Kristen Hawkes, University of Utah (IMAGE) University of Utah Caption In the late 1990s, University of Utah anthropologist Kristen Hawkes developed the 'grandmother hypothesis' that humans developed lifespans longer than other apes because prehistoric grandmothers helped feed their grandchildren after weaning, allowing mothers to have more children sooner and increasing the prevalence of grandma's longevity genes in the population. In a new study, Hawkes used computer simulations to suggest that grandmothering and increased human longevity led to a surplus of older, fertile men, which in turn led to the human characteristic of forming couples or pair bonds. Credit Lee J. Siegel, University of Utah Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.