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

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

#31

Post by MichaelGG »

Houshalter wrote: post #11
Fuxy wrote: post #2

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…

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…

>lead to them being the local king or whatever they were

Or lead them to "steal" secret reproductions? There's only "one" king, but there could be more than 1 "illegitimate" fathers.

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

#32

Post by dragonwriter »

Houshalter wrote: post #11
Fuxy wrote: post #2

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…

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…

> What's interesting is that this apparently started after agriculture rather than before.

Well, the effects become much more pronounced after agriculture.

> 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.

17:1 ratio in females vs. males having descendant lines surviving to appear in modern DNA doesn't imply 17:1 female:male polygyny.

Heck, the reverse (women having multiple partners, especially a higher-station one with better prospects for having offspring and having them succeed in youth and a lower-station one with worse prospects later, perhaps after the previous one died) could contribute to this, though polygyny is probably part of the explanation.

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

#33

Post by CreRecombinase »

andyl wrote: post #17

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.

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

#34

Post by saalweachter »

swagasaurus-rex wrote: post #21
sloreti wrote: post #18

"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.

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.

You still get at least an element of this with pretty recent til-death-do-us-part versions of serial monogamy: Gauss, for instance, had two wives, marrying a friend of his first wife after she died, and had children with both of them.

(I'd be surprised if serial monogamy alone were enough to get a 4:1 ratio, but you can definitely get > 1:1 ratios out of it.)

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

#35

Post by tjradcliffe »

netcan wrote: post #29
swagasaurus-rex wrote: post #15

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 exp…

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.

War has rarely had a significant effect on populations, certainly nothing like the effect of disease. Although many men in the ancient world died by violence (as they do in pre-political societies and failed states today) killing with stone tools is pretty difficult and dangerous, so constant warfare that killed enough men to account for a 17:1 reproductive ratio for long enough to leave its mark today would have made agriculture almost impossible. So it isn't all that likely.

Social constraints on reproduction are considerably more likely. All human societies are mildly polygynous, with high-status males having more mates and low-status males having fewer. This is why human males are somewhat bigger than human females: bigger men were more successful in mate competition, despite the obvious disadvantage of a larger size for a tool-using opportunistic hunter-gatherer-scavenger [].

The remarkable thing about this finding is that the level of social control was high enough to sustain such an effective* exclusion of most men from mating opportunities. In every modern human society cheating ("extra-pair copulations") is a significant factor in reproductive statistics, and a 17:1 ratio suggests a system that was capable of actually excluding, not just nominally excluding, the vast majority of men from reproducing.

It's difficult to see how that could happen in a modern human population, but then again: men and women today are descendents of the 5% of males who were successful in reproducing under those circumstances, so it's not entirely implausible that we are considerably fiercer mate competitors than our pre-agrarian ancestors.

[*] Bigger, more muscular bodies require more fuel, so bigger men starve to death more frequently than smaller men during bad years, which all the data we have on pre-political peoples suggest were not infrequent.

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

#36

Post by dragonwriter »

tjradcliffe wrote: post #35
netcan wrote: post #29

Earlier quoted context omitted.

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.

War has rarely had a significant effect on populations, certainly nothing like the effect of disease. Although many men in the ancient world died by violence (as they do in pre-political societies and failed states today) killing with stone tools is pretty difficult and dangerous, so constant warfare that killed enough men to account for a 17:1 reproductive ratio for long enough to leave its mark today would have mad…

> and a 17:1 ratio suggests a system that was capable of actually excluding, not just nominally excluding, the vast majority of men from reproducing.

It doesn't actually imply that, because many of them could have reproduced, but not had offspring that survived to reproduce for sufficient numbers of generations. Modern DNA won't distinguish that from didn't reproduce. So, the fact that the vast majority of men of the time weren't successful in reproducing in the long term (viewed by having descendants survive to the modern day) doesn't mean that they were effectively excluded from reproduction.

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

#37

Post by brazzy »

Balgair wrote: post #26
swagasaurus-rex wrote: post #15

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 exp…

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 w…

> I would love to know of other mammalian species that have such low reproductive rates compared to females.

Some species of deer probably match it.

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

#38

Post by tjradcliffe »

Balgair wrote: post #26
swagasaurus-rex wrote: post #15

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 exp…

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 w…

None of the things you mention are large enough to account for more than a tiny fraction of this observation. There are only a handful of cases like Ghengis Khan and that Irish king who are ancestors to a fraction of a percent of the human population, which in any case don't exclude other men from ancestry. If you have ten children and I have one, I am still an ancestor, although your DNA will show up more frequently in future generations than mine.

These results suggest the actual exclusion of 95% of the male population from reproduction. Chromosomal disorders affect less than 1% of the population, which would be deep in the noise in this study.

With regard to the rate of evolution on the Y chromosome, I think it's pretty plausible that people who do this stuff for a living are aware of it and corrected for it. We don't know that for certain, but since we don't know anything with certainty--only with an overwhelmingly high degree of plausibility--that isn't a big criticism.

Edit: also, any harem-keeping species is likely to have a high proportion of genetic losers amongst the males: https://en.wikipedia.org/wiki/Harem_%28zoology%29#Mammals

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

#39

Post by phkahler »

ccvannorman wrote: post #16

"somehow, only a few men accumulated lots of wealth and power, leaving nothing for others" Yeah, thank god we're past this as a species

I thought it had been observed with monkeys or apes that in times of scarcity they will share, but if you dump a whole truck load of bananas they will fight over them. The rise of agriculture would be a similar time of plenty which may be what triggered all the fighting and hoarding.

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

#40

Post by Balgair »

brazzy wrote: post #37
Balgair wrote: post #26

Earlier quoted context omitted.

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 w…

> I would love to know of other mammalian species that have such low reproductive rates compared to females. Some species of deer probably match it.

True! Then it seems that the early agrarian humans had more of a herd mentality or reproductive structure of winner take all. Do other apes or monkeys have similar breeding structures? Fascinating stuff.
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