Central Asia has always been a thoroughfare for tribes migrating between East and West; that much scientists knew. But exactly when these movements took place, and how big they were, had been a matter of debate. Now, a study of DNA from ancient skeletons in Kazakhstan helps clear things up.
Kazakhstan, smack in the middle of Asia, has witnessed most of Asia's mass migrations of the past millennia. Some 2700 years ago, the Chinese Hsiung-nu tribe traveled westward across what is now Kazakhstan. And the mysterious 2000-year-old, distinctly Caucasian-looking "blond mummies" of nearby Western China, and an extinct European language from the same area, suggest migrations in the opposite direction.
To find out what marks these movements had left on the genetic makeup of the region, a team of scientists from Spain, Italy, and the United Kingdom extracted bits of ancient DNA from skeletons from the warriors' burial mounds that dot the Kazakhstan countryside. Then they powdered single teeth from 36 skeletons ranging in age from 3300 years to 1500 years old and extracted tiny fragments of mitochondrial DNA (mtDNA), a marker commonly used for genetic typing of human populations.
As the researchers report in the 7 May Proceedings of the Royal Society of London, Series B, the oldest samples had a clear European signature, identical to mtDNA found in the Mediterranean. But from 2700 years ago onward, the East Asian influence becomes more prominent in the samples. Geneticist Carles Lalueza-Fox, one of the paper's authors, says that the DNA clearly confirms that the original population of Central Asia, which probably left the blond mummies and the relics of a language, was European, to be mixed with East Asian peoples only later.
The results are "clear-cut" and confirm the migration patterns researchers had supposed based on archeological evidence, says population geneticist Lounès Chikhi of the French national research agency CNRS in Toulouse, France. He adds that the new data could be a start for more detailed testing of models of migration in this "very interesting region."