I've suspected as much would happen during the agricultural revolution, but I did not expect such a huge disparity.
If the 51% male/female ratio did not change, then 16 out of 17 males must have either been killed, enslaved, or been left frustrated. This would imply a highly patriarchal society where the local king and his cronies are the only ones fed, and to whom you would sell your daughters to. The only other explanation would be mass infanticide of males, but to see this in multiple regions is suspect.
"It wasn't like there was a mass death of males. They were there, so what were they doing?" The article raises a very good question. In all places studied, agriculture must have favored a highly stratified society.
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.
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.
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.
Since a lot of early civilizations seemed to be very slave heavy I wonder if that had anything to do with it. Agriculture requires more labour which leads to more slaving. Male slaves would work the fields with less of a chance for reproduction, and the landowners/slaveowners would have their pick of the female slaves.
Just started reading Harari's brief history of humankind and this gem perfectly fits in the rather unsettling story of our genetic pool. It is no longer the natural environment setting the conditions for who's fit to survive/chosen for reproduction but the present human culture which in turn is just the result of the previous.
If I had to choose an algorithm as an analogy, I'd say it is a recursion waiting for stack overflow. :)
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.
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.
"In more recent history, as a global average, about four or five women reproduced for every one man"
Correct me if I'm wrong, but isn't this the same as saying one man, on average, will father a child with about four or five different women? I suppose given the timescale being discussed, "recent history" may mean the last few centuries, but this average still sounds very high to me.
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?
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.
Makes perfect sense to me. If you look at our culture now there is always that one male all the females in a group tend to go for.
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.
The advent of agriculture gave females the ability to support their children more easily without the help of males and the more desirable males could have more offspring with so much food available.
Basically less females had to settle for second best to have offspring.
> 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.
This is not my research area. However, I can't help but the results seem to radical to me. The dip in male diversity seems far too synchronized among so many different regions / cultures. Are there examples in recorded history of sudden reductions in male diversity that lasted for multiple generations?
> ~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.
> Another member of the research team, a biological anthropologist, hypothesizes that somehow, only a few men accumulated lots of wealth and power, leaving nothing for others.
This line cracked me up.
Yes, "somehow" indeed. Quite a mystery we have on our hands here!
Not particularly surprising. In the ancient world, men were often killed in various ways (conflict, hunting accidents) or enslaved so the gender ratio was quite skewed.
I mean, typical ancient warfare meant you attack a town, kill/enslave all the men and boys, rape all the women, and ensure your culture's dominance over them for the next generation or two...
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.
Sounds to me like slavery. The women slaves had babies, the male slaves were workers and soldiers.
In a way, it sort of sounds like a eusocial sort of society, like a bee colony (but with the male female roles reversed). One reproducing male, many reproducing females, many non-reproducing males.
I found the original article but sadly not freely available. This psmag.com article is thin and the graph of the data is so small I can't read much off of it. Google couldn't find any larger versions of the graph.
In populations studies at all scales, Adam is more recent than Eve. 10 years ago, I read it was Eve 120,000 years ago and Adam 60,000 years ago for the out of Africa theory.
- Claimants go to war with one another. Soldiers are invented, voluntary and noble at first. Religious later. Can't do mass conscription from the common man as he's working the essential farms.
- Losers happen. Slavery is invented.
- Slaves work the mines and other harsh labor, which allows for post-agrarian activities and advanced economies.
- King sits back and lets the the whole clusterfuck evolve in his favor.
A auto-catalytic male shortage. Easy peasy.
Inadvertently, I have just Twitterized the Old Testament.
My 16 yr old is interested in pursuing this field (not sure what to call it - 'Genetic Anthropology'?). Can anyone recommend online resources to help a newbie get the lay of the land? Or in-person resources (talks, exhibits, clubs etc.) near Palo Alto CA ??
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.
You should email Razib Khan at UC Davis. He's been blogging about this stuff for years. And just earlier today, the NYT announced that he's been brought on as one of their new opinion writers.
Eunuch's and harems. The rich and powerful males kept all their local women in a harem and forced all the other competing males to become eunuchs. Not fun, but it fits with the Monty Python version of history.... ;)
[+] [-] swagasaurus-rex|11 years ago|reply
If the 51% male/female ratio did not change, then 16 out of 17 males must have either been killed, enslaved, or been left frustrated. This would imply a highly patriarchal society where the local king and his cronies are the only ones fed, and to whom you would sell your daughters to. The only other explanation would be mass infanticide of males, but to see this in multiple regions is suspect.
"It wasn't like there was a mass death of males. They were there, so what were they doing?" The article raises a very good question. In all places studied, agriculture must have favored a highly stratified society.
[+] [-] swagasaurus-rex|11 years ago|reply
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.
[+] [-] Balgair|11 years ago|reply
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
[+] [-] netcan|11 years ago|reply
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.
[+] [-] bluenose69|11 years ago|reply
1: http://genome.cshlp.org/content/suppl/2015/02/18/gr.186684.1...
[+] [-] glibgil|11 years ago|reply
[+] [-] JeffL|11 years ago|reply
http://amazon.com/Red-Queen-Evolution-Human-Nature/dp/006055...
[+] [-] ardit33|11 years ago|reply
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.
[+] [-] peter303|11 years ago|reply
[+] [-] seokranik|11 years ago|reply
[+] [-] tormeh|11 years ago|reply
[+] [-] noiv|11 years ago|reply
If I had to choose an algorithm as an analogy, I'd say it is a recursion waiting for stack overflow. :)
[+] [-] asdkl234890|11 years ago|reply
[+] [-] Padding|11 years ago|reply
[+] [-] littletimmy|11 years ago|reply
Feminists, take note: men are not privileged. Just those who were privileged were men. The fight must be against the few at the top.
[+] [-] victorhn|11 years ago|reply
[+] [-] MollyR|11 years ago|reply
[+] [-] rockmeamedee|11 years ago|reply
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.
[+] [-] sloreti|11 years ago|reply
Correct me if I'm wrong, but isn't this the same as saying one man, on average, will father a child with about four or five different women? I suppose given the timescale being discussed, "recent history" may mean the last few centuries, but this average still sounds very high to me.
[+] [-] BurningFrog|11 years ago|reply
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...
[+] [-] swagasaurus-rex|11 years ago|reply
[+] [-] steven777400|11 years ago|reply
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.
[+] [-] clay_to_n|11 years ago|reply
I don't know if this statistic is actually limited by "recent history" or not.
[+] [-] Fuxy|11 years ago|reply
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.
The advent of agriculture gave females the ability to support their children more easily without the help of males and the more desirable males could have more offspring with so much food available.
Basically less females had to settle for second best to have offspring.
[+] [-] tomp|11 years ago|reply
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.
[+] [-] Houshalter|11 years ago|reply
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.
[+] [-] rhema|11 years ago|reply
[+] [-] dalke|11 years ago|reply
> ~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.
[+] [-] deciplex|11 years ago|reply
This line cracked me up.
Yes, "somehow" indeed. Quite a mystery we have on our hands here!
[+] [-] Mikeb85|11 years ago|reply
I mean, typical ancient warfare meant you attack a town, kill/enslave all the men and boys, rape all the women, and ensure your culture's dominance over them for the next generation or two...
[+] [-] tormeh|11 years ago|reply
[+] [-] snickerdoodles|11 years ago|reply
[+] [-] robbrown451|11 years ago|reply
In a way, it sort of sounds like a eusocial sort of society, like a bee colony (but with the male female roles reversed). One reproducing male, many reproducing females, many non-reproducing males.
[+] [-] jrells|11 years ago|reply
Does anyone know a better source?
I found the original article but sadly not freely available. This psmag.com article is thin and the graph of the data is so small I can't read much off of it. Google couldn't find any larger versions of the graph.
[+] [-] josu|11 years ago|reply
[+] [-] stillsut|11 years ago|reply
[+] [-] evv|11 years ago|reply
[+] [-] ll123|11 years ago|reply
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[+] [-] unknown|11 years ago|reply
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[+] [-] AhrowTway|11 years ago|reply
- No contraception. Much baby.
- Many claims to throne in 14-18 years.
- Claimants go to war with one another. Soldiers are invented, voluntary and noble at first. Religious later. Can't do mass conscription from the common man as he's working the essential farms.
- Losers happen. Slavery is invented.
- Slaves work the mines and other harsh labor, which allows for post-agrarian activities and advanced economies.
- King sits back and lets the the whole clusterfuck evolve in his favor.
A auto-catalytic male shortage. Easy peasy.
Inadvertently, I have just Twitterized the Old Testament.
[+] [-] andyl|11 years ago|reply
[+] [-] CreRecombinase|11 years ago|reply
[+] [-] clarkm|11 years ago|reply
[+] [-] bengrunfeld|11 years ago|reply