American Scientist

To the Editors:

If the proposal of Thomas Wynn and Frederick L. Coolidge in "A Stone-Age Meeting of Minds" (January-February) is correct in locating the development of modern executive functions in Homo sapiens to the period 40,000 to 32,000 years ago, then a hypothesis would seem to follow naturally: The Neandertals themselves, through the stiff challenge they presented, are responsible for stimulating in Homo sapiens the rapid development of the latent genetic potential for modern working memories.

The critical period for the cognitive breakthrough is framed, in the article, from the arrival in Europe of Homo sapiens around 40,000 years ago and their encounter with the residing Neandertals, to the appearance in the archaeological record, 8,000 years later, of the first manifestations of executive functions based on working memories, attributable only to Homo sapiens. By 2,000 years after that, for uncertain reasons, the Neandertals were extinct. The authors propose a genetic dynamic for the 8,000 years: gene(s) for enhanced working memory, sparsely present in the Homo sapiens population 40,000 years ago, increased in frequency to the time, around 32,000 years ago, when the material effects first can be identified. Wonderful thinking! But why exactly then? The explanation would seem to lie, at least partly, in the Neandertals themselves. For Homo sapiens, with a prehistory of much success over others of the animal kingdom, the Neandertals represented a heightened level of competition—Neandertals, after all, had won out in the earlier encounter between the two species in the Near East 80,000 years ago. In Europe 40,000 years after that, Homo sapiens and Homo neandertalensis once again collided in "the most dangerous game," a challenge that would tend to foster in Homo sapiens—and in a hurry—selection for the relatively recent mutation(s) with advantageous cognitive potential, proposed by the authors.

Yvonne Korshak
New York, NY

Drs. Wynn and Coolidge respond:

The idea that the interaction between Neandertals and modern humans provided an impetus for cognitive development has in fact been proposed by Francesco d'Errico, Joao Zilhao and colleagues in Current Anthropology in 1998 and more recently by John Shea in Evolutionary Anthropology in 2003. They have emphasized that such interaction would certainly have cut both ways, providing an equally challenging selective problem for Neandertals. From the perspective of our hypothesis, of course, the modern humans would have carried in their gene pool an evolutionary potential not carried by Neandertals—the alleles for enhanced working memory. In this sense Dr. Korshak's suggestion is provocative. We are, however, reluctant to embrace it wholeheartedly. The chronological mismatch between the arrival of modern humans in Europe at about 40,000 years ago and the earliest convincing evidence of enhanced working memory at 32,000 may turn out to be an accident of the archaeological record. As we tried to stress in our original article, the enhancement of working memory capacity would not have left many traces, and there is a very real possibility that the earliest archaeological trace post dated the earliest behavioral manifestation by a significant degree. We do not think such reasoning would allow for a gap of tens of thousands of years, but a few thousand years is within the realm of possibility.