
Sudden Neolithic population drop was the result of brutal warfare: study - montrose
https://www.express.co.uk/news/science/967289/neolithic-population-drop-brutal-warfare-y-chromosome-scientists-research
======
Mbioguy
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).

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4381518/](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](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.

~~~
chiefalchemist
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?

~~~
nyolfen
>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'

~~~
bilbo0s
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.

~~~
chiefalchemist
> 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.

------
nostrademons
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.

~~~
solidsnack9000
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.

------
jdfellow
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.

~~~
posterboy
The rest of the world though? Especially in contrast ...

~~~
merdreubu
Maydanets, 4000 BC.

[https://en.wikipedia.org/wiki/Cucuteni%E2%80%93Trypillia_cul...](https://en.wikipedia.org/wiki/Cucuteni%E2%80%93Trypillia_culture#/media/File:Trypillian_city_\(Maydanets\).jpg)

Talianki, 4000 BC.

[https://en.wikipedia.org/wiki/Cucuteni%E2%80%93Trypillia_cul...](https://en.wikipedia.org/wiki/Cucuteni%E2%80%93Trypillia_culture#/media/File:Talianki_\(Trypillian_city\).jpg)

~~~
posterboy
... 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.

------
mabbo
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.

~~~
corey_moncure
Wouldn't the result be the human male that is the most adept at warfare?

~~~
Jare
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.

~~~
haihaibye
What happens to the men left at home of a conquered tribe?

~~~
barry-cotter
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.

------
jbattle
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.

~~~
Kalium
> 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.

------
varjag
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.

[https://en.wikipedia.org/wiki/Late_Bronze_Age_collapse](https://en.wikipedia.org/wiki/Late_Bronze_Age_collapse)

------
dkoubsky
Related: Humans have twice as many female ancestors as male ancestors.
[https://tierneylab.blogs.nytimes.com/2007/09/05/the-
missing-...](https://tierneylab.blogs.nytimes.com/2007/09/05/the-missing-men-
in-your-family-tree/)

~~~
TangoTrotFox
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.

~~~
kittiepryde
I've seen it as, 80% of women pass on their genes, but only 40% of men. (I
assume that's no longer true today)

~~~
smallnamespace
There is still a gender gap, but it's less extreme (on a percentage basis)
now:

 _By age 40, 85% of women had had a birth, and 76% of men had fathered a
child_

[https://www.cdc.gov/nchs/data/nhsr/nhsr051.pdf](https://www.cdc.gov/nchs/data/nhsr/nhsr051.pdf)

------
pvaldes
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

------
olivermarks
headline: 'scientists conclude'

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
We've added the qualifying ": study" bit above. Still, I think this is sort of
a nitpick.

~~~
AnimalMuppet
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.

~~~
posterboy
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.

~~~
AnimalMuppet
Sure, it's an obvious hypothesis. I just have a problem with reporting it like
it's proven.

------
galieos_ghost
survival of the fittest, the sexual dimorphism of humans and ingrained
tribalism should make it fairly obvious that conflict between groups was
common

------
z3t4
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.

------
kristaps
"The meek shall inherit the earth"
[https://en.wikipedia.org/wiki/Matthew_5:5](https://en.wikipedia.org/wiki/Matthew_5:5)

------
rjsw
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.

~~~
rjsw
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.

