An ancient virus hiding in chimp DNA may explain why human brains developed differently

Humans and chimpanzees share almost all their genes, yet our brains took different paths. In a study published in Science Advances, researchers at Lund University in Sweden grew miniature brain models from human and chimpanzee stem cells and found that a gene called LINC00662 — active in the human models and important for early brain development — was completely switched off in the chimpanzee ones. The culprit: the remains of a virus that infected chimpanzees millions of years ago and left its DNA behind. When the team used gene editing to remove the viral remnant, the gene switched back on — a neat demonstration that evolution shapes species through which genes are active, not just which genes exist.