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http://www.nytimes.com/2005/09/08/s...age&adxnnlx=1126214557-4x6BjXUDUo/R/r1qSef2Gw
an excerpt:
"Last year Dr. Lahn, one of a select group of researchers supported by the Howard Hughes Medical Institute, showed that a group of 20 brain-associated genes, including microcephalin and ASPM, had evolved faster in the great ape lineage than in mice and rats. He concluded that these genes may have played important roles in the evolution of the human brain.
As part of this study, he noticed that microcephalin and ASPM had an unusual pattern of alleles. With each gene, one allele was much more common than all the others. He and his colleagues have now studied the worldwide distribution of the alleles by decoding the DNA of the two genes in many different populations.
They report that with microcephalin, a new allele arose about 37,000 years ago, although it could have appeared as early as 60,000 or as late as 14,000 years ago. Some 70 percent or more of people in most European and East Asian populations carry this allele of the gene, as do 100 percent of those in three South American Indian populations, but the allele is much rarer in most sub-Saharan Africans.
With the other gene, ASPM, a new allele emerged some time between 14,100 and 500 years ago, the researchers favoring a mid-way date of 5,800 years. The allele has attained a frequency of about 50 percent in populations of the Middle East and Europe, is less common in East Asia, and found at low frequency in some sub-Saharan Africa peoples.
The Chicago team suggests that the new microcephalin allele may have arisen in Eurasia or as the first modern humans emigrated from Africa some 50,000 years ago. They note that the ASPM allele emerged at about the same time as the spread of agriculture in the Middle East 10,000 years ago and the emergence of the civilizations of the Middle East some 5,000 years ago, but say any connection is not yet clear.
Dr. Lahn said there may be a dozen or so genes that affect the size of the brain, each making a small difference yet one that can be acted on by natural selection. "It's likely that different populations would have a different make-up of these genes, so it may all come out in the wash," he said. In other words, East Asians and Africans probably have other brain enhancing alleles, not yet discovered, that have spread to high frequency in their populations.
He said he expected more such allele differences between populations would come to light, as have differences in patterns of genetic disease. "I do think this kind of study is a harbinger for what might become a rather controversial issue in human population research," he said. But his data and other such findings "do not necessarily lead to prejudice for or against any particular population."
"
an excerpt:
"Last year Dr. Lahn, one of a select group of researchers supported by the Howard Hughes Medical Institute, showed that a group of 20 brain-associated genes, including microcephalin and ASPM, had evolved faster in the great ape lineage than in mice and rats. He concluded that these genes may have played important roles in the evolution of the human brain.
As part of this study, he noticed that microcephalin and ASPM had an unusual pattern of alleles. With each gene, one allele was much more common than all the others. He and his colleagues have now studied the worldwide distribution of the alleles by decoding the DNA of the two genes in many different populations.
They report that with microcephalin, a new allele arose about 37,000 years ago, although it could have appeared as early as 60,000 or as late as 14,000 years ago. Some 70 percent or more of people in most European and East Asian populations carry this allele of the gene, as do 100 percent of those in three South American Indian populations, but the allele is much rarer in most sub-Saharan Africans.
With the other gene, ASPM, a new allele emerged some time between 14,100 and 500 years ago, the researchers favoring a mid-way date of 5,800 years. The allele has attained a frequency of about 50 percent in populations of the Middle East and Europe, is less common in East Asia, and found at low frequency in some sub-Saharan Africa peoples.
The Chicago team suggests that the new microcephalin allele may have arisen in Eurasia or as the first modern humans emigrated from Africa some 50,000 years ago. They note that the ASPM allele emerged at about the same time as the spread of agriculture in the Middle East 10,000 years ago and the emergence of the civilizations of the Middle East some 5,000 years ago, but say any connection is not yet clear.
Dr. Lahn said there may be a dozen or so genes that affect the size of the brain, each making a small difference yet one that can be acted on by natural selection. "It's likely that different populations would have a different make-up of these genes, so it may all come out in the wash," he said. In other words, East Asians and Africans probably have other brain enhancing alleles, not yet discovered, that have spread to high frequency in their populations.
He said he expected more such allele differences between populations would come to light, as have differences in patterns of genetic disease. "I do think this kind of study is a harbinger for what might become a rather controversial issue in human population research," he said. But his data and other such findings "do not necessarily lead to prejudice for or against any particular population."
"
