A common trend in the pill communities is to reach about 7,000 years into history to where there was a bottleneck in the Y-Chromosome whereby apparently for every man that was reproducing there were 17 women, to try to demonstrate the excessive extent of women's hypergamous nature and the extent of sexual inequality that results from a society without enforced monogamy. Of course the natural reaction to this is that it's ridiculous on its surface and there's no way such a set up would be sustainable, let alone for the 1,500-2,000 years in which this bottleneck persisted, and I would argue that this reaction is justified. The article that is often cited includes an overzealous headline claiming that only 1 in 17 men reproduced 7,000 years ago, but the study that it's based on didn't prove that at all. All it showed is that in that time period a lot more mitochondrial lineages were represented than Y-Chromosomal ones.

Researchers at Stanford University have came up with a model wherein as hunter gatherer tribes started becoming agriculturalists they would organize along patrilineal lines, concentrating male lineages whereas before they'd be more spread out. This would mean that when violent intertribal conflict would occur and a tribe would be wiped out, Y-chromosomal diversity would suffer as a patrilineal lineage would be wiped out with them. Women however would more frequently move between tribes, spreading out their mitochondrial DNA and allowing it to be retained when its carriers were also killed, or of course when the women of a defeated tribe would be raped or taken as concubines it could also survive. This effect would allow for a reduction of Y-Chromosomal diversity without an equivalent reduction in the male population and without equivalent rates of polygamy. They confirmed this effect could account for the bottleneck using computational models.

https://www.nature.com/articles/s41467-018-04375-6

The researchers also made a thread on Reddit where they actually responded to the contention that polygamy was the driving force behind the bottleneck, saying:

We believe that it can't, for the following two reasons: (A) for the ratio effective population sizes among males and females to have stayed around approximately 1:17 across much of the Old World for approximately 1500 years requires an implausible level of polygamy and hereditary inequality. Extreme polygamy, with more than say 3 wives to a man, or highly transmissible differences in reproductive success due to extreme wealth distributions are characteristic of large-scale complex societies or “civilisations”; they are unlikely to be sustained in a small-scale society that we see just after the Neolithic transition to farming and herding. Such small-scale societies still exist in Amazonia and in Papua New Guinea, and until recently in India, Africa, some parts of Southwest China and Southeast Asia, and the Pacific. From ethnography, we know that rates of polygamous marriage in small-scale societies rarely exceed 15%, and usually with at most two wives.

(B) In every part of the Old World, the bottleneck lifts approximately 5000-4000 years ago. This is precisely the period when chiefdoms and states first emerge, often associated with extreme inequality. Mass human sacrifice, for example, is commonly seen in the first states. However the emergence of chiefdoms and states is associated with the lifting of the bottleneck, not its intensification. https://www.reddit.com/r/science/comments/8nrxzy/about_7000_years_ago_something_weird_happened_to/

So until polygamy can be directly proven to be the primary cause of this bottleneck I think this explanation stands as the most realistic.