Actually, Foster's rule indicates that predation being the main threat leads to smaller animals, while the restriction of resources being the main threat leads to larger animals.

> The same reason why the average man was 5 inches shorter in 1750 than he is today.

This is more likely dietary changes than resource restriction—we may not have had industrial farming, but the average person wasn't starving either. But you need access to plentiful, high levels of protein to maximize your height advantage.