On a per capita basis, the highly intelligent became ten times more numerous in England between 1000 and 1850
Human populations have evolved over time, not only during prehistory but also well into recorded history. This evolution has affected a wide range of mental and behavioral traits: cognitive ability, time preference, propensity for violence, monotony avoidance, rule following, guilt proneness, and empathy, among others.
Such traits vary among human populations because different cultures have imposed different demands on mind and body. In general, the cultural environment will favor those who can better exploit its possibilities, just as the natural environment will. There has thus been a process of coevolution: we make culture, and it remakes us—by selecting those among us who survive to pass on their genes. This coevolution has proceeded along different trajectories in different populations.
The Great Cognitive Advance
American Buddhist Net 