The work was funded by the Howard Hughes Medical Institute. A family tree of Indo-European languages suggests they began to spread and split about 9,000 years ago.The finding hints that farmers in what is now Turkey drove the language boom - and not later Siberian horsemen, as some linguists reckon.Years later, a ruler declares one of those copies the definitive manuscript, and a rush is on to make many copies of that version — so whatever changes from the original are in this presumed important copy become widely disseminated.Scientists attempt to date genetic changes by tracing back to such spread, using a statistical model that assumes genes have a certain mutation rate over time."A different way to look at is it's almost impossible for evolution not to happen." Still, the findings also are controversial, because it's far from clear what effect the genetic changes had or if they arose when Lahn's "molecular clock" suggests — at roughly the same time period as some cultural achievements, including written language and the development of cities.Lahn and colleagues examined two genes, named microcephalin and ASPM, that are connected to brain size.
"There's just no correlation," said Duke's Wray, calling education and other environmental factors more important for intelligence than DNA anyway. The information contained in the AP News report may not be published, broadcast, rewritten or redistributed without the prior written authority of The Associated Press."We, including scientists, have considered ourselves as sort of the pinnacle of evolution," noted lead researcher Bruce Lahn, a University of Chicago geneticist whose studies appear in Friday's edition of the journal Science."There's a sense we as humans have kind of peaked," agreed Greg Wray, director of Duke University's Center for Evolutionary Genomics.Those criticisms are particularly important, Collins said, because Lahn's testing did find geographic differences in populations harboring the gene variants today.They were less common in sub-Saharan African populations, for example.That the genetic changes have anything to do with brain size or intelligence "is totally unproven and potentially dangerous territory to get into with such sketchy data," stressed Dr.Francis Collins, director of the National Human Genome Research Institute."The genetic evolution of humans in the very recent past might in some ways be linked to the cultural evolution," he said.Other scientists urge great caution in interpreting the research.Aside from not knowing what the gene variants actually do, no one knows how precise the model Lahn used to date them is, Collins added.Lahn's own calculations acknowledge that the microcephalin variant could have arisen anywhere from 14,000 to 60,000 years ago, and that the uncertainty about the ASPM variant ranged from 500 to 14,000 years ago.