That human beings live longer than chimpanzees is something that we should thank grandmothers, according to an anthropological study coordinated by Kristen Hawkes, of the University of Utah (United States), and published in Proceedings of the Royal Society B. Their results are based on a computer simulation that mathematically supports the so-called "grandmother hypothesis" , proposed in 1997 and according to which when certain women survived past their childbearing age, they helped their daughters feed their grandchildren, they allowed their offspring have more offspring at shorter intervals because they did not have to feed the babies alone after weaning. In this way, long-lived grandmothers were passed on the genes that increased life expectancy to their grandchildren. Specifically, the new work shows that grandmothers' care for their grandchildren can increase life expectancy by up to 49 years in a relatively "short" evolutionary time period (from 24,000 to 60,000 years, according to simulations).
This does not happen to chimpanzees, as female primates live only a few years past menopause and thus die shortly after becoming infertile, without enough time to "be grandmothers."
