New U-M study suggests that's the way it was

ANN ARBOR–Two million years ago somewhere in Africa, a small group of individuals became separated from other australopithecines. This population bottleneck led to a series of sudden, interrelated changes–in body size, brain size, skeletal proportions, and behavior–that jump-started the evolution of our species.

That is the conclusion of a new University of Michigan study published in the current (January 2000) issue of Molecular Biology and Evolution that analyzes a broad range of genetic, fossil, and archeological evidence to decipher the most likely scenario for the start of human evolution.

The analysis, by researchers at the U-M Department of Anthropology, is the first to examine the full spectrum of paleontological, archeological, and genetic evidence available, each reflecting a different part of the puzzle of human origins. By estimating the ranges of error in the different types of evidence, the researchers were able to narrow down the common, overlapping areas of agreement to construct an explanation that disproves some high-profile recent theories and supports one of the oldest modern versions of the origin of homo sapiens.

"All the available evidence supports an 'Out of Africa' theory, that humans first evolved in Africa about two million years ago, then spread to other regions of the world," says John Hawks, first author of the paper and now an assistant professor of anthropology at the University of Utah. "This original population lived before humans colonized regions outside of Africa. In fact, it was the act of becoming human that made these colonizations possible."

Examining the anatomical evidence, the authors, including U-M anthropologist Milford Wolpoff, conclude that a "genetic revolution" took place in a small group isolated from other australopithecines. "The earliest H. sapiens remains differ significantly from australopithecines in
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Contact: Diane Swanbrow
swanbrow@umich.edu
734-647-4416
University of Michigan
9-Jan-2000