Solving the Mystery of the Much-Maligned Neanderthals

For the first time in 5 million years, there is only one human species on Earth, a human evolution specialist noted on 10 October during a public lecture by the AAAS Dialogue on Science, Ethics, and Religion.

For most of hominid history, our zoological family has included multiple human species roaming the Earth simultaneously, said Ian Tattersall, curator of physical anthropology at the American Museum of Natural History in New York City. Tattersall and co-speaker J. Wentzel Vrede van Huyssteen of the Princeton Theological Seminary speculated during the lecture on the fate of the Neanderthal species. The common notion of Neanderthals as ignorant brutes is misinformed, Tattersall and van Hyssteen concluded.

"Many paleoanthropologists believe Neanderthals to be a bizarre and extinct version of ourselves," Tattersall noted.

The opinion that human evolution is a linear march from primate man to perfection is wrong, according to Tattersall.

Clearly, he said, "evidence indicates that Neanderthals represent a now-extinct species, with a separate status as an evolutionary being in their own right."

For laypersons, the word "Neanderthal" brings to mind many pictures. One implication, often applied unfavorably, describes a short-sighted, ignorant, slouching brute. People imagine Neanderthals based on their cultural preconceptions, Tattersall said.

This common depiction of Neanderthals as dim-witted brutes is unfair, and not supported by fossil evidence. After all, he said, Neanderthals were the most successful members of the other species of hominids living in Europe and Asia. At one time, many species emerged, but the Neanderthals gained sole possession of the Eurasian continent, displacing all their relatives in the process.

The territory was vast, with wide variety and a striking climate contrast. Neanderthals were a very adaptable species, able to cope with different environmental circumstances and enormous fluctuations in habitat. The sheer range of conditions where they managed to flourish, despite periods of extreme climate changes, indicate that they must have worn clothing to survive the cold temperatures, Tattersall said.

But our very remote hominid ancestors were very different from modern humans, and it has been known for some time that the genetic path doesn't directly connect Neanderthals with us today. The isolation of fragments of mitochondrial DNA shows that Neanderthal samples are all highly similar, with little genetic variation, and dissimilar from today's humans. Neanderthals and Homo sapiens most likely shed their common ancestor 500,000 years ago. They are divergent species, separated by a lengthy evolutionary history, Tattersall concluded.

The Neanderthals lived successfully in Europe and Asia for 200,000 years. Homo sapiens or Cro-Magnon trickled into the Neanderthal territory from Africa about 40,000 years ago, sharing the land for about 10,000 years. Then, suddenly, the Neanderthals were gone.

TWO COMPETING THEORIES

One theory, still held by some paleoanthropologists, is that the Neanderthals were absorbed into the Homo sapiens population, through interbreeding.

"Physical differences in the Neanderthal species were so distinct that they would have represented a completely separate species from Homo sapiens," Tattersall said. "There was no biologically meaningful exchange of genes between the two species."

The other theory is based on the idea of direct or indirect conflict through warfare or economic competition for resources. There is some evidence of contact between the two species, and it wasn't necessarily a peaceful co-existence.

Homo sapiens may have introduced disease to the Neanderthal population, much like the Spanish conquistadors did when they arrived in the New World.

In any event, modern humans are the sole surviving twig on a branching bush produced by evolution. We're not the pinnacle of a ladder that our ancestors climbed, according to Tattersall, but an altogether different experiment.

Two more free, public lectures will be offered this year by the AAAS Dialogue on Science, Ethics, and Religion. The next event, titled "Darwin's Cathedral-Evolution, Religion, and the Nature of Society," will take place the evening of 12 November. For more information, see http://www.aaas.org/spp/dser/seminar/future.shtml.

—Monica Amarelo

15 October 2002

Also, see "What Makes Us Human?" and a related story on "Religion and Burial Rituals."