I recently had a very interesting discussion with a learned-friend, concerning the devastating consequences of two successive world wars on human genetics.
The recruitment of millions of young men (from many Continents), selected specifically for the best of intelligence, dexterity, aptitude, eysight, physical stature and health; only for most of them to die before they had a chance to pass on their genetic 'excellence'; means that many of we that were born since, effectively inherited second class 'excused from military service' (some might say 'reject') genes......I found the greater-concept quite thought provoking and more than a little sobering.