SSS 2008-06-13（在线收听）

This is Scientific American's 60-Second Science, I'm Cynthia Graber. This'll just take a minute. 

If evolution weeds out detrimental traits, why do some seem to stick around? Well what's bad in our current environment may have been good in the conditions under which we evolved. New research indicates that even the tendency toward Attention Deficit Hyperactivity Disorder may have been beneficial under the right circumstances. The study was published this week in BioMed Central. Dan Eisenberg is an anthropologist at Northwestern University. He investigated two groups of the same tribe of Kenyans. One group still lives a traditional nomadic life style, and one recently settled in villages. About 20% of individuals in both groups have a genetic mutation that's associated with food cravings and ADHD. Eisenberg collected body mass index and height data of adult males. Those with the ADHD associated gene who were still nomads were better nourished than those without the gene. But those with the gene who'd settled down were less fit. The ADHD related gene may encourage behaviors beneficial for nomads. A boy with this allele might more effectively defend livestock or locate food and water sources. But maybe he wouldn't do so well at farming or sitting in a classroom. 

Thanks for the minute for Scientific American's 60-Second Science, and I'm Cynthia Graber.