The Walker was an old guy, too. I don’t remember any old Walkers.
Anyone who dies turns into a walker. Lots of old walkers, where the people early on diet of natural causes and turn.
Heck, that nursing home early on that Rick’s people found would have a problem with the residents turning and having more energy to attack people dead than when they were alive.
And you’d have the person falling over from a stroke, coming back and eating Jorhe.