the available evidence suggests that their lives and their culture were very different from those of the modern species Homo sapiens that succeeded them in Europe.

Of all the Neanderthal mysteries, perhaps the greatest is this: What happened to them? One obvious possibility is that our ancestors killed them off.

But scientists who study the ancient history of our species say there are also plausible alternative explanations, with as yet no conclusive evidence to choose among them. Remember that when paleoanthropologists and their similarly minded colleagues talk about "modern" humans, they mean people of our species who looked pretty much like us, that is, they were anatomically modern, but who lived on earth as long as 100,000 years ago, possibly much more.

To a virtual certainty, they are our ancestors.

But anatomy is not all there is to being human. Were these people also cognitively modern, that is, capable of the same level of thought and reasoning as contemporary humans? Were they behaviorally modern, resembling people of today who live in similar hunter-gatherer cultures?

And if they were, how would we know?

Steven Kuhn and Mary Stiner, of the Department of Anthropology of the University of Arizona, in a paper they titled "Modern is as Modern Does," suggest we could look at how they responded to changes in their environment.

Contemporary foraging peoples, Kuhn said, use very different tools depending on where they live and what kind of food they eat. Only near the equator, Kuhn said, is it possible to rely on vegetable foods year round. The further away from the equator people live, the more their diet shifts toward hunting, and the technology they use to get their food varies accordingly.

Anatomically modern humans, from 30,000 to 12,000 years ago, fit this pattern remarkably well. In the north, they used elaborately worked bone and antler as raw materials for hunting weapons. Further south, and in the Middle East, archaeologists find more of such things as grinding stones and mortars and pestles to process grains and nuts.

The technology associated with Neanderthals between 150,000 and 35,000 years ago, is "very much more boring," Kuhn says. Wherever and whenever you look, it basically consists of sharp pointy stones.

Even armed with nothing more than sharp pointy stones, the Neanderthals were very effective predators of large game. In fact, for several hundred thousand years they were a very successful species, though apparently with low population densities and a very low growth rate -- which, as Kuhn notes, is probably a good thing for us "or the world would have filled up with Neanderthals a long time before modern humans ever evolved."

But they never adapted their diet to other resources that their successors exploited -- birds, fish, or small mammals such as rabbits. And having less developed weapons made hunting riskier. To put it another way, peaceful competition for rabbit stew and the dangers inherent in walking up to a wild bison and sticking it with a spear that has a sharp pointy stone on the end, are sufficient to do in the Neanderthals -- there's no need to think anybody related to us was actually violent.

Richard Klein, professor of anthropological sciences at Stanford, is among those reluctant to concede that interspecies violence played a role in the replacement of Neanderthals by Cro-Magnon newcomers. "There's no evidence for that," he said.

He believes there were genetic changes in the population of modern humans in Africa, starting around 50,000 years ago, that allowed them develop a more technologically sophisticated culture. That would account for the fact that after living in Africa for tens of thousands of years, this population spread into Europe about that time, and within a comparatively short time replaced the Neanderthals. The Neanderthals, he believes, "were precluded from behaving in a fully modern way because of their genes."

"Short" is a relative term, of course. The Neanderthals were established in Europe by 300,000 years ago and were alone there until 50,000 years ago. By 30,000 years ago, they were gone.

Alison Brooks, professor of anthropology at George Washington University, believes the cultural changes evolved gradually. Starting about 90,000 years ago, hunting technology in Africa began to diverge from the tools Neanderthals in Europe continued to use until the two populations met again. African hunters apparently had projectile weapons -- points mounted on a haft of some sort, like an arrow or a throwing spear -- which made hunting more efficient and much safer.

Whether the change in Africa was fast or slow, by the time modern humans from Africa met the Neanderthals in Europe, the technology gap was enormous. As Brooks said, "Modern humans won the arms race in a way that Neanderthals seem not to have imitated."

But did they win it by fighting? Perhaps they had no need to fight.