RedNova News - Science - Researchers Find Human Brain is Still Evolving

RedNova News - Science - Researchers Find Human Brain is Still Evolving: "Human evolution, University of Chicago researchers report, is still under way in what has become our most important organ: the brain. In two related papers, published in the September 9, 2005, issue of Science, they show that two genes linked to brain size are rapidly evolving in humans.
'Our studies indicate that the trend that is the defining characteristic of human evolution--the growth of brain size and complexity--is likely still going on,' said lead researcher for both papers Bruce Lahn, PhD, assistant professor of human genetics at the University of Chicago and an investigator at the Howard Hughes Medical Institute. 'Meanwhile, our environment and the skills we need to survive in it are changing faster then we ever imagined. I would expect the human brain, which has done well by us so far, will continue to adapt to those changes.'
Evolution, Lahn said, doesn't occur at the species level. Rather, some individuals first acquire a specific genetic mutation; and because that variant confers on those who bear it a greater likelihood of survival, it then spreads in the population. 'We're seeing two examples of such a spread in progress,' he said. 'In each case, it's a spread of a new genetic variant in a gene that controls brain size. This variant is clearly favored by natural selection.'
Lahn previously showed that there was accelerated evolution in humans among numerous genes, including microcephalin and abnormal spindle-like microcephaly-associated (ASPM). Both of these genes regulate brain size, and therefore 'were good candidates to look for signatures of selection. We indeed found such signatures when we compared humans to other species,' he said. 'As a natural extension of that, we asked, "