There's an interesting cognitive bias where people who are intelligent and informed about one domain, try to interpret information outside that domain. This stereotypically affects doctors or engineers making pronouncements of things as laypersons, and underestimating their own ignorance, commit errors without realizing it. Hacker News is an excellent place to get insight on technology. However, the lack of formal training often means that when other domains are discussed, we get armchair biologists or historians. That is happening here. (The loss of Y-diversity is much, much earlier in date than the Late Bronze Age collapse: starts at roughly 10k years ago, with a little variation depending on what part of the globe you are looking at.)
Here's the original article that caused such a stir in 2015. Figure 2 shows the sudden drop in the reproducing Y-population globally (meaning it cannot be explained by genes or migration).
The best current hypothesis to explain this drop (and that no similar one occurred for the reproducing X-population) is the conflict between predominantly agricultural societies versus predominantly hunter-gatherer societies. Until sufficient evidence has been found to rule out this or alternatives, take any explanation with a grain of salt.
Look at Figure 2, and you'll notice the Y-axis are different. Between 50-10kya, the effective reproductive population was 3-4 times larger for women than men, globally. This fits with modern anthropological evidence of polygyny in early hunter-gatherer cultures (loose polygyny with on average 3-4 wives per successful male over a lifetime, but with limited ability to enforce fidelity). Y chromosome diversity tends to accumulate, albeit at a lower rate than the X.
An agricultural community is likely to be much more homogenous in terms of Y-chromosomes, than a hunter-gatherer one. Power is much more effectively concentrated in these communities, allowing leaders to amass more wives and enforce fidelity much more strictly than in hunter-gatherer societies. Stories of King Solomon's wives, or Sultan Moulay Ismail of Morocco (who reportedly sired hundreds of children) are an easy way to visualize this.
While man-for-man, a hunter-gatherer may be healthier and stronger, a hunter-gatherer society may find themselves vastly outnumbered by an agricultural community. Over time, hunter-gatherers would find themselves pushed off of prime land onto marginal land. The newer article mentions a founder effect. Where are these Neolithic pioneers coming from and where are they going to? From agricultural communities, expanding into territory previously held by hunter-gatherers. While certainly many deaths occurred due to combat, Y-chromosomal diversity loss also would have occurred to disease and famine. The agricultural population would continue to rise, while the hunter-gatherers would struggle to maintain on more marginal land. History is replete with stories of taking women, so if this scenario is the best explanation, it is unsurprising that there was not a corresponding drop in X-diversity.
This sort of scenario occurred globally. Agriculture independently arose in many places: the near-east, sub-saharan Africa, China, Mexico, the Andes, and possibly others. We've seen what happened to the Americas after Columbus. Similar mechanisms help explain the population-level Y-cide on smaller scales that probably occurred during each of the agricultural expansions above.
This hypothesis, while probably the most widely-accepted at present, is challenged by some of the evidence in the newer paper. It will be interesting to see how it falls out once the original authors have a chance to respond or additional voices join the conversation.
Your first paragraph is gold. It succinctly summarizes some of the problems with reactions to science articles on HN - especially science articles in certain subject areas.
1. How, in layman's terms, are they reconstructing the history of the genomes from current genome samples? (I think that's what the paper you mention says, but I'm not sure.)
2. My understanding is that the creation of agriculture was separated by thousands of years between the centers (near East, China, etc.), followed by thousands of years spreading from each center. The figure in your first paper makes the bottleneck appear essentially simultaneous world-wide. What's up with that?
The first paragraph is fun to read: someone on HN says people on HN are not competent to comment on the subject except for him/her.
Seriously, you might have missed it but people on HN have an astonishing variety of professional backgrounds. On many occasions, I've read the most enlightening comment on some news here on HN.
Also slavery, I bet. Standard practice for victors was killing all defeated adult males, and taking everyone else as slaves. Females got to breed as wives or prostitutes. Young males were sometimes castrated.
It sounds reasonable, but I get lost on the idea that there wasn't enough land to go around. Small populations and plenty of land / resources. Why fight?
That said, would it be (semi) safe to presume that the most fittest survived, and those likely being the most (for lack of a better term) ruthless? That is, the gene pool (on the male side) leaned towards violence (as a means of survival). That in turn served as the foundation of white Western Europe repeatedly exerting itself as a superior culture.
And at the extremes, this helps explains serial killers, mass murders, etc. That is, today's violence was yesterday's survival skills. Some of those genes remain in the gene pool. At least in theory, yes?
other explanations included, its no surprise that there's a sudden die off of male lineages in the Y with agriculture coming into the scene.
to me, its another example of yin/yang creation/destruction push/pull where males drive evolution through destruction and females preserve the species dna.
Note that the observed genetic variance can be explained without any substantial drop in population (male or total):
Assume that humans are living in patrilineal clans of roughly 20 males and an equivalent number of females. All males are genetic descendants of the clan patriarch and share the same Y-chromosome markers. All females are born outside the clan and marry into it.
Now assume that 95% of clans are wiped out through a couple millenia of warfare. That Y-chromosome is now extinct; all male-line descendants of the patriarch are dead. However, genetic markers carried by the female are not extinct, because the 20 daughters born into the clan have married into 20 different clans, and at least one of them has survived.
Note that the population doesn't actually have to drop in this scenario! 95% extinction of clans over 2000 years implies only 0.15% extinction annually, assuming an exponential decay. If warfare is continuous and resources go to the victor, then one clan is exterminated, but the victorious clan quickly doubles in size as it takes the dead clan's resources (and oftentimes, womenfolk). Total population remains roughly constant, but all living descendants come from a tiny percentage of male ancestors.
Other articles about this study have made this distinction explicitly (or at least hinted about it), but it's totally missing from the headline.
So assuming that clans tend to get wiped out all of a piece, and males cross clans much less frequently than clans get wiped out, many of the Y-chromosome lines will go extinct, but few of the mitochondrial DNA lines will go extinct?
There are a very few matrilocal human societies; perhaps they show the obverse pattern.
I'm somewhat bothered by the fact that the illustration is of "cavemen" and video of someone recreating paleolithic technologies.
The neolithic period was one of agriculture and early civilization. Stonehenge was built by neolithic peoples, and Egypt, Mesopotamia and China were embryonic civilizations in the neolithic era as well. Cavemen, these were not.
I agree. Here's the actual study at Nature ("Cultural hitchhiking and competition between patrilineal kin groups explain the post-Neolithic Y-chromosome bottleneck
"): https://www.nature.com/articles/s41467-018-04375-6
Maybe the URL for this submission could be changed?
That video[1] is part of a series by this guy who is out recreating technology literally from dirt. If you're a prepper you want this guy on your team, you'll advance to the castle age way before anyone else does :-)
The Daily Express is quite a long way from being a serious newspaper. I don't know US papers but it's probably somewhere around what would happen if Fox News put out a print edition.
2000 years of warfare between males is more than enough time for natural selection to start taking place. I wonder if the resulting human male is one less prone to aggression and warfare?
Maybe the reason civilization is even possible today is that the majority of our potential ancestors who couldn't deal with civilized life wiped each other out. Or alternatively, the males who survived were really good at warfare and surviving warfare.
I'd expect mostly the latter. In war to the victor go the spoils, and that would have included the women. Consider Genghis Khan - it's been estimated that he has about 16 million living descendents today.
But beyond the warfare stuff, another key selector would have been intelligence. Give two groups of people sticks and stones and I'm betting on the smarter. You don't need much strength to kill with even those weapons, and all the strength in the world isn't going to help you when you get hit. Perhaps it's the case that we still some of this today as it relates to Genghis Khan as the mongoloid group of peoples tend to have some of the highest average visual/spatial IQs on the planet.
Guns, Germs and Steel had an interesting theory that as societies increased in complexity and size, warfare became more likely to take place away from the main population centers and therefore less damaging. Two tribes go to war its pretty easy to end up destroying every piece of infrastructure from both so there wasn't a ton of investment in it when we were just tribes.
So not so much surviving warfare as much as an increasing capability to control it so it took place away from the productive infrastructure. A pattern we see to this day.
Maybe I'm misunderstanding the article - but it sounds like there was a drop of 95% in the population of males living in Europe / Africa / Asia?
What kind of World War Zero could possibly explain this? I really can't picture how a state of sustained (for thousands of years?) high-intensity warfare over an area spanning three entire continents could have worked. How many historical instances are there of a population decreasing to 1/20th of previous levels? The 20th century had a couple of instances but that required totalitarianism and modern communication, logistics, and industrial capabilities.
The other historical instance I know of is the decimation of New World populations after contact with Europe (through disease). I don't know what other evidence they've assembled, but disease feels like a much better way to explain this population drop than warfare.
But what diseases only target males? Dunno. Maybe the early domestication of livestock introduced some kind of chickenpox or dogpox that killed (or sterilized!) males dramatically more frequently than females.
> But what diseases only target males? Dunno. Maybe the early domestication of livestock introduced some kind of chickenpox or dogpox that killed (or sterilized!) males dramatically more frequently than females.
Wolbachia is a parasite that, as I understand it, kills male infected at a very young age. Now, this only affects insects, but it does show that something this level of sex-selective is possible.
It wasn’t a 95% drop in male population. The population expanded rapidly but which men reproduced was very lopsided. Some men left no descendants because their folk didn’t stop hunter gathering and were eventually killed or starved. Some left many, kings and warlords. In between were everyone else.
One common feature of all the theories I've seen is that the warfare isn't all that high intensity. On the other hand, it does seem strangely sustained, widespread, and in a narrow time span.
Interesting to see DNA forensic methods substitute for traditional anthropologic and historical studies. The next wave of social collapse was much better known due to established lore and culture.
I think that headline is very easy to misunderstand. Less interesting, but more accurate headline: Men have offspring with more different partners than women do. So there are more unique women in the family tree of humanity than men. Of course the number of men and women as direct ancestors is identical if we ignore repeats.
Or maybe you can't hunt to extinction most big mammal european fauna without fireweapons, including lions, sabertooth, european elephants, european rhinoceros, uros, several species of bison, huge cave bears, european black bears, wolves, tigers etc, without losing a lot of young men in the process
Article
'A SUDDEN and dramatic drop in the number of human males living in Europe, Africa, and Asia 7,000 years ago is evidence of brutal warfare spanning multiple generations, a new study has suggested.'
Probably because the son inherited the land. And daughters where married away. If you run this simulation a couple of generations you will probably get similar results.
The recent articles on the "incel" movement made me wonder whether pressures to encourage monogamy were the cause of modern civilization, by allowing a greater variety of male genotypes to reproduce.
To clarify, I'm a left-wing atheist. I think that a big priority is to reduce the world population, if the easiest way to do that is by improving women's lives then great.
I think we also need to recognize how we got to this point though.
[+] [-] Mbioguy|7 years ago|reply
Here's the original article that caused such a stir in 2015. Figure 2 shows the sudden drop in the reproducing Y-population globally (meaning it cannot be explained by genes or migration).
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4381518/
The paper cited in the article alters the date of the event, but really there's a lot of uncertainty remaining.
https://www.nature.com/articles/s41467-018-04375-6
The best current hypothesis to explain this drop (and that no similar one occurred for the reproducing X-population) is the conflict between predominantly agricultural societies versus predominantly hunter-gatherer societies. Until sufficient evidence has been found to rule out this or alternatives, take any explanation with a grain of salt.
Look at Figure 2, and you'll notice the Y-axis are different. Between 50-10kya, the effective reproductive population was 3-4 times larger for women than men, globally. This fits with modern anthropological evidence of polygyny in early hunter-gatherer cultures (loose polygyny with on average 3-4 wives per successful male over a lifetime, but with limited ability to enforce fidelity). Y chromosome diversity tends to accumulate, albeit at a lower rate than the X.
An agricultural community is likely to be much more homogenous in terms of Y-chromosomes, than a hunter-gatherer one. Power is much more effectively concentrated in these communities, allowing leaders to amass more wives and enforce fidelity much more strictly than in hunter-gatherer societies. Stories of King Solomon's wives, or Sultan Moulay Ismail of Morocco (who reportedly sired hundreds of children) are an easy way to visualize this.
While man-for-man, a hunter-gatherer may be healthier and stronger, a hunter-gatherer society may find themselves vastly outnumbered by an agricultural community. Over time, hunter-gatherers would find themselves pushed off of prime land onto marginal land. The newer article mentions a founder effect. Where are these Neolithic pioneers coming from and where are they going to? From agricultural communities, expanding into territory previously held by hunter-gatherers. While certainly many deaths occurred due to combat, Y-chromosomal diversity loss also would have occurred to disease and famine. The agricultural population would continue to rise, while the hunter-gatherers would struggle to maintain on more marginal land. History is replete with stories of taking women, so if this scenario is the best explanation, it is unsurprising that there was not a corresponding drop in X-diversity.
This sort of scenario occurred globally. Agriculture independently arose in many places: the near-east, sub-saharan Africa, China, Mexico, the Andes, and possibly others. We've seen what happened to the Americas after Columbus. Similar mechanisms help explain the population-level Y-cide on smaller scales that probably occurred during each of the agricultural expansions above.
This hypothesis, while probably the most widely-accepted at present, is challenged by some of the evidence in the newer paper. It will be interesting to see how it falls out once the original authors have a chance to respond or additional voices join the conversation.
[+] [-] mturmon|7 years ago|reply
[+] [-] mcguire|7 years ago|reply
1. How, in layman's terms, are they reconstructing the history of the genomes from current genome samples? (I think that's what the paper you mention says, but I'm not sure.)
2. My understanding is that the creation of agriculture was separated by thousands of years between the centers (near East, China, etc.), followed by thousands of years spreading from each center. The figure in your first paper makes the bottleneck appear essentially simultaneous world-wide. What's up with that?
[+] [-] stewbrew|7 years ago|reply
Seriously, you might have missed it but people on HN have an astonishing variety of professional backgrounds. On many occasions, I've read the most enlightening comment on some news here on HN.
[+] [-] mirimir|7 years ago|reply
[+] [-] chiefalchemist|7 years ago|reply
That said, would it be (semi) safe to presume that the most fittest survived, and those likely being the most (for lack of a better term) ruthless? That is, the gene pool (on the male side) leaned towards violence (as a means of survival). That in turn served as the foundation of white Western Europe repeatedly exerting itself as a superior culture.
And at the extremes, this helps explains serial killers, mass murders, etc. That is, today's violence was yesterday's survival skills. Some of those genes remain in the gene pool. At least in theory, yes?
[+] [-] autokad|7 years ago|reply
other explanations included, its no surprise that there's a sudden die off of male lineages in the Y with agriculture coming into the scene.
to me, its another example of yin/yang creation/destruction push/pull where males drive evolution through destruction and females preserve the species dna.
[+] [-] goptimize|7 years ago|reply
[+] [-] nostrademons|7 years ago|reply
Assume that humans are living in patrilineal clans of roughly 20 males and an equivalent number of females. All males are genetic descendants of the clan patriarch and share the same Y-chromosome markers. All females are born outside the clan and marry into it.
Now assume that 95% of clans are wiped out through a couple millenia of warfare. That Y-chromosome is now extinct; all male-line descendants of the patriarch are dead. However, genetic markers carried by the female are not extinct, because the 20 daughters born into the clan have married into 20 different clans, and at least one of them has survived.
Note that the population doesn't actually have to drop in this scenario! 95% extinction of clans over 2000 years implies only 0.15% extinction annually, assuming an exponential decay. If warfare is continuous and resources go to the victor, then one clan is exterminated, but the victorious clan quickly doubles in size as it takes the dead clan's resources (and oftentimes, womenfolk). Total population remains roughly constant, but all living descendants come from a tiny percentage of male ancestors.
Other articles about this study have made this distinction explicitly (or at least hinted about it), but it's totally missing from the headline.
[+] [-] solidsnack9000|7 years ago|reply
There are a very few matrilocal human societies; perhaps they show the obverse pattern.
[+] [-] jdfellow|7 years ago|reply
The neolithic period was one of agriculture and early civilization. Stonehenge was built by neolithic peoples, and Egypt, Mesopotamia and China were embryonic civilizations in the neolithic era as well. Cavemen, these were not.
[+] [-] benbreen|7 years ago|reply
Maybe the URL for this submission could be changed?
[+] [-] ChuckMcM|7 years ago|reply
[1] https://www.youtube.com/watch?v=VVV4xeWBIxE
[+] [-] firmgently|7 years ago|reply
[+] [-] posterboy|7 years ago|reply
[+] [-] mabbo|7 years ago|reply
Maybe the reason civilization is even possible today is that the majority of our potential ancestors who couldn't deal with civilized life wiped each other out. Or alternatively, the males who survived were really good at warfare and surviving warfare.
[+] [-] corey_moncure|7 years ago|reply
[+] [-] TangoTrotFox|7 years ago|reply
But beyond the warfare stuff, another key selector would have been intelligence. Give two groups of people sticks and stones and I'm betting on the smarter. You don't need much strength to kill with even those weapons, and all the strength in the world isn't going to help you when you get hit. Perhaps it's the case that we still some of this today as it relates to Genghis Khan as the mongoloid group of peoples tend to have some of the highest average visual/spatial IQs on the planet.
[+] [-] philipodonnell|7 years ago|reply
So not so much surviving warfare as much as an increasing capability to control it so it took place away from the productive infrastructure. A pattern we see to this day.
[+] [-] jbattle|7 years ago|reply
What kind of World War Zero could possibly explain this? I really can't picture how a state of sustained (for thousands of years?) high-intensity warfare over an area spanning three entire continents could have worked. How many historical instances are there of a population decreasing to 1/20th of previous levels? The 20th century had a couple of instances but that required totalitarianism and modern communication, logistics, and industrial capabilities.
The other historical instance I know of is the decimation of New World populations after contact with Europe (through disease). I don't know what other evidence they've assembled, but disease feels like a much better way to explain this population drop than warfare.
But what diseases only target males? Dunno. Maybe the early domestication of livestock introduced some kind of chickenpox or dogpox that killed (or sterilized!) males dramatically more frequently than females.
[+] [-] Kalium|7 years ago|reply
Wolbachia is a parasite that, as I understand it, kills male infected at a very young age. Now, this only affects insects, but it does show that something this level of sex-selective is possible.
[+] [-] haihaibye|7 years ago|reply
Imagine tribes filled out over populated Europe like cells. They raid each other, kill men, take women and now that Y chromosome fills 2 cells.
Push an exponentially increasing 1 tribal diameter of area per generation at the front and it doesn't take many generations for almost replacement.
[+] [-] barry-cotter|7 years ago|reply
[+] [-] mcguire|7 years ago|reply
[+] [-] varjag|7 years ago|reply
https://en.wikipedia.org/wiki/Late_Bronze_Age_collapse
[+] [-] dkoubsky|7 years ago|reply
[+] [-] TangoTrotFox|7 years ago|reply
[+] [-] unknown|7 years ago|reply
[deleted]
[+] [-] pvaldes|7 years ago|reply
[+] [-] olivermarks|7 years ago|reply
Article 'A SUDDEN and dramatic drop in the number of human males living in Europe, Africa, and Asia 7,000 years ago is evidence of brutal warfare spanning multiple generations, a new study has suggested.'
Theory is fact in click bait tabloid headlines...
[+] [-] dang|7 years ago|reply
[+] [-] posterboy|7 years ago|reply
a new study has suggested, terminal qualifiers are often ignored
[+] [-] galieos_ghost|7 years ago|reply
[+] [-] z3t4|7 years ago|reply
[+] [-] kristaps|7 years ago|reply
[+] [-] rjsw|7 years ago|reply
[+] [-] rjsw|7 years ago|reply
I think we also need to recognize how we got to this point though.