Y losses in human history

 The loss of Y chromosomes in our history is a fact. Some researchers put evidence that it is the result of violent deaths at a young age, mainly by wars. Others argue that it could instead be explained by a change in family structures. What is the strength of the evidence? I put evidence about societal changes in a table, with those backings and those against.

Hypothesis	Supporting Evidence	Contrary Evidence
Violent Deaths (Wars)
1. Genetic Bottleneck	Researchers have found evidence of a "genetic bottleneck" roughly 5,000 to 7,000 years ago, where a dramatic reduction in Y-chromosome diversity occurred. This coincides with the rise of organized warfare in early societies .	Counterargument suggests this bottleneck did not affect female genetic diversity, which questions the role of war alone. Female population data doesn't show similar constrictions .
2. Historical Warfare Patterns	Some anthropological studies highlight that early societies often fought over resources, and this could lead to young men disproportionately dying in these conflicts .	Wars tend to impact populations as a whole, including women and children. Additionally, some regions with high Y-chromosome loss did not have extensive war records during the same period .
Family and Societal Structures
1. Polygynous Societies	Anthropological and genetic data support that many early human societies were polygynous, with a few men fathering most children. This could result in the loss of Y chromosomes over generations, as only certain male lines were able to reproduce .	Counterargument from egalitarian societies: Not all early societies were highly polygynous, and in more egalitarian structures, reproductive opportunities were more evenly spread among men.
2. Inheritance Systems	Certain patrilineal inheritance systems, where wealth and status were passed down through male descendants, likely favored particular male lines, marginalizing others .	Some historical societies also practiced matrilineal inheritance or more fluid inheritance systems, which would mitigate the effect of excluding certain male lines .
3. Population Growth and Expansion	Changes in societal structures such as agriculture, sedentism, and wealth accumulation might have led to some men monopolizing reproductive opportunities, reducing Y-chromosome diversity .	The rise of these structures coincided with larger, more stable populations, which may have led to more diversified reproduction across male groups, balancing out Y-chromosome representation.

The polygynous societal structure and inheritance-based concentration of wealth and reproductive rights appear to be the more consistent explanations across multiple sources.

La structure sociétale polygame et la concentration des richesses et des droits reproductifs fondée sur l'héritage semblent être les explications les plus cohérentes d'une source à l'autre.