The blogger explores the work of Cambridge anthropologist J.D. Unwin, specifically Sex and Culture (1934). Unwin studied 80 primitive tribes and six known civilizations through 5,000 years of history. He claimed there is a positive correlation between the cultural achievement of a people and the sexual restraint they observe (Wikipedia).
A causal relationship between chastity and the success of cultures remains (I think) to be established, yet Unwin’s correlations are compelling. The blogger lists a few:
Effect of sexual constraints: Increased sexual constraints, either pre or post-nuptial, always led to increased flourishing of a culture. Conversely, increased sexual freedom always led to the collapse of a culture three generations later.
Single most influential factor: Surprisingly, the data revealed that the single most important correlation with the flourishing of a culture was whether pre-nuptial chastity was required or not. It had a very significant effect either way.
Highest flourishing of culture: The most powerful combination was pre-nuptial chastity coupled with “absolute monogamy”. Rationalist cultures that retained this combination for at least three generations exceeded all other cultures in every area, including literature, art, science, furniture, architecture, engineering, and agriculture. Only three out of the eighty-six cultures studied ever attained this level.
Effect of abandoning prenuptial chastity: When strict prenuptial chastity was no longer the norm, absolute monogamy, deism, and rational thinking also disappeared within three generations.
Total sexual freedom: If total sexual freedom was embraced by a culture, that culture collapsed within three generations to the lowest state of flourishing — which Unwin describes as “inert” and at a “dead level of conception” and is characterized by people who have little interest in much else other than their own wants and needs. At this level, the culture is usually conquered or taken over by another culture with greater social energy.
Time lag: If there is a change in sexual constraints, either increased or decreased restraints, the full effect of that change is not realized until the third generation.
Unwin’s observations suggest to me that a socio-biological theory to account for the origins of marriage in all cultures might be possible, as well as an explanation for the fact that marriage is almost universally heterosexual.