[dubhrosa]

Why is the war hypothesis considered more likely than say a widespread, long lived contagious disease that had significantly higher mortality in males than females? If there was a period of widespread warfare for sustained periods, it's hard to see how "clans" would continue to engage in warfare beyond say 50% loss of the fighting forces. Wouldn't some women have joined the clan fighting forces also if it was an existential struggle? Why wouldn't clans have submitted to their conquerors and joined forces against common enemies - which was the pattern in many historical accounts of widespread warfare.

[DamnYuppie]

Well to be honest I believe you underestimate humanity. There are way too many instances of clans who would fight till nearly both parties were eradicated. Regardless of that I am not convinced that is the root cause.

I feel this whole theory misses some key elements of our ancestors. First the idea that each male was able to reproduce at the same rate or had the same opportunity to breed as each other; this is not how nature really works! For most mammals only a few males get to bread each year with ALL the females in a herd. The alpha male will do the overwhelming majority of the breading for X number of years until displaced, i.e. dies of natural causes or is violently displaced. Our ancestors were most likely not very different. This, in my opinion, could be one of the reasons women in a group will synchronize their menstrual cycles, as it would help to ensure the male could bread everyone in a short time period and not worry about competitors sneaking in as much.

Also the idea that there were equal number of men and women needs to be looked at. Again, in nature, there is generally way more females then males. A healthy and diverse herd is considered to be around 70% female and 30% male.

[paidleaf]

> I feel this whole theory misses some key elements of our ancestors. First the idea that each male was able to reproduce at the same rate or had the same opportunity to breed as each other;

The article is talking about Y chromosomes, not the rate of successful breeding of each male. In patrilineal clans, all males share the same Y chromosome since they are all related. It doesn't matter which males within the clan breed when you are analyzing Y chromosomes.

As long as a single male within the clan breeds, the Y chromosome will be passed on.

The question is why many Y chromosomes disappeared from the gene pool. Why the diversity in Y chromosomes declined so drastically.

> The alpha male will do the overwhelming majority of the breading for X number of years until displaced, i.e. dies of natural causes or is violently displaced.

Once again, that doesn't matter in Y chromosomal diversity analysis. It doesn't matter whether you or your brother was "alpha". It doesn't matter which one of you fathered most of the descendents since both you and your brother carry the same Y chromosome.

The question is, if you were living thousands of years ago, why you, your brother, your paternal related male cousins, etc didn't breed. IE, why your clan's Y chromosomal legacy didn't make it while your mother, sister, female cousin's, etc mDNA ( mitochondrial DNA ) did make it. Why did your female genetic legacy make it while your male genetic legacy did not?

It's pretty clear that warfare played a role. There is no disease that wipes out only the males and none that wipes out 100% of the male population. Even if disease wiped out 99% of the males in your clan, the 1% remaining can breed with all the females and replenish the clan and your Y chromosome would live on.

[philipodonnell]

You're giving way too much credit to what a war looked like >5K years ago. There were no "fighting forces", there was just however many men there were, maybe 20-30 in a clan. IIRC from people studying tribes before western civilization arrived, clan warfare was pretty much about getting 2-3 neighboring clans to temporarily gang up another clan's village, kill all the males + women who resist or sell them into slavery, raze the village and then split the remaining women up amongst the victors. Rinse and repeat amongst the victors themselves and it's just not that much of a stretch to eliminate 50% of the men from an area.

[newest_user_]

I haven't read the original article to see if they address your question -- but generally a trained expert can tell if a disease ravaged someone by markers left of their skeletal system (increased iron deposits, lack of calcium, etc.)

Knowing that, if we wanted to test the hypothesis that it was a disease then we would expect to see those markers on either a majority of males or we would see an equal distribution with the male skeletons trending younger then female ones. After the disease passed (like black death did) we would see male average life spans increase and a decrease in the disease markers.

[hashkb]

Well, there are more wars than plagues in recorded history. Also, I'm not familiar with many male-only plagues.

[paidleaf]

> Why is the war hypothesis considered more likely than say a widespread, long lived contagious disease that had significantly higher mortality in males than females?

Most likely because disease don't discriminate along clan lines and even if disease killed a portion of a clan's males, the other males of the clans can just breed with females and the relative diversity of the male clan line is still maintained. Also, the fact that it has occurred throughout the world indicates it wasn't disease but the structure of the clan and the warfare.

> If there was a period of widespread warfare for sustained periods, it's hard to see how "clans" would continue to engage in warfare beyond say 50% loss of the fighting forces.

Why do say that? Also, you are assuming that one clan won't have an advantage over the other clan and that one side won't be victorious.

> Wouldn't some women have joined the clan fighting forces also if it was an existential struggle?

No because it wasn't an existential struggle for women. It was an existential struggle for men. Women can breed with the conquering males. Perhaps a small number of women may fight but they'll be killed or subdued very quickly. Males are much stronger than females on average.

> - which was the pattern in many historical accounts of widespread warfare.

And the pattern is that males conquer and take the women, land, resources, etc.

If you want to see how conquerors genes spread. Look at mexico's mestizo genetics.

"A 2012 study published by the Journal of Human Genetics Y chromosomes found the deep paternal ancestry of the Mexican mestizo population to be predominately European (64.9%), followed by Amerindian (30.8%) and Asian (1.2%)"

"Also a study published in 2011 on Mexican Mitochondrial DNA found that maternal ancestry was predominately Native American (85-90%), with a minority having European (5–7%) or African (3–5%) mtDNA."

https://en.wikipedia.org/wiki/Mestizos_in_Mexico

Amongst mixed race mexicans, 65% are descended from european males and 85-90% are descended from native females. And the european males didn't kill off all the native males in mexico. The european males, as conquerors, seized the most land, resources and power for themselves and their male offsprings. This gives an enormous breeding advantage that in just a couple of hundred years, native mexican male genetics is a distinct minority while the native mexican female genetics is a distinct advantage.

Keep in mind that at no time in mexican history were full-blooded european males a significant portion of the population. It's just the power of mathematics ( exponential growth ).

Think about it, if you have 10 kids and your kids have 10 kids and their kids have 10 kids, it adds up really quickly.