All in the family?

Natural History, March, 2003

In his search for differences between Neanderthals and modern humans, Juan Luis Arsuaga ["Requiem for a Heavyweight" 12/02-1/03] may have missed the importance of similarities. He thinks no Neanderthal genes have reached us, but why should we even assume genes specific to Neanderthals existed? Even though today we can readily distinguish, say, Europeans from Aboriginal Australians, their distinctive characteristics do not reflect unique genes. Different human groups simply have different proportions of certain genetic variations (such as blood types A, B, AB, or O). So some other kind of evidence of Neanderthal ancestry is needed.

Studying Pleistocene Europeans, my colleagues and I found a long history of gene flow between various populations, including Neanderthals. And in a study of anatomical similarities, we could not dismiss the possibility that half the ancestors of early modern Europeans were Neanderthals. Of course, evolution has continued to modify genes and anatomy, and there are no Neanderthals left. But Mr. Arsuaga might indeed be carrying that drop of Neanderthal blood.

Would a Neanderthal pass unrecognized on a New York subway? Probably. The artist Karen Harvey built up muscle and flesh around a cast of the skull of the 70,000-year-old La Ferrassie Neanderthal [see illustration below]. I wonder how many men as good looking as this fellow were straphanging this morning on the A train.

Milford H. Wolpoff University of Michigan Ann Arbor, Michigan

In my view, modern humans evolved in situ from Neanderthals in Europe, as they did from robust forms elsewhere. Furthermore, the two manifestations of human form could never have encountered each other, because only one existed at any given time.

Abundant archaeological research has shown that the in-situ refinement of late Mousterian tools gave rise to the toolmaking traditions of the subsequent Upper Paleolithic. The late so-called Neanderthals who made those tools were almost indistinguishable from the early "moderns"--the Cro-Magnons--who succeeded them. Moreover, Cro-Magnon teeth and degrees of robustness are exact equivalents of late Neanderthal teeth and degrees of robustness.

C. Loring Brace Museum of Anthropology University of Michigan Ann Arbor, Michigan

Juan Luis Arsuaga REPLIES: Neanderthals and modern humans were two morphologically different types. Their skeletal differentiation was substantially greater than that of closely related present-day species such as lions and tigers, which can interbreed in captivity but don't usually mix in nature. But even substantial morphological differences between two populations do not necessarily imply the populations are genetically isolated (unable to interbreed).

Neanderthals evolved in Europe from their Middle Pleistocene ancestors. Modern humans appear later in the European fossil record; either they evolved locally from the Neanderthals (as Mr. Brace states), or they came from elsewhere and replaced the Neanderthal "aborigines." I think the second scenario is the more likely. Nevertheless, Neanderthals and modern humans could have interbred locally on a small scale, and Neanderthals could thereby have contributed to the gene pool of the earliest modern human population in Europe. If the gene contribution was small, though, those rare Neanderthal genes would probably have disappeared in a few millennia, long before the present--unless the Neanderthal genes gave their bearers greater fitness. If the morphological differences between Neanderthals and contemporary humans resulted from different frequencies of the same genes, as Mr. Wolpoff states, those unique Neanderthal gene combinations have been lost.

But my two colleagues and I agree on something quite important: Neanderthals had a human mind. They had self-consciousness and language, engaged in rituals, made long-term plans. Some investigators divide all past and present beings into just two categories: they (creatures without a mind) and we (the present-day human species). I say Neanderthals were on our side of the line.