Human beings age faster at two points in their lives, scientists have found and it makes middle age not so fun. A new study by Stanford University and Nanyang Technological University in Singapore showed that humans have two faster bursts of aging at a molecular level at the ages of 44 and again at 60. Research showed that aging happens this way rather than in a consistent, linear fashion. At those two ages, the ability to metabolize caffeine and alcohol notably decreases, and they see more muscle injuries and fat accumulation.