Analysis of DNA uncovers a rough dating scene after the advent of agriculture

One other hypothesis I can think of is the advent of barbarian warfare. Many parts of the old testament details how brutal life was, where various tribes are constantly at war and conquering other tribes.

Even several generations of warfare, where each village sacked involved killing the men and abducting the women, would filter out y-chromosomes to see such a large disparity.

Not necessarily. There are a lot of things that the article left out. Number 1 is that the Y chromosome is about 25% of the size of the X chromosomes and is also the fastest evolving portion of the human genome. Since this was a DNA based study, you have to control for this as well. I assume they have, but I don't know for certain. Additionally, aneuploidy (XXY, YYX, etc) may also account for some differences along with chimeric (2+ genomes per person due to fraternal twin merging in womb) anomalies. You also have to control for outliers such as Ghengis Khan and those types of mass rape and pillaging, as he has skewed the statistics a fair bit.

Still, if they controlled for all this, it is an AMAZING finding. That only 6% of males will reproduce is fantastical, especially within an agrarian society. I would love to know of other mammalian species that have such low reproductive rates compared to females.

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

All of these seem possible, to some extant for humans. First, war kills males. A lot of war could potentially kill the majority of males.

Second, infanticide exists within the historical record. SO does slavery, castration, polygamy etc. It doesn't seem far fetched to imagine a highly polygamous society where the majority of men are denied partners by one or more of these.

Re the regions, Figure S4A in the supplemental material (1) suggests that patterns varied somewhat with geography.

1: http://genome.cshlp.org/content/suppl/2015/02/18/gr.186684.1...

You saw this coming? Just how old are you?

This is a great passage from the Red Queen, that might explain what was happening at the time:

In the ancient empire of the Incas, sex was a heavily regulated industry. The sun-king Atahualpa kept fifteen hundred women in each of many “houses of virgins” throughout his kingdom. They were selected for their beauty and were rarely chosen after the age of eight—to ensure their virginity. But they did not all remain virgins for long: They were the emperor’s concubines. Beneath him, each rank of society afforded a harem of a particular legal size. Great lords had harems of more than seven hundred women. “Principal persons” were allowed fifty women; leaders of vassal nations, thirty; heads of provinces of 100,000 people, twenty; leaders of 1,000 people, fifteen; administrators of 500 people, twelve; governors of 100 people, eight; petty chiefs over 50 men, seven; chiefs of 10 men, five; chiefs of 5 men, three. That left precious few for the average male Indian whose enforced near-celibacy must have driven him to desperate acts, a fact attested to by the severity of the penalties that followed any cuckolding of his seniors. If a man violated one of Atahualpa’s women, he, his wife, his children, his relatives, his servants, his fellow villagers, and all his lamas would be put to death, the village would be destroyed, and the site strewn with stones. As a result, Atahualpa and his nobles had, shall we say, a majority holding in the paternity of the next generation. They systematically dispossessed less privileged men of their genetic share of posterity. Many of the Inca people were the children of powerful men. In the kingdom of Dahomey in West Africa, all women were at the pleasure of the king. Thousands of them were kept in the royal harem for his use, and the remainder he suffered to “marry” the more favored of his subjects. The result was that Dahomean kings were very fecund, while ordinary Dahomean men were often celibate and barren. In the city of Abomey, according to one nineteenth-century visitor, “it would be difficult to find Dahomeans who were not descended from royalty.” The connection between sex and power is a long one.

Bryan Sykes has written a series of popular science books about these kinds of genetic discoveries. Very interesting.

Very good. That's probably an important factor.

We are a very social species, the culture we create is our natural environment.

What you're saying isn't wrong, but I doubt that societies where rulers have a monopoly on violence have existed long enough to have had an impact on evolution.

There will be always a few at the top, hierarchies among humans will always exist due to natural differences.

Yea, I'm beginning to think the only real privilege is being born to a powerful and wealthy family.

First: The fight _is_ against the top. 'The top', more precisely the structure that enables 'the top', is the patriarchy that feminist have always been fighting against.

Second: Even thinking of it as 'the top', 'the few that get to have all the pro-creation' as another commenter wrote is bad. Because the 1700 concubines, they weren't treated fairly. They taken away from their parents at age 8, held captive for sex and raped if they didn't comply.

Feminists are fighting for the women first. But the structure that enables this hurts everybody.

You're... not right.

More like out of 5 men, on average only one would have any descendent whose genetic line survived until today. But he would have a lot.

Now, some of the other 4 might have had children, but they might have dies young, or in turn not have had any descendants whose genetic line is still around.

Of course, the same would have happened to women, so maybe out of 15 men and 15 women, 5 women and 1 man have genes that are still around.

Also note that, unless I misunderstand, this only applies to single gendered lineage. That is there must be an unbroken chain of male ancestors for the male genes, and female ancestors for the female genes. If one of the men without surviving male genes had 3 daughters who went on to have lots of kids, his genes wouldn't be seen in this data, even though his other genes are with us.

Having gone through that line of thought, I wonder if we're looking at some kind of "compound interest" effect here. I mean, if the male-only gene has 10% less chance to survive a generation, does it add up to much bigger and bigger numbers after hundreds of generations?

I'm not sure if that clarified much...

Yeah, it isn't clear what timescale they are discussing, but the graphic suggests that a near 1/1 pairing is a very recent phenomenon.

4 or 5 might be high, but it's still noticeable anecdotally (although more rigorous analysis would be interesting).

My ex-wife and I have no children, but her current fiancee has children with his ex-wife (who has no other children), and she and him plan to have children together. My dad has children with his ex-wife (who has no children with other men) and current wife, but my mom (his current wife) has no children with her ex-husband.

So in a very small anecdotal sample, men who have children may often have children with 2 (or more, presumably) women over a lifetime, even though at any given time, monogamy prevails.

Upon Googling, I think this comes from genetic analysis which suggests that people alive today have 4-5x as many female ancestors as male.

I don't know if this statistic is actually limited by "recent history" or not.

> Same for males there's always that 1 mega hotie you want to meet. > The only difference is even average females can have any guy they want while the same doesn't apply to guys.

I'd rather say that the major difference is that while there is no (or very little) opportunity cost for a male that mates with the top woman and the next 100 women as well, there is a big opportunity cost for a female regardless of which male she chooses, so she is much more motivated to choose the top male.

Right. This is not a new theory. It's well known that evolution tends to favor polygamy where females are more selective and males are more promiscuous.

What's interesting is that this apparently started after agriculture rather than before. I had previously thought that maybe hunter gatherers practiced polygamy but it faded away as we become more agricultural.

Also 17 females to 1 male is pretty absurd. Even if you look at cultures that practiced polygamy in recent history it wasn't to that extent. And even when it was practiced, it wasn't necessarily common except in the very upper class, so the average female to male ratio would have been more reasonable.

We can only speculate to what degree this might have shaped our (recent) evolution. That's a huge selective pressure on males to have traits that would lead to them being the local king or whatever they were. And everyone alive today would be descended from those people.

http://blogs.discovermagazine.com/gnxp/2010/08/1-in-200-men-... :

> ~10% of the men who reside within the borders of the Mongol Empire as it was at the death of Genghis Khan may carry his Y chromosome, and so ~0.5% of men in the world, about 16 million individuals alive today, do so. Since 2003 there have been other cases of “super-Y” lineages. For example the Manchu lineage and the Uí Néill lineage. The existence of these Y chromosomal lineages, which have burst upon the genetic landscape like explosive stars sweeping aside all other variation before them, indicates a periodic it “winner-take-all” dynamic in human genetics more reminiscent of hyper-polygynous mammals such as elephant seals. As we do not exhibit the sexual dimorphism which is the norm in such organisms, it goes to show the plasticity of outcome due to the flexibility of human cultural forms.

I have a hunch that this ancient way of warfare is still the optimal way to destroy a culture and achieve total victory. Not that it's acceptable in any way, but imagine if the US had done this in Iraq and Afghanistan. It is heart-wrenching to think about, but I think it would have worked.

And don't forget the death of women during childbirth. That would leave a father/child pair - I'm sure the fathers in that instance would not be voluntarily celibate afterwards.

Here: http://genome.cshlp.org/content/early/2015/03/13/gr.186684.1...

What do Adam and Eve refer to in this context? Also, what do you mean by "more recent"?

What do you mean by that?

I would say if Carlos Bustamante or Stephen Montgomery are ever giving a talk to the public to check them out. They're both based out of Stanford Med, but their research touches on tracing Human demographic history. If she's still interested when applying for colleges, Harvard and The University of Chicago should both be on her list.