The age at which you officially become an adult has been designated thanks to a poll of 2,000 Americans, with some saying it starts when you pay your own bills. The fountain of youth might be a myth but that hasn’t stopped the human race from seeking immortality, or at least a few extra years. Everything from the vegan diet to hanging like a monkey has been linked with decreased biological age estimates, and while most of us believe old age starts at 75, when do we become adults? Being an adult means less fun, the survey revealedIf you ask 100 people what age they became an adult, you’ll no do…