From Wikipedia:
The Neolithic Y-chromosome bottleneck refers to a period around 5000 BC where the diversity in the male y-chromosome dropped precipitously across Africa, Europe and Asia, to a level equivalent to reproduction occurring with a ratio between men and women of 1:17. Discovered in 2015, the research suggests that the reason for the bottleneck may not be a reduction in the number of males, but a drastic decrease in the percentage of males with reproductive success in Neolithic agropastoralist cultures, compared to the previous hunter gatherers.
The development of farming and then animal herding greatly increased the number of humans — which continued to have evolutionary consequences for our species — and created productive assets (farms and animal herds) worth fighting over. Successful male teams (typically organised as clans) wiped out unsuccessful male teams and took their women as spoils.
Hence, there is a dramatic bottleneck in male lineages but not in female lineages. This pattern stopped with the development of chiefdoms and especially states, though not so much on the Steppes, whose states were more like super-chiefdoms and where intense competition over resources (and women) continued.1
This had consequences. A major one is that the male expression of human genes became dramatically better at forming and maintaining teams — as there was drastic selection pressure for that — but the female expression of human genes did not.
This is why young schoolboy sporting teams regularly crush adult women’s national teams in team sports such as soccer. It is not that schoolboys have the strength advantage over women associated with adult men (they are often not particularly advantaged around age 14-15). It’s simply that human males are much more likely to “get” teamwork at a visceral level.
At least some of the differences in the statistical distribution of cognitive traits between men and women comes from this genetic bottleneck’s intense selection pressure differences. This is particularly clear in social patterns. For instance, men readily form hierarchies — often using physical cues such as height to do so.
Men focus on roles, suppressing or otherwise managing their emotions to do so. They regularly test each other — hence ragging each other, making appalling jokes, etc. Such mechanisms generate trust, as they test whether you will fold under pressure, whether one can say outrageous things and still get support. Hence the popular quip:
Men insult each other but they don’t mean it. Women compliment each other but they also don’t mean it.
Men roast each other as tests because so much male interaction is about teamwork, and the roles and reliability that requires, while women typically look to emotional connection. Given that the latter requires a lot of interaction to build up trust, yes, female friendships can be quite intense, but relations between human females can also be viciously unstable and fissile.
These differences have other social consequences. Men are notably more positive about free speech than women, because men often see speech as a test while women are more likely to see it as a threat. As universities have feminised, the male-female differences on free speech among students have become more pronounced. Men are systematically more tolerant of alternative points of view than are women.
Orwell’s famous comment in his novel 1984:
It was always the women, and above all the young ones, who were the most bigoted adherents of the Party, the swallowers of slogans, the amateur spies and nosers-out of unorthodoxy.
Was a great novelist doing what great novelists do: noticing.
As part of the teamwork focus, men tend to be the social solidarity sex while women are not. Women are much less likely to have friends of lower socio-economic status than are men. For women, such friends are much less likely to be worth the emotional investment. For men, they may be useful members of a future team.
As institutions, occupations and public discourse become more feminised, there has been a shift in patterns of language. A massive study of patterns of language use found a dramatic shift since the 1980s, such that:
our results suggest that over the past decades, there has been a marked shift in public interest from the collective to the individual, and from rationality toward emotion.
All this means that male-dominated institutions and spaces will be generally better, often much better, at generating and managing feedback than female-dominated spaces. When people note that feminising institutions and occupations have a strong tendency to become less functional, it is precisely because they are worse at generating and managing feedback, and at generating and maintaining trust.
- This paper attempts to explain the extreme narrowing of surviving male lineages by the adoption of patrilineal systems and polygyny. While the shift to patrilineal systems in itself does increase unequal lineage success—as does polygyny—much of the point of the shift to patrilineality was precisely that warriors who grow up together are better warrior teams.
Moreover, there is considerable evidence of violence after the shrinkage of male lineages dramatically slowed — and then reversed — with the development of chiefdoms, and especially states. These suppressed violence, but not patrilineality or polygyny. In many societies, polygyny actually intensified with the rise of states.
The bottleneck effects continued to echo down populations. The extraordinary reproductive success of particular male lineages is associated either with pastoralist violence and conquest and/or early state creation. Further, the notion that the majority of male lineages just passively accepted their reproductive exclusion flies in the face of a huge amount of evidence — especially as the examples of very successful pastoral lineages occurred in societies with notoriously high levels of violence, including as raiders, such as across the Steppes and in Ireland.
Moreover, polygyny is associated with higher rates of violence, single-spouse marriage with higher social cohesion. Nor was the creation and maintenance of states typically a peaceful process: periodic violent peaks in Chinese history, for example, were extraordinary. It was precisely the creation of a reproductively-excluded underclass that provided so much of the impetus for the banditry and mass peasant revolts that are such a feature of Chinese history. So, while patrilineality and polygyny were definitely factors in the wildly differentiated success rates of male lineages, considerable levels of violence and contestation over resources and women — that selected in favour of male teamwork — were clearly also very much in play.
