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?
1. In addition to using public data, they sampled mitochondrial DNA and Y chromosomes from individuals in diverse geographical locations around the world (456 individuals). This had been done before for mtDNA but not Y chromosomes at anywhere near the level of resolution they attained. Phylogenetic tree analysis is performed to organize the variations into clades and estimate the genetic distance between them.
2. I'm very interested to know the answer to your second point myself. As displayed in figure 2, it looks like it wasn't exactly simultaneous or equal in magnitude everywhere. It does look like most geographic clusters did see something of a drop, at some point. Eyeballing it, it appears that the near-East and the Caucasus had the relatively most-significant drop. The African cluster appears to have had a more modest drop and at a later date. However, I wouldn't rely too heavily on trying to read more into the figures than the authors did (and as I just tried to do).
I suspect the resolving power their data sample gave them was insufficient to resolve your question. While it was enough to demonstrate the existence of such a drop, I would be skeptical of its power to demonstrate the relative severity or timing between each geographical cluster. (If I was the author, this finding would be begging for more grant money to do exactly that: gather more data and nail down exactly how much, when, and where the Y diversity was lost.)
Final point: it's not necessary to assume everyday life was brutal or violent. I'm not an anthropologist, so take my reference to Napoleon Chagnon with a grain of salt. The Amazonian Yanomamo people he lived among had high rates of violent death compared to other causes of death, yet everyday life was peaceful. Most of the bloodshed and conflict he documented occurred over very few days in quick moments. When a population is low, it doesn't take much to move the % up a lot.
Whatever caused the drop in Y diversity, if it happened over several thousand years, the yearly attrition rate could have been very low also.
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?
>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.
this replacement (sedentary agriculturalists killing/pushing out hunter-gatherers) happened everywhere in the world, not just 'white western europe'
Just eye-balling, but it does seem as though these drops in Y-diversity were far less extreme outside of europe and the mideast region.
That said, chiefalchemist is jumping to conclusions not supported by the data in the papers when he offers his conjectures on violence etc. The only thing we can really conclude with authority based on this data is that whatever happened, more of it happened in europe and the mideast.
> From the article: "It appears over the course of the next 2,000 years, the Old World male population plummeted to one-twentieth of what it had been beforehand"
With that said, let me rephrase then...the "rise" of the "violence gene profile":
1) Was more effective in some parts of the world then in others.
2) That profile is still with us today. Perhaps not as dominant but none rhe less not gone.
3) We may think we're a peace loving species but our gene pool says other wise.
Again, yesterday's "winning effort" is today's murder. Today's mental health issues arw yesterday's hero (e.g., an unfiltered willingness to kill).
We can talk about being rational, intelligent, etc. but the fact is we still have a gene pool that historically says otherwise.
In the long run there is never enough of any resource to go round. The population expands until there’s just barely enough, overshoots, collapses and then does it again and again or dies off. That’s the Malthusian trap.
The collapse of Y chromosome diversity around the transition to agriculture and civilisation is far from being exclusive to white or European culture. It happened in every human population that took up agriculture, to greater and lesser extent.
Violence is absolutely part of human nature. Serial killers are probably pathological but mass murder is definitely within normal human behaviour. The Mongols were less especially brutal than especially organised, ditto for the Nazis at a later date.
Kill everybody and take their land is more or less what happened to both the Neanderthals and the first H. Sapiens in Europe. Kill all the men is practically a humanitarian innovation.
"Violence is absolutely part of human nature. Serial killers are probably pathological but mass murder is definitely within normal human behaviour. The Mongols were less especially brutal than especially organised, ditto for the Nazis at a later date.
Kill everybody and take their land is more or less what happened to both the Neanderthals and the first H. Sapiens in Europe. Kill all the men is practically a humanitarian innovation."
That's the crux of my point. My sense is there's a perception that humans are "highly advanced" and that (e.g.) people with violent tendencies are highly "abnormal" and should - in extreme cases - be put to death.
The irony being their genes are what saved the species in previous generations. But today those genes are not advantageous.
Serial killers are dysfunctional people, acting more instinctually.
Systematic violence is ultimately very rational. Your worst enemy is always your neighbor or a trespasser. Agriculture requires ownership of land, so hunters are always the enemy of the farmer.
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.
(wiki was inexplicably deleted recently, i suspect for political reasons via rules lawyering)
> Geodakyan suggested that sex dimorphism gives a species the benefit of having two functional partitions, or subsystems. The male sex is considered an operative, variation subsystem, while the female sex is a conservative one. Sex differentiation allows a species to use the male partition to try out various genetic changes, including parasitic and cooperative co-existence for possible inter-species co-evolution and expansion of ecological niches. In Geodakyan's terms, species use males as an experimental partition of sex and use another partition (female) to maintain the features of the species that were proven to be beneficial.
This theory, though, seems a bit misguided. Binary sexual dimorphism is probably just the "stupidest thing that works" from an evolutionary perspective, and evolution is nothing if not pragmatic.
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.
... The rest of the world though? Maybe not caves, but tents or whatever. All the stone-built, permanent settlements you can come up with still leave enough room. I think it might as well be that stark contrast leading to domination (pun intended) rather than war between those cities that's suspect.
I was wondering about Europe specifically, so thanks for the links.
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.
Rather, the result would have the males less likely to die in war, which may include those most adept, those completely unable to partake, and those smart enough to find a way to skip it.
Many would be killed, some would be spared as useful, skilled labour like smiths, some would be spared. All would drop substantially in social status and likelihood of leaving descendants, bar skilled labour, if that.
You had a caste system in these civilizations. Warrior/hunters, farmers, priests, etc.
Neolithic civilization wasn’t just a band of 50 and a few yurts. There were complex societies, but they had scale limits due to technology and knowledge constraints.
ggggtez is not disagreeing with that. He is saying that when one society beats others at warfare, it is not because its males had more testosterone and larger muscles, rather because it had better agriculture and so on.
It's an argument of semantics at this point. I'm saying war isn't won by bigger muscles alone. If you can't feed your troops, or equip them with more efficient weapons and armor, and train them with better tactics, then you'll lose at "war" to a society which can.
I read a book on survival techniques when I was a teenager and it had a chapter on street fighting. It was prefaced with something like: the best way to win a fight is to not have one; pay attention to your surroundings and avoid getting into a situation where you have to fight. Run away if you can.
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.
Just as possible would be selection for _reduction_ in intelligence that reduces skepticism and limits thinking up objections to agitating emotion based calls for violence.
Likewise, lower intelligence might reduce personality differences and increased coordination. Individual troops with less foresight may be more careless of their own safety and thus more fierce on the battle field. In the manner of bees. Also, in a warrior society, obedience maybe favored over independent thinking.
Also, in an pre-agricultural societys everyone is a generalist: everyone must be smart enough to know how to do everything. Less true in agricultural societies.
So it's just as possible agriculture made people dumber but more dense population centers and thus more effective militarily.
My point is that barring actual measurement, we can conceive a great many possibilities and at this point no measurements indicate intelligence change over that period
I think this view is from a stereotyped but not really accurate view of warfare and it's reasons and execution. Warfare generally has very little to do with emotion. Even today, as always, it tends to be the same thing - one side has something and another side wants it. And in cases where you're not the side doing the taking, you need to be equally capable in war to defend what you have. Even things like religious warfare were more of a convenient casus belli for taking things than the cause entirely in and of themselves. This was a real risk all the way up until the 20th century. The thing that really changed the game was nukes which makes military dominance basically impossible, for now...
Similarly, throughout history it's invariably the more intelligent side that wins in war - at least in the longrun. The Mongols ended up wiping out a huge percent of the entire earth's population with an army that, for instance, when invading Europe only numbered in the low tens of thousands and were very lightly armored compared to the forces they were fighting. But they were smart in war and strategy and had relatively advanced technology in their composite bows. That the Mongoloid group of peoples to this day still have a substantially higher IQ than average I think is at least a reasonably strong correlation in support of selection for intelligence.
Neanderthals had larger brains than we do. If intelligence was the determining factor in out-competing rivals, we would expect all species to evolve greater intelligence at the cost of other adaptations. This is clearly not the case: only one species invented the gun, all others went with sharper teeth. Even now there are more sharks than dolphins, more reptiles than mammals, more insect than reptiles.
But in humans, the very idea that "we" fight to gain "their" requires creating an "us vs them" dichotomy. But all humans are the same species, and persons on national borders are invariably more closely related than on opposite sides of the same country.
Essentially every border is an accident of history: Romans building a wall, Charlemagne having so many heirs, monarchs marring one person vs another, religious boundaries becoming national ones, the treaty of Versailles drawing straight lines through deserts.
To convince people that a particular "us vs them" dichotomy is real requires the listener to have a certain kind of thinking processes. Especially to convince them to kill and die for it.
And because every population falls for this, any individual population that smartens up and notices it's absurd will likely be wiped out by those who still have the "us vs them" delusion. Thus the species is kept in a sub-optimal state.
That 19th century definition of Mongoloid is nonsensically arbitrary, so instead I was interpreting it in as generous a way as possible: residents of Mongolia or Haplogroup C3
The closest relatives of Genghis Khan, whom he claims is the source of superior intelligence, live overwhelmingly in modern day Mongolia and Kazakhstan. They are more related to Navajos than to modern Chinese, Japanese, Koreans or whoever else fits in that 19th century definition of "Mongoloid".
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.
Inversely a historian once explained to me that generally through history in order to take an area, you took the local village, or even city and there was a great deal less focus until later on specific borders or a campaign where your goal was tracts of land. Effectively if you took the city state, you generally had obtained the local surrounding land as well.... and if you didn't plan to keep the village or city, you destroyed it and the next nearest city or village was effectively the point of control.
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.'
No, it's more than a nitpick, and I think the correction is the wrong one. The study says that there was a Y-chromosome bottleneck, consistent with a very small number of males compared to the number of females. The "was the result of brutal warfare" part is speculation, not the result of the study.
It is probably a reference to the conclusion part of the paper, simply because it's an obvious hypothesis. It's not necessary that men died like flies, they just didn't procreate, but that's not mutually exclusive. Eitherway, it would be the result of competition with a social aspect.
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.
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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.