Killer whales and the mystery of human menopause

A study by Cambridge and Exeter universities has found a link between killer whales, pilot whales and humans - the only three known species where females stop breeding relatively early in their lifespan. Despite very different social structures between the three species, the research - by Dr Rufus Johnstone of the Department of Zoology at Cambridge and Dr Michael Cant of Exeter - shows that in each case females become increasingly genetically related to those they live with as they get older. Because of this, there is a motivation for older females to do what is best for the survival of those around them. This creates a 'grandmother' role, where the success rate of breeding in the group can be helped by older females sharing parenting knowledge and stopping breeding to allow younger females easier access to resources. The research, published in the Proceedings of the Royal Society B , is the first to provide a plausible explanation as to why these species in particular are the only ones in which females finish reproduction while they still have decades left to live. Dr Cant, from the University of Exeter's School of Biosciences, said: "It's always been puzzling why only humans and toothed whales have evolved menopause, while females in all other long-lived species continue breeding until late in life. "Although the social behaviours of the three menopausal species are very different, there is a common link: their social systems mean females become more related to those around them as they get older.