That was a problem I brought up in discussing the second season of the show, with people wondering if the fuss over Carl & Sophia was worth it. I pointed out the general trend of the ages of the characters in the group and how much trouble they'd all be in if their lifestyle depended to heavy physical activity or a degree of great physical strength ten years from now. The group at that point would have included Glen & Maggie & Beth in their thirties, and Carl & Sophia just hitting adulthood, while Rick, Shane, Lori, Andrea, Dale, Herschel, Carol, Daryl, T-Dog and all the casualties from the farm whom I can't remember anymore are in their fifties or worse.