Rapidly evolving bits of DNA helped develop the human brain

Many of the fastest-evolving sections of the human genome are involved in brain development. These rapidly changing segments of DNA may have played key roles in the evolution of the human brain and in our cognitive abilities. Chris Walsh at Boston Children's Hospital in Massachusetts and his colleagues studied sections of the human genome dubbed "human accelerated regions" (HARs). These stretches of DNA are virtually identical in many other mammals that have been studied, suggesting they have important functions – but they differ in humans, implying our evolution has changed them. Previous studies have identified 3171 possible HARs, but Walsh says it is unlikely that they are all important.