Chance and isolation gave humans elegant skulls [New Scientist]
Only chance kept us from looking like our crag-browed Neanderthal cousins. A statistical analysis suggests that the skull differences between the two species stems not from positive natural selection but from genetic drift, in which physical features change randomly, without an environmental driving force.
Some anthropologists had put the cranial differences down to natural selection arising from Neanderthals’ use of their teeth as tools, for instance, or from modern humans’ speech. To test if genetic drift could have been responsible instead, Timothy Weaver of the University of California, Davis, and colleagues compared 37 measurements of the skulls of various modern human populations with those of Neanderthals. After a comparison of the mean divergence between Homo sapiens and Neanderthals and the mean divergence among groups of modern humans, they conclude that genetic drift is responsible (Journal of Human Evolution, DOI: 10.1016/j.jhevo4l.2007.03.001).
The development of culture weakened the influence of the environment upon both Neanderthals and modern humans, says Weaver. But ultimately the two species drifted apart genetically when they became isolated from each other.
[From issue 2613 of New Scientist magazine, 24 July 2007, page 19]