This should make clear the foolhardiness of trying to identify causal factors – especially those from life experience – that are responsible for any given individual’s behavior.Jayman is a vociferous proponent of the importance of heredity and the correspondingly diminutive influence external environmental factors have on real world outcomes. That's what the data show, and that presumption wields Occam's Razor a lot more deftly than do all the modern epicycles that are applied (countless inconsistencies notwithstanding) in describing so many aspects of society.
It's important to keep in mind, though, that it isn't quite the whole story. There are threshold requirements--things that are necessary but not sufficient for realizing full potential--like nutritional sufficiencies, avoidance of severe physical injuries and avoidance of severely limited access to peers or exposure to language, etc.
Environmental factors need not only play a role by way of deprivation, either. After blazing a trail of destruction from modern Norfolk through to London, Boudica's bands upon bands of warriors, greatly outnumbering the Paulinus' single legion and its auxiliaries, were cut to pieces in the face of organized, disciplined Roman resistance. The ancient historian Cassius Dio:
Thereupon the armies approached each other, the barbarians with much shouting mingled with menacing battle-songs, but the Romans silently and in order until they came within a javelin's throw of the enemy. Then... they rushed forward and hit the enemy at full tilt so that at the clash they easily broke through the opposing line.It's recorded that 80,000 Britons died in the battle; just 400 Romans did.
The legionaries' famous steely discipline might, I suppose, have a hereditary behavioral component, but the martial ethos and military culture of the Romans probably account for lion's share of their advantage at arms, and it wasn't as though Celts and Gauls adopted into the legions were markedly less efficient than their Roman counterparts--they just needed to be trained. Even if corporal punishment doesn't get results today, decimation did.
There is a point to harking back nearly two millenia, though, and it's this: The freer, more mobile a society is, the more intractable differences in behaviors and outcomes are going to be. Attempting to eradicate all the incorrigible Gaps by aspiring towards a level playing field (as the Establishment often does by word if not by deed) is a strategy doomed to failure. In fact it'll only accentuate those gaps, not reduce them. It's easier to find truly behavioralist explanations in the past (and outside the WEIRD world) than it is in the present, and it'll be even more so in the future. Liberty and equality* are not complementary; indeed, to a large extent they're mutually exclusive.
Though most HBDers have the knowledge at hand to understand this, it's not always at the surface of their minds (it wasn't at mine until rather recently). It should be.
* Beyond isonomy and the conception of the spiritual, anyway