Fossils reveal human drift to 'beauty'

Rebecca Ackermann of the University of Cape Town, South Africa, and James Cheverud of Washington University School of Medicine, St. Louis, MO, measured facial features of the skulls of early humans and our ancestors. The scientists found that some characteristics of early human facial structure first developed as the result of natural selection from about 2 to 3 million years ago. This gave our ancestors "robust" faces with heavy brows and prominent jaws (see photo).

But things changed from about 1 to 2 million years ago, when our genus of apes, Homo, evolved. When this branch split away, the remainder retained their burly looks, while Homo developed a petite skull.

Ackermann and Cheverud assessed the pattern of variation both within and between the groups. They found that within the genus Homo there was a random pattern of variation among facial features. This suggests that genetic drift played more of a role than natural selection.

"Cultural inheritance could have released many of the morphological traits of humans from the pressures of stabilizing selection," Ackermann and Cheverud wrote, in Proceedings of the National Academy of Sciences.

What this means is that as human culture developed, we became sheltered from the raw strength of natural selection. We developed technology. At first, just stone tools, which were used to kill animals and chop them up. And when we started using fire to cook the meat, there was another relaxing effect on natural selection. Paleontologists tell us that both advances appear in the fossil record at about the same time as the genus Homo.

•	Fossils reveal human drift to 'beauty' Natural Selections The Japan Times (Japan), Thursday, Jan. 13, 2005 Byline: Rowan Hooper, Trinity College, Dublin