I've amended my earlier home run graph (from my earlier post) to show the following:
What is interesting to me is that, even though many of the leader marks at older ages are claimed by the top ten home run hitters (such as Sosa, Mark McGwire, Ken Griffey Jr., and Barry Bonds), all of the early leader marks are claimed by other players (names like Jimmie Foxx, Hank Greenberg, Mel Ott, and Joe DiMaggio). It's not like the modern-era players didn't get early starts either; most were playing by age 21 and in Griffey's case, by age 19. But all of them saw increases in productivity in later ages that defied earlier standards.
Could this increase in productivity be the product of just healthy diets and good conditioning? Well, maybe. I guess it's not [the] clear (or the cream) to me.