Glenn Carter Conroy

Weatherhead Resident Scholar


The Evolution of Humankind: A Modern Interpretation of Human Origins

The publication of Reconstructing Human Origins: A Modern Synthesis (Norton 1997), a textbook for upper-level and graduate students in paleoanthropology, coincided with author Glenn Carter Conroy's arrival at SAR for a spring semester residency. Conroy used his time at the School to work on a planned second edition that will incorporate molecular and genetic data that have become available since the book went to press and add a chapter on the human fossil record in the New World.

The recent DNA evidence Conroy has been working with relates to a current debate over human ancestry. "DNA in mitochondria, the little organels in our cells, are only inherited through our mothers," Conroy explained. "That means we can trace maternal lineages back through time. Anthropologists have been looking at the amount of diversity in mitochondrial DNA in modern human populations. Then, on the assumption that this DNA evolves at a constant rate, we can determine that all modern humans had a common maternal ancestor X number of years ago."

The so-called African Eve hypothesis, based on this technique, holds that all modern humans descended from a common ancestor who lived about 200,000 years ago in Africa. "But fossil evidence in China and Indonesia shows that humans lived in much of the Old World as far back as one million to one-and-a-half million years ago," Conroy noted. "If the Eve hypothesis is correct, it would mean that a small population in Africa evolved into what we consider Homo sapiens and then migrated out of Africa and replaced all the other humanlike animals. In contrast, the multiregional continuity model says that the whole Eurasian population together evolved into Homo sapiens between one and one-and-a-half million years ago."

A textbook, of course, must present both sides of a debate. "In this particular case," Conroy said, "I try to point out some of the assumptions and problems in the African Eve theory and suggest that we need to think about it rather than blindly accept it." Other debates Conroy covers include which of the apes is closest to humans, and what he calls "the gradual versus the jerky view" of how evolution proceeds.

Conroy's new chapter on the New World examines yet another heated controversy, the one between those who say there were no humans in this hemisphere before 12,000 BC and those who say there were. "Both arguments rest almost exclusively on carbon-14 dating, and there are many problems with that. For instance, how do we determine whether the 35,000-year-old charcoal found at a site in Chile is from a cooking fire or from a brush fire?"

"Anthropology has been plagued by polarization for a long time, and paleontology in particular has a long history of animosity between various camps," Conroy observed. "Being at SAR has been a wonderful opportunity for me to read the literature, synthesize it, make some sense of it, and try to present a nonpolarizing voice in these debates."

Affiliation at time of award:
Professor of Anthropology and Anatomy, Washington University Medical School, St. Louis

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