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"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.
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.
"There's a sense we as humans have kind of peaked," agreed Greg Wray, director of Duke University's Center for Evolutionary Genomics.
Around this time, farming techniques began to spread out of Anatolia - now Turkey - across Europe and Asia, archaeological evidence shows.
The farmers themselves may have moved, or natives may have adopted words along with agricultural technology.
"No matter how we [changed] the analysis or assumptions, we couldn't get a date of around 6,000 years," says Gray.
"This kind of study is exactly what linguistics needs," says April Mc Mahon, who studies the history of languages at the University of Sheffield, UK.