Nearly 10 million years ago, segments of DNA in the genome of a common ancestor of humans, gorillas and chimpanzees began to duplicate copies at a greater rate than in the past, contributing to diseases like autism and schizophrenia.

But that gene duplication also may be responsible for a genetic flexibility that has resulted in some uniquely human characteristics.

“Because of the architecture of the human genome, genetic material is constantly being added and deleted in certain regions,” says Howard Hughes Medical Institute investigator and geneticist Evan Eichler, who led the project that uncovered the new findings. “These are really like volcanoes in the genome, blowing out pieces of DNA,” he added.