The human genome has been busy over the past 5,000 years

A study now helps to clarify when many of rare genetic variants arose. Researchers used deep sequencing to locate and date more than one million single-nucleotide variants — locations where a single letter of the DNA sequence is different from other individuals — in the genomes of 6,500 African and European Americans. Their findings confirm earlier work suggesting that the majority of variants were picked up during the past 5,000 – 10,000 years. Researchers also saw the genetic stamp of the diverging migratory history of the two groups. The large sample size — 4,298 North Americans of European descent and 2,217 African Americans — has enabled the researchers to mine down into the human genome. The researchers were able to dig out genetic variants occurring in less than 0.1% of the sample population — a resolution that is a full order of magnitude finer than that achieved in previous studies. Of 1.15 million single-nucleotide variants found among more than 15,000 protein-encoding genes, 73% arose in the past 5,000 years.