7 ms·

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

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.

swagasaurus-rex 12y ago
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.
- bilbo0s 12y ago
  This is the actual explanation. With one caveat... slavery. Basically, agriculture allowed people to specialize. This included specializing in killing. (Soldiers). You would use these specialists to conquer other lands. Which, in turn, provided slave labor to increase production in agriculture and other sectors. So the conquered females would be used as "rewards" for the conquerors. And the conquered males would be used to increase production across the conquering society via slave labor. So the explanation is pretty simple. In fact, the 17 to 1 figure is so low that I question whether they aren't missing something ??? Societies that developed later generally required enormous amounts of slave labor. That, coupled with the fact that there would have been an enormous amount of killing involved in taking the slaves in the first place, makes me wonder how the numbers turned out so evenhanded? I would have expected it to be an order of magnitude higher. But they did the study and have the data... so life must not have been quite as brutal as I thought it was. I suppose it is possible that life was brutal... and less desirable females simply may not have been taken? This happened a lot in our own history. Slave auction records show that some female slaves in America sold for as much as 100 times the rate of a "regular" female slave. (And even more in some private trades we have records for). We can speculate on why that may have been... but I think it's safe to assume that in a less sophisticated time they may have simply dispensed with females and males who were in some way undesirable, or were not likely to survive the journey back.
  - Perceval 12y ago
    Sparta maintained a 10:1 ratio of helots to Spartans, and that was in the early iron age. I imagine the ratio could have been substantially worse in the neolithic and bronze ages. (Iron democratized violence compared to the bronze age, due to the lower cost of forging iron weapons. I'm sure neolithic violence had a different socioeconomic basis, but greater centralization of violence doesn't seem implausible.)
    - evincarofautumn 12y ago
      > Iron democratized violence compared to the bronze age Could you expand on this? If I have the resources to make an iron sword and you don’t, I can cut your bronze spearhead like butter. That doesn’t seem particularly democratic.
      - Perceval 12y ago
        During the Bronze Age, bronze weapons and armor were rarer. It cost more to mine and work bronze, and it cost more to buy a panoply. Therefore the distribution of those possessing the top-of-the-line violence capacity was concentrated in a narrow martial elite. The Iron Age broadened the number of people who could afford a panoply, because iron was easier to mine and cheaper to work (once they figured out how). The distribution of those with the ability to use force was a substantially broader elite, less concentrated than during the Bronze Age. When the ability to wield lethal violence becomes cheaper and available to a wider number of people, it's being "democratized." Samuel Colt's 1873 Single Action Army revolver is a more recent example of the democratization of violence capacity—“God made Men, but Samuel Colt made them all equal.” A similar argument can be made about the widespread availability of the cheap AK-47 following WWII.
        deciplex 12y ago
        Yep, that's why you meant "due to the higher cost of forging bronze weapons".
Balgair 12y ago
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 https://en.wikipedia.org/wiki/Y_chromosome
- brazzy 12y ago
  > 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.
  - Balgair 12y ago
    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.
    - brazzy 12y ago
      Gorillas form harem-like groups, but they're not as large, 3 to 6 females per male (often the groups have multiple related males). Chimps have dominant males, but females can and often do have sex with other males in the group. Bonobos are just ridiculously promiscous :) I just found a book called "Human Natures: Genes, Cultures, and the Human Prospect" which claims that southern elephant seals have harems of 48 females on average O_O - that's probably the record among mammals.
- 12y ago
netcan 12y ago
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.
- tjradcliffe 12y ago
  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.
  - dragonwriter 12y ago
    > 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.
glibgil 12y ago
You saw this coming? Just how old are you?
bluenose69 12y ago
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.186684.114.DC1/Supplemental_Figures.pdf http://genome.cshlp.org/content/suppl/2015/02/18/gr.186684.1...

swagasaurus-rex 12y ago

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.

bilbo0s 12y ago
This is the actual explanation. With one caveat... slavery. Basically, agriculture allowed people to specialize. This included specializing in killing. (Soldiers). You would use these specialists to conquer other lands. Which, in turn, provided slave labor to increase production in agriculture and other sectors. So the conquered females would be used as "rewards" for the conquerors. And the conquered males would be used to increase production across the conquering society via slave labor. So the explanation is pretty simple. In fact, the 17 to 1 figure is so low that I question whether they aren't missing something ??? Societies that developed later generally required enormous amounts of slave labor. That, coupled with the fact that there would have been an enormous amount of killing involved in taking the slaves in the first place, makes me wonder how the numbers turned out so evenhanded? I would have expected it to be an order of magnitude higher. But they did the study and have the data... so life must not have been quite as brutal as I thought it was. I suppose it is possible that life was brutal... and less desirable females simply may not have been taken? This happened a lot in our own history. Slave auction records show that some female slaves in America sold for as much as 100 times the rate of a "regular" female slave. (And even more in some private trades we have records for). We can speculate on why that may have been... but I think it's safe to assume that in a less sophisticated time they may have simply dispensed with females and males who were in some way undesirable, or were not likely to survive the journey back.
- Perceval 12y ago
  Sparta maintained a 10:1 ratio of helots to Spartans, and that was in the early iron age. I imagine the ratio could have been substantially worse in the neolithic and bronze ages. (Iron democratized violence compared to the bronze age, due to the lower cost of forging iron weapons. I'm sure neolithic violence had a different socioeconomic basis, but greater centralization of violence doesn't seem implausible.)
  - evincarofautumn 12y ago
    > Iron democratized violence compared to the bronze age Could you expand on this? If I have the resources to make an iron sword and you don’t, I can cut your bronze spearhead like butter. That doesn’t seem particularly democratic.
    - Perceval 12y ago
      During the Bronze Age, bronze weapons and armor were rarer. It cost more to mine and work bronze, and it cost more to buy a panoply. Therefore the distribution of those possessing the top-of-the-line violence capacity was concentrated in a narrow martial elite. The Iron Age broadened the number of people who could afford a panoply, because iron was easier to mine and cheaper to work (once they figured out how). The distribution of those with the ability to use force was a substantially broader elite, less concentrated than during the Bronze Age. When the ability to wield lethal violence becomes cheaper and available to a wider number of people, it's being "democratized." Samuel Colt's 1873 Single Action Army revolver is a more recent example of the democratization of violence capacity—“God made Men, but Samuel Colt made them all equal.” A similar argument can be made about the widespread availability of the cheap AK-47 following WWII.
      - deciplex 12y ago
        Yep, that's why you meant "due to the higher cost of forging bronze weapons".

Balgair 12y ago

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

brazzy 12y ago
> 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.
- Balgair 12y ago
  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.
  - brazzy 12y ago
    Gorillas form harem-like groups, but they're not as large, 3 to 6 females per male (often the groups have multiple related males). Chimps have dominant males, but females can and often do have sex with other males in the group. Bonobos are just ridiculously promiscous :) I just found a book called "Human Natures: Genes, Cultures, and the Human Prospect" which claims that southern elephant seals have harems of 48 females on average O_O - that's probably the record among mammals.
12y ago

netcan 12y ago

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.

tjradcliffe 12y ago
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.
- dragonwriter 12y ago
  > 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.

glibgil 12y ago

You saw this coming? Just how old are you?

bluenose69 12y ago

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.186684.114.DC1/Supplemental_Figures.pdf http://genome.cshlp.org/content/suppl/2015/02/18/gr.186684.1...