8,000 Years Ago, 17 Women Reproduced for Every One Man

[AngryAmish]

http://www.psmag.com/nature-and-technology/17-to-1-reproductive-success

"Once upon a time, 4,000 to 8,000 years after humanity invented agriculture, something very strange happened to human reproduction. Across the globe, for every 17 women who were reproducing, passing on genes that are still around today—only one man did the same.

"It wasn't like there was a mass death of males. They were there, so what were they doing?" asks Melissa Wilson Sayres, a computational biologist at Arizona State University, and a member of a group of scientists who uncovered this moment in prehistory by analyzing modern genes."

Very interesting. Maybe Old Europe was not the egalitarian paradise theorized. Or maybe the opposite.

[bklyncowgirl]

1. I can think of several possibilities, war and the development of elite sectors of society are two.

The 17-1 ratio is surprising but this is the period in which humanity for better or for worse began to develop specialization and class structure. It was also a period in which a great deal of fighting must have happened as tribal groups accumulated livestock and land and had to defend it from outsiders--or tried to take what other groups had. A hunter gatherer group can move on to less crowded areas to avoid conflict--agriculturists have a bond to the land and livestock to defend.

War--which in hunter gatherers societies may have been largely ceremonial with elaborate rules of conduct--think the Plains Indians--suddenly got much more deadly.

Who would do most of the fighting--young men of course. They'd also tend to die at higher rates than women who's greatest risk was childbirth. The older men, the survivors, the successful warriors and agriculturists, especially those who had accumulated wealth, would do most of the reproducing--especially if they were stealing and/or raping their neighbors' women.

We do ourselves a disfavor when we romanticize the past. What's remarkable isn't that this happened but that humanity--at least to some extent and in some places and times--rose above this level of existence.

[TreasonousBastard]

2. Harems...

Lions, apes... Wildlife tends to create dominant males who do the mating, so why wouldn't our primitive ancestors have done the same?

[bklyncowgirl]

6. Despite my feminist inclinations I'd tend to agree

We human females have a great disadvantage that other animals don't have--our offspring require long-term care. A woman had a better chance of her children surviving if they were under the protection of one of these dominant males--even if she had to share him with other women. Read your Bible. It's a pretty good account of the lifestyles and mores of a nomadic pastoral people. The Patriarchs all had multiple wives and concubines--some acquired by trade others by conquest.

[edhopper]

11. That was my initial thought as well. nt

[Chathamization]

19. What's the prevalence of animals with dominant males vs. animals who pair off for life?

The impression I get is that most animals tend to mate and move on, but there are some who mate for life and some where a dominant male mates with several females in the group (and, of course, other situations as well).

[TreasonousBastard]

21. Not an expert in sex in the wild, but...

I just know it happens. I suppose we should look at our cousins the apes more than at lions, wolves or rodents. But, even there, while gorillas form troops with dominant males, others, like bonobos, are a bit more loose in their apely morals. Rather like us they are.

[muriel_volestrangler]

29. I don't think it has to be 17-1 over just 1 generation - a lower ratio, but inherited

over several generations would have the same effect.

Consider Man A, who does well - he has 4 children who survive to reproduce themselves, including 2 sons. So that Y chromosome has gone from 1 individual to 2. But men B through F don't do so well - their children don't survive at such a rate, and between those 5 men, they have 8 children, including 4 sons, that survive to have families of their own. The population of men has stayed the same from one generation to another - 6 men - but the 'A to the rest' ratio has changed from 1:5 to 2:4, or changed 2.5 times. If that reproductive advantage is inherited by all the men (and is happening in a large population, so we can handle fractional amounts), then by the next generation it's 6.25, and the next 15.625 - and we've more or less reached that 17:1 ratio in 3 generations.

In practice, such an advantage isn't inherited perfectly by all sons. But if it persists, partially, over a few generations, it could produce what they've found - they wouldn't be able to tell if something happened over 1 generation or 5.

[XemaSab]

31. I had the same thought downthread

It probably wasn't like the FLDS where one man had a huge harem and the next 16 men were SOL.

It could be as simple as putting one family on a nice river valley and another family on a rocky hillslope and seeing where the two families are in 5 generations.

[LeftinOH]

3. Men fought with each other - constantly, and the "winners"

got the women. Just like many other animal species.

[treestar]

13. We aren't things to be got

When we pick a man, believe it or not, we think about it. We aren't animals.

[kelly1mm]

26. 4000-8000 years ago I doubt there was much picking going on. nt

[Telcontar]

28. Club upside the head isnt just for comedic effect

Pretty sure much of the ancient world reproduced by what we call rape today.

[LeftinOH]

33. Early humans were animals - and acted like it; I

should have referred to "males and females" of the species, rather than man & women. We're not talking about modern humans.

[kcr]

34. Not modern culturally. But they were human exactly the same way we are.

No different physically.

[Atman]

4. That was a lucky man.

[panader0]

5. Lucky? I'll bet he was worn to a frazzle.

[Codeine]

18. "The spirit is willing,

but the flesh is bruised and spongy."

[Chathamization]

20. Mel Brooks did a bit on this

1:40 to 3:10.

#t=1m40

[The2ndWheel]

7. Any individual male isn't needed for reproduction

1 can impregnate 30 women in 30 days. That population doubles in a year. 1 women can have 30 babies with 30 men, but it's going to take more than a few decades. The advent of agriculture only made that reality more pronounced.

If I'm reading that graph correctly, there's a spike in the amount of males having children about 5,000 years ago, give or take. That's about when organized religion showed up.

When it comes to reproduction, men just aren't as needed, and are just more desperate. That's why men can do some stupid, wrong, or even bad things for that attention.

[AngryAmish]

8. About 5000 years ago the secondary productions revolution happened

Maybe population rose with pastoralism and more men could find a woman/women to have families with.

[The2ndWheel]

9. I wouldn't doubt it

Anything that helped to bring people together could work. I'm sure they all work together in concert, concentrating not just resources, but people. Bound to figure out some social norms in such conditions.

[bklyncowgirl]

15. You also have the rise of centralized government--and stability especially in places like Egypt.

Being a peasant under the Pharoahs may not have been a bed of roses but at least you were not likely to have your village attacked by strangers from the next town as long as the king was doing his job.

A man could work his assigned plot of land and as long as he worked hard, the gods cooperated and the harvest was good he'd make enough to keep a wife and family fed and clothed. If he was drafted for war he was part of a large army with a medical corps and thus more likely to make it out of there alive than in your basic tribal struggles. Those taxes he had to pay to the king and the local temple must have hurt--not to mention building those pyramids--but state granaries provided food in hard times. Under those circumstances monogamy worked very well as a survival strategy.

In Egypt, even the upper classes (with the exception of the king) were monogamous. Here is the 6th dynasty Vizier Ptahotep's advice on a happy marriage:

When You prosper, found your house,
love your wife with ardor,
fill her belly, clothe her back,
ointment is a remedy for her body.
Gladden her heart as long as You live.
She is a fertile field, useful to her master.
Do not contend with her in a court of justice,
(and) keep her from power, restrain her.
Her eye is her storm when she gazes.
You will make her stay in your house.
If You push her back, see the tears !
Her vagina is one of her forms of action.
What she enforces, is that a canal be made for her.

I think the last bit means "be nice to your wife or she will cut you off from sex!"

[hunter]

10. And every one of us has a few of those men among our ancestors.

That's probably explains why so many men are assholes, including my own fine self.

But I like to imagine it happened this way: All the manly men were off fighting and raping and pillaging but mostly winning themselves Darwin Awards, while a few men stayed home and worked with the women, or ran off into the wilderness when everything turned to shit, and the women in the distant peaceful places thought the exotic looks of these deserters were hot, and greatly appreciated how they brought new skills into the community.

[treestar]

12. Polygamy?

Though it might not have been the most desirable genes. Could have been the strongest men, i.e., including the rapists.

[chowder66]

14. What about homosexuality?

"It wasn't like there was a mass death of males. They were there, so what were they doing?"

[snooper2]

16. holding lots of meetings to figure out how to establish the patriarchy

[chowder66]

22. : ) nt

[NickB79]

25. That's what I was wondering as well

Problems arise when you have large populations of young, virile men with no prospects for sex or raising families. China is starting to see this as their one-child policy, combined with sex-selective abortions of the 90's, plays out: http://www.cnn.com/2012/11/14/opinion/china-challenges-one-child-brooks/

So, what exactly were they doing sexually to stop themselves from going apeshit?

[H2O Man]

17. please

[lumberjack_jeff]

23. It's good to be the tribal chief. n/t

[AngryAmish]

24. kicking for the pm crowd

Life is hell.

[arcane1]

27. I wonder how much it differed in different environments.

[XemaSab]

30. Was it one man for every 17 females, or 1 Y chromosome for every 17 mitochondria?

I could see a situation where a local strongman and his sons just swamped the DNA of a region.

Instead of one man with 17 wives, it's one man with four wives, then his 20 sons are all successful and they all get four wives, then their 400 sons are all successful and they all get four wives who aren't related to any of the preceding wives, and before you know it, all 1,684 women in a 20-mile radius are married into this clan.

Meanwhile, Joe Schmo has 2 daughters with his one wife, but they're both going to be married off into the strongman's clan, and his 2 sons are lucky to get one wife each (probably daughters and granddaughters of the strongman).

Under this scenario, the strongman has 8,000 great-grandsons to carry his Y chromosome, while Joe has 8. None of Joe's descendants are getting killed off or going gay, but he's still not a genetic winner here compared with the strongman. Even if there are 99 other Joes out there, their combined male line is going to be 1/10 the size of the strongman's.

This is an extreme scenario, of course, but even small differences in reproduction and survivorship add up over the generations.

[joshcryer]

32. I found a good blog on it:

Has a good info-graphic but I don't want to inline it because it's huge: http://mathbionerd.blogspot.com/2015/03/a-recent-bottleneck-of-y-chromosome.html

The study is here but I don't have access to it: http://genome.cshlp.org/content/early/2015/03/13/gr.186684.114.abstract

My guess it's probably a mix of what you suggest and warlordism in general. In reality, the population of men having children probably didn't decline, but rather, their ancestors didn't get to make it (no protection, war, famine, whatever, killed off the poor folk).

The key term the authors use is "effective population," ie, the population whose ancestors made it. And it seems that something dramatic happened with the advent of agriculture (and city states, I'd guess).