DID NEANDERTHALS COME TO A VIOLENT END?

SCIENTISTS QUICK TO OFFER OTHER PLAUSIBLE EXPLANATIONS FOR THEIR DISAPPEARANCE

Thursday, September 11, 2003 (Fourth page)

Our distant cousins the Neanderthals are an enduring mystery. Physically they resembled us closely enough that we have chosen to call them by our own family name, genus Homo. 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. Several researchers discussed recent discoveries in this field at the annual meeting of the American Association for the Advancement of Science, held in Denver in February.

The panel's title was ``Revolution and Evolution in Modern Human Origins: When, Where, Why?''

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: Putting Paleolithic Behavior Variation in Context,'' suggest we could look at how they responded to changes in their environment.

Contemporary foraging peoples, said Kuhn -- who presented the paper -- use very different tools depending on where they live and what kind of food they eat. An Inuit seal hunter's tool kit has little in common with the implements of someone who gathers and prepares vegetable foods such as seeds and nuts.

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 as well. ``Diversity, complexity and the level of investment in tools increases with latitude,'' Kuhn said.

Anatomically modern humans in the late upper-Paleolithic era, 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 Mousterian technology of the middle Paleolithic, generally 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, to begin with, fish, or small mammals such as rabbits. In contemporary foraging societies, small game like this is often collected by women and children. If that did not happen in Neanderthal society, either it was less productive on average or the women and children were involved in the hunting of large game, which was risky. Either possibility could imply limited potential for population growth, especially in competition with modern humans.

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.

This thesis, like those offered by other panel members, is not necessarily wrong; indeed, it's quite plausible, given that competition would act over periods of hundreds or thousands of years and a small edge in survival could be telling. What's interesting is how earnestly the researchers seek explanations other than the brutally simple one.

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, adding that he didn't like to think about it either.

His view is that the population of modern humans in Africa, starting around 50,000 years ago, began rather abruptly to develop a more technologically sophisticated culture, in ways we can see from the artifacts they left. It might, he suggests, be the result of a genetic change related to cognition or to language, though that is difficult to demonstrate directly.

In any case, it 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 Neanderthal species was 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, Klein said, and he thinks the replacement probably happened much more quickly than that. Moreover, he says, if Neanderthals contributed any genes at all to modern humans, ``it's probably not detectable either in the fossil record or the genomes of modern people.''

If modern humans so quickly and successfully replaced the Neanderthals, he asks, why did they do it then, and not earlier? His answer is that earlier they were different and they couldn't, and that the change was recent and abrupt -- that is, in paleoanthropological terms. If the change had to do with spoken language, for example, it might still have taken thousands of years to select for the specialized changes in the anatomy of the mouth and throat that allow fluent speech.

Alison Brooks, professor of anthropology at George Washington University, agrees that modern humans expanded from Africa from 60,000 to 40,000 years ago, having lived there for 70,000 years before that.

But she sees the cultural changes as unfolding gradually during that time, until they reached a level that allowed the expansion to succeed.

She points out that there was an earlier exodus from Africa into the Near East, probably between 120,000 and 90,000 years ago, but it didn't succeed; Neanderthals reoccupied the area between 80,000 and 40,000 years ago.

Brooks bases her approach on the fact that modern humans -- including ourselves -- are distinguished from their predecessors ``by the extent to which we live in our heads.''

She means that we live in communities, societies, nations that are constructed in large part by human beings, not by nature, and that our daily lives and our connections to those communities ``are mediated by symbols, seen or spoken.''

But how would researchers find evidence of these capabilities in the archaeological record? ``Certainly animal images painted deep in a dark cave would count,'' she says, ``but what about a bead, a piece of ocher incised in a geometric pattern, or a grindstone used to crush red ocher into powder?''

One characteristic of contemporary societies is trade. ``We use and even depend on materials gathered or made by people we'll never meet through trade networks which act to form and reinforce social ties,'' Brooks says.

But the same was true in Africa long before modern humans expanded into Europe, she says. People in northern Tanzania imported obsidian from the central Kenyan highlands, a distance of more than 150 miles, as long ago as 130,000 years. In Europe, modern humans also used materials from distant sites, while Neanderthals typically used local materials.

``How far do raw materials have to travel before we think we're looking at trading networks and not seasonal migration?'' she asks.

Starting about 90,000 years ago, hunting technology for modern humans 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. They had bone harpoons for spearing fish. Also, the tools were regionally specialized across Africa.

Examples of decorative design such as shell beads begin to appear during the period before the expansion into Europe, another possible indicator of long-distance social networks maintained by trade. ``We don't need to resort to a genetic black box'' to explain the transition, since ``there is little or no evidence for a revolutionary change in behavior within a short period'' such as would be consistent with Klein's biological mutation theory.

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 didn't need to fight.