I agree and disagree. Myself, in good shape at 21 was 6' 2" 275 (working for an excavating company, hitting the gym). Granted I was nowhere near an nfl talent, I was significantly larger (and in better shape) than any of my uncles or father ever was (significantly higher weight/bigger frame). My son (granted only a year old) is wearing 3t clothes with size 9 feet...maybe there is something to all those clamoring about hormones in cows milk...
That said I am now out of shape and near that in shape number...but working on it. And the little guy just keeps growing...
Edit: I guess what I'm getting at is the following generations simply seem to get larger and larger. While I don't disagree with the questioning of high, etc, some may just be what we are doing to ourselves through the mangled process of our diet. Chicken, beef, turkey all receive various hormones and altered feed, and that's what we eat...