One of the biggest genetic differences between humans and other members of the primate family tree, including Neanderthals, predisposes people to a type of autism. The stretch of DNA appears to be an important piece of the human genome, but why?
University of Washington genome scientist Evan Eichler and his colleagues on an international research team focus on that question in a study published today by the journal Nature.
The key genetic structure consists of 95,000 molecular base pairs in a region on chromosome 16 that’s known as 16p11.2. The structure includes 28 genes, flanked by blocks of DNA with duplicated sequences of genetic code known as copy-number variants.
Eichler’s team compared the genomes of modern humans with the genetic code for chimps, gorillas and orangutans, as well as the code for Neanderthals and another strain of extinct pre-humans known as Denisovans. Humans were the only ones to have the structure in the 16p11.2 region.
The researchers’ analysis indicates that the structure appeared in our ancestors’ genome relatively suddenly, about 280,000 years ago. That time frame is about 80,000 years before anatomically modern humans – that is, Homo sapiens – show up in the fossil record.
“Most duplications in our genome are millions of years old, and the speed at which this structure transformed our genome is unprecedented,” Eichler said in a news release.