
Massive genetic study shows how humans are evolving - gwern
https://www.nature.com/news/massive-genetic-study-shows-how-humans-are-evolving-1.22565
======
Will_Parker
Now that we have access to the entire genome directly, instead of relying on
twin and adoption studies, we are going to get many more of these insights.
And it's not all going to be comfortable. There will be cries of biological
essentialism, while the blank slate idea is no longer one that can be held by
an educated rational person.

On more controversial lines, see this
[http://www.biorxiv.org/content/early/2017/09/06/184853.1](http://www.biorxiv.org/content/early/2017/09/06/184853.1)
study (N=280,000) that correlates specific genes with IQ.

~~~
Arcsech
There are two big risks, as I see it: 1) the human tendency to turn
statistical averages into absolutes. Imagine genetic testing saying that gene
A is associated with a slightly higher than average propensity for coding
ability (say, 3%). Then we see people saying "Oh you can't code? Must not have
gene A!" Or genetic testing revealing that someone doesn't have gene A, so
they're told they can't code, even though they could very well have been great
at it. All because of an extra 3% probability.

2) Making it impossible/unbearably expensive for people with genes that are
correlated with higher risk of whatever conditions to get health
care/insurance.

We need to be really careful with how we talk about genetic insights as we
gain more and more understanding, as well as what uses of that information we
allow, or we're going to get ourselves into another period of atrocities
justified by what boils down to eugenics. Perhaps not on the scale of genocide
of entire populations, but still bad enough.

~~~
zo1
I'd add 3) A Genetic arms race between nation states.

It's only a matter of time before a nation state starts spending a not-so-
insignificant amount of money on IVF + DNA-based screening to start picking
good genetic offspring for their populace. It's only going to start becoming
more and more plausible the cheaper we make this technology.

Very awkward and important questions/decisions await us in the near future.

~~~
tosser350
China already paid people with high intelligence to ship them DNA for research
in 2013, they are already doing embryo gene manipulation. They are years ahead
of us due to not caring about ethics. Political correctness will be the death
of the west.

[https://www.nature.com/news/chinese-project-probes-the-
genet...](https://www.nature.com/news/chinese-project-probes-the-genetics-of-
genius-1.12985)

~~~
mcbits
Different ethics != not caring about ethics. And if not caring about ethics
were the key to winning the nation-state game, the ethical response would be
to tear it all down ASAP, which is usually quite unethical in practice.

~~~
dTal
I'm not sure I follow your argument. Tearing it all down is or isn't ethical,
therefore not caring about ethics is not the key to winning the nation-state
game?

~~~
mcbits
Ethics is stuck between a rock and a hard place if nations collapse _because_
they're not disregarding ethics enough, as the previous comment suggests. (I'm
disputing the premise.)

------
riazrizvi
I found the article confusing, I don't understand the link between the paper
and evolution: 1\. APOE-Alzheimer-propensity gene is a new gene, emerging in
the younger population. (Clearly, prevalence of this gene reduces a person's
life-expectancy but not until they are done giving birth). 2\. Same with
CHRNA3-heavy-smoking-propensity gene. 3\. These genes are not evolutionary
drivers since they don't effect E[number of offspring] or E[survival rate
until given birth to final offspring]. 4\. From an evolutionary perspective,
prevalence of these genes should be found in equal proportion across all ages
of the population. 5\. Then why are these genes emerging? Isn't it far more
likely that there is some new factor in our lifestyle/diet/habitat etc that is
causing the gene to appear in the population? Which has nothing to do with
evolution. Where in the paper do they talk about evolution?

~~~
perlgeek
The confusing part is that we are used to thinking about evolution as spanning
multiple generations: a gene increases fitness, so its prevalence increases
over the generations. Or the flip side: it decreases fitness, so the members
that have it reproduce less, its prevalence decreases.

But this study takes a snapshot of a population, and looks at gene prevalence
as a function of age. So what you see are not effects of reproduction, but
rather on survival. It finds the Alzheimer's gene less in 70 year olds,
because those with the gene are more likely to have died earlier, and thus not
appear in the study.

Thus your statement "APOE-Alzheimer-propensity gene is a new gene" is likely
not true. It is likely just as prevalent in the current generation as two
generations before; just those individuals from two generations before who had
it are more likely to be already dead.

So the study looks at how genes influence survival rates -- something that is
very obviously related to evolution if it occurs before reproduction. If
survival rates only depend on some genes in higher age, they have only small,
second-order effects on reproduction (like a child being more likely to
survive if it has healthy grandparents or parents).

(Disclaimer: I'm not a biologist, so take this with a grain of salt).

~~~
riazrizvi
I suppose that does explain the drop off in expression of the gene:
Alzheimer's risk of death/year 1-3% [1]. That annual mortality rate is in the
right ballpark to explain the frequency of gene expression decrease by about
50% between ages 40 and 80 [2].

Agree the study does look at genes influencing survival rates. I still don't
see the link to the headline 'humans are evolving!'. Small second-order
effects, okay, sure. So how about, 'Massive Genetic Study shows genetics
affect mortality rates, plus maybe there's a small secondary effect on
reproduction, who knows?'.

[1]. 83,000 (i) or 3,349 (ii) Alzheimer's deaths per year out of 2mm deaths
(iii) => 1-3%

i) [http://www.nydailynews.com/life-style/health/alzheimer-
kills...](http://www.nydailynews.com/life-style/health/alzheimer-kills-
previously-thought-study-article-1.1712078)

ii)
[http://www.alz.org/mglc/in_my_community_60862.asp](http://www.alz.org/mglc/in_my_community_60862.asp)

iii)
[https://www.cdc.gov/nchs/fastats/deaths.htm](https://www.cdc.gov/nchs/fastats/deaths.htm)

[2] See graphs in paper.

~~~
mirimir
I'm confused. Sure, they identified two alleles with occurrence that decreases
with age. And sure, that does suggest that those alleles reduce survival rate.

But to demonstrate evolutionary change, they'd need data on occurrence of
these alleles as a function of birth date, stratified by age. It'll take some
time to get such data. Probably at least a few decades.

------
cowpig
> But if that were the case, there would be plenty of such mutations still
> kicking around in the genome, the authors argue. That such a large study
> found only two strongly suggests that evolution is “weeding” them out, says
> Mostafavi, and that others have probably already been purged from the
> population by natural selection.

This seems like a lot of speculative leaps to me.

1\. assuming that they should necessarily find many of these correlations,
absent evolutionary elimination (maybe the effects of individual groups of
genes just aren't that strong?)

2\. assuming that the lack of them indicates that they existed before and were
eliminated (maybe they never existed at all?)

3\. more generally, assuming that evolutionary selection is a determining
factor in the data they're studying at all (I don't often see noticeable
changes in a few generation in highly-contrived genetic algorithms I play
with, let alone real-world data which has way, way more noise)

------
ronnier
* Analysis of 215,000 people's DNA suggests variants that shorten life are being selected against.

* tested more than 8 million common mutations, and found two that seemed to become less prevalent with age. A variant of the APOE gene, which is strongly linked to Alzheimer’s disease, was rarely found in women over 70. And a mutation in the CHRNA3 gene associated with heavy smoking in men petered out in the population starting in middle age. People without these mutations have a survival edge and are more likely to live longer, the researchers suggest.

* certain groups of genetic mutations, which individually would not have a measurable effect but together accounted for health threats, appeared less often in people who were expected to have long lifespans than in those who weren't. These included predispositions to asthma, high body mass index and high cholesterol.

* Most surprising, however, was the finding that sets of mutations that delay puberty and childbearing are more prevalent in long-lived people.

~~~
mannykannot
This puzzled me, as these Alzeheimer's and smoking results do not seem to be
evidence of evolution; one would surely need to see a decrease over
generations? The article goes on to say 'That such a large study found only
two [late-acting genes] strongly suggests that evolution is “weeding” them
out, says Mostafavi, and that others have probably already been purged from
the population by natural selection.' The article and paper then repeat some
hypotheses as to why natural selection would eliminate these hypothesized
former late-acting genes from the gene pool, given that they seem to act after
most people's reproductive years.

So the article and paper seem to be arguing that a _low_ frequency of late-
acting genes indicates ongoing evolution, but acknowledge that this raises
questions about why natural selection would act on them.

The relevance of the decrease of the prevalence of these genes with age is
apparently that survivorship bias is being used to distinguish causation from
mere correlation.

~~~
skookumchuck
An Attenborough TV show suggested that the reason people live long compared to
animals is that grandparents are needed to help raise the young. The
grandparents raise the young while the parents work/hunt/farm/whatever.

So having healthy grandparents gives a survival advantage.

~~~
fauigerzigerk
This theory is mentioned in the article as well, but it doesn't seem very
plausible if we're talking about living into the 80s or 90s.

At that age, the effect should be reversed as people often need care
themselves rather than caring for grandchildren (who may be adults by that
time anyway)

I suppose the "grandmother theory" originally only explained why women live
beyond menopause, not into their 70s, 80s or 90s.

~~~
skookumchuck
Primitive societies are known to abandon old people to die when they become a
burden rather than an asset.

~~~
ch4s3
some

~~~
skookumchuck
What's a nomadic tribe to do with someone who can no longer keep up? When
there is insufficient food (commonplace in older societies) who is going to
get the food?

When resources get scarce, there are a lot of ugly realities.

~~~
dredmorbius
You might do better to provide citations over argument.

~~~
skookumchuck
"Traditional nomadic tribes often end up abandoning their elderly during their
unrelenting travels. The choice for the healthy and young is to do this or
carry the old and infirm on their backs — along with children, weapons and
necessities — through perilous territory. Also prone to sacrificing their
elderly are societies that suffer periodic famines. Citing a dramatic example,
Diamond said Paraguay’s Aché Indians assign certain young men the task of
killing old people with an ax or spear, or burying them alive."

[http://newsroom.ucla.edu/stories/jared-diamond-on-
aging-1505...](http://newsroom.ucla.edu/stories/jared-diamond-on-aging-150571)

~~~
dredmorbius
Thanks, exactly.

------
NyxWulf
I agree with the premise, these reports seem to focus on the act of passing
your genetic material to a child as the final act. Anyone who has had kids
knows that passing on your genes is the easy part, raising them to be
productive members of society who will in turn procreate takes a long time and
you continue to influence and guide them. So something that shortens your
lifespan would reduce the survival edge of the remaining offspring compared to
a group with that guiding influence.

This is a pretty clear social structure in humans. I understand not all or
even most animals have that same social structure. Can someone explain to me
why they would assume remaining alive after you dump off your genetic material
would be neutral? (from an evolutionary perspective)

~~~
tempestn
This is addressed in the article:

 _Why these late-acting mutations might lower a person’s genetic fitness —
their ability to reproduce and spread their genes — remains an open question.

The authors suggest that for men, it could be that those who live longer can
have more children, but this is unlikely to be the whole story. So scientists
are considering two other explanations for why longevity is important. First,
parents surviving into old age in good health can care for their children and
grandchildren, increasing the later generations’ chances of surviving and
reproducing. This is sometimes known as the ‘grandmother hypothesis’, and may
explain why humans tend to live long after menopause. _

------
Udik
Can someone explain this to me? The article says: "People who carry a harmful
genetic variant die at a higher rate, so the variant becomes rarer in the
older portion of the population." However, this is the opposite of how I
understand evolution: "harmful" variants (from the evolutionary point of view)
should become rarer in the younger portion of the population- whatever happens
to their original carriers is irrelevant.

Also "researchers scoured large US and UK genetic databases"\- well, I
wouldn't be too sure that the biggest part of evolution happening in the human
species can be seen inside the UK and US genetic databases.

------
marcelsalathe
Direct link to paper (OA):
[http://journals.plos.org/plosbiology/article?id=10.1371/jour...](http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2002458)

------
hellofunk
> one of the first attempts to probe directly how humans are evolving over one
> or two generations.

Considering the extraordinary amount of time it takes for evolution to do
anything at all, that they can quantify it in what is relatively zero time in
the span of life on Earth, seems to remarkable to be true.

~~~
vanderZwan
This is a very, very stubborn idea about evolution that has proven to be kind
of false. Rapid evolution exists, and we can observe evolution happening in
many species:

[http://discovermagazine.com/2015/march/19-life-in-the-
fast-l...](http://discovermagazine.com/2015/march/19-life-in-the-fast-lane)

As I understand, the simplest explanation for species being so _stable_ over
millions of years (like, say, sharks) is that while evolution can happen quite
fast, it "averages itself out" \- there's a kind of regression-to-the-mean
effect.

~~~
hellofunk
I have been taught something different in school, but that was a while ago, so
perhaps the field has evolved some in recent years. That, depending on the
species, evolution rarely occurs between generations, and that it leans on
large changes that are sudden and far between, and these changes are not at
the same time for each species. That is to say, evolution is not usually a
linear process for which at any point in time there is a delta. It is more of
a stair step.

That is part of what makes the report hard to believe, even if it is a novel
idea and has some other merits.

Not to say it couldn't be true, but as I expressed, it seems remarkable that
such evidence was found in a single generational study.

~~~
vanderZwan
You're right that it is a relatively recent development: the first papers
(cautiously) going against this idea of evolution happening slowly started
appearing in the middle of the last century. The first paper flat-out stating
evolution was observed within a few generations was in the late 1970s
(mentioned in the linked article in my previous post). So you can imagine it
would take a while for the field to accept this new attitude, let alone how
long it takes for this new knowledge to then diffuse into the rest of society.

Either way my comment certainly wasn't intended as a critique aimed at you!

Also, thinking about it some more, it's not that strange that the idea of slow
evolution hasn't died out yet, because it's not so much wrong as that reality
more complicated and really counter-intuitive than what you think if you
_only_ look at fossils[0]:

> _In the 1950s, the Finnish biologist Björn Kurtén noticed something unusual
> in the fossilized horses he was studying. When he compared the shapes of the
> bones of species separated by only a few generations, he could detect lots
> of small but significant changes. Horse species separated by millions of
> years, however, showed far fewer differences in their morphology. Subsequent
> studies over the next half century found similar effects — organisms
> appeared to evolve more quickly when biologists tracked them over shorter
> timescales._

> _Then, in the mid-2000s, Simon Ho, an evolutionary biologist at the
> University of Sydney, encountered a similar phenomenon in the genomes he was
> analyzing. When he calculated how quickly DNA mutations accumulated in birds
> and primates over just a few thousand years, Ho found the genomes chock-full
> of small mutations. This indicated a briskly ticking evolutionary clock. But
> when he zoomed out and compared DNA sequences separated by millions of
> years, he found something very different. The evolutionary clock had slowed
> to a crawl._

(I have to apologise for not remembering this article yesterday, it would have
made things more clear)

So in retrospect my "very stubborn idea" assessment is probably a bit unfair.

But, back to what we were taught in school. Caveat: I'm not a biologist, let
alone evolution expert, just a nerd who is into this topic. There are a number
of issues with the description you gave (which, for the record, fits with how
it was taught to me in high-school)

It is true that evolution is not linear, but being taught that evolution is a
stair step is just as bad. It (implicitly) assumes evolution is a form of
_progress_. It's not, it's just adaptation. The simplest of life forms that
exist nowadays are just as successful as we are, in the sense that they also
didn't go extinct and will continue to thrive in the future. On the other end
of the spectrum you actually can have runaway adaptation, especially when
there's a kind of "arms race" between predator and prey. The cheetah is so
hyper-specialised for catching its prey by speed alone that it's a kind of
evolutionary dead-end; it can't zig-zag like the gazelle can. Anyway, the
stair-step attitude originates from outside of biology, from Platonic thinking
that there are "higher" ideal forms.

And the sudden changes turn out not to be "few and far between", they just
don't seem to stick. Most adaptations average out, because they're highly
contextual to their short time periods. As mentioned, since we based our first
ideas about evolution on fossils, we only noticed the slow evolution. Sex
actually seems to play a large part in the filtering process[1]:

> _For a species whose numbers show no signs of collapsing, humans have a
> shockingly high mutation rate. Each of us is born with about 70 new genetic
> errors that our parents did not have. That’s much more than a slime mold,
> say, or a bacterium. Mutations are likely to decrease an organism’s fitness,
> and an avalanche like this every generation could be deadly to our species.
> The fact that we haven’t gone extinct suggests that over the long term, we
> have some way of taking out our genetic garbage. And a new paper, recently
> published in Science, provides evidence that the answer may be linked to
> another fascinating procedure: sex. (...) As the number of nasty genetic
> errors in a population rises, natural selection will sweep large rafts of
> them out of the genome together. And in sexual organisms, because of the
> ways that mutations from each parent can recombine randomly onto the same
> chromosomes, the synergistic elimination of bad mutations can happen even
> faster._

Anyway, hope this addresses some of your understandable scepticism!

[0] [https://www.quantamagazine.org/evolution-runs-faster-on-
shor...](https://www.quantamagazine.org/evolution-runs-faster-on-short-
timescales-20170314/)

[1] [https://www.quantamagazine.org/missing-mutations-suggest-
a-r...](https://www.quantamagazine.org/missing-mutations-suggest-a-reason-for-
sex-20170713/)

------
c3534l
I'm confused about how the inferences are being made. If genes are found in
older people, okay, so what? That doesn't mean anything. But then the article
says:

> But if that were the case, there would be plenty of such mutations still
> kicking around in the genome.

So does that mean the gene is less common in children than parents? If so,
what does it matter that older people don't have the gene? Why does age factor
into this at all?

------
marcofloriano
* This is not, by itself, evidence of evolution at work. In evolutionary terms, having a long life isn’t as important as having a reproductively fruitful one, with many children who survive into adulthood and birth their own offspring. So harmful mutations that exert their effects after reproductive age could be expected to be ‘neutral’ in the eyes of evolution, and not selected against.

This.

We want to live more (and more). But that's not the main point of life, as
science (and most religions) say.

We are in our best form when we reproduce and give our best to our children
(and family). So they can do the same in the future.

Today's society tries to sell the idea of small families (or no family at all
) and long lives as the best option. But maybe it's not the case.

------
subru
This reminds me of my core mission: sterilize myself or self terminate.

Everything I've experienced and felt since youth indicates that my seed is
unwanted by humanity, and it's clear suicide helps evolution by eliminating
bad genes. I think about suicide constantly and have done so since youth. This
is my brain telling me to help humanity by leaving. Hoping to complete that
mission ASAP.

~~~
jmmcd
I wouldn't necessarily go along with your logic here. If you decide not to
have children for one reason or another you can implement that decision
without suicide. A lot of people have suicidal thoughts at some stages in
their lives, then recover and are glad they didn't take a non-reversible
action.

Anyway, it's too dangerous a topic for you to work things out without a bit of
"peer review". So I strongly recommend to contact a counsellor.

~~~
subru
This isn't occurring st some subset of stages; it's been steady throughout my
entire life. And I've grown more and more cynical with age. It's a decision
that I've long intellectualized.

People who don't survive aren't around anymore to discuss whether they are
satisfied with their decision. Why would I waste my time talking to someone
who intends to talk me out of something that isn't a debate to me? It's a
personal decision.

~~~
magic_beans
Have you considered Buddhism, the entire purpose of which is to learn to
overcome suffering? Here's a summary:
[http://www.bcc.ca/buddhism/fournobletruthsandeightfoldpath.h...](http://www.bcc.ca/buddhism/fournobletruthsandeightfoldpath.html)

------
jlebrech
People are having children later on in life so it would make sense.

------
otakucode
It is odd that longer lifespans would be selected for. Given two otherwise
equivalent populations, the one with the shorter lifespan will come to
dominate.

~~~
24gttghh
This does not seem intuitive to me. Would not having a longer lifespan allow a
subset of a population to better care for itself through social means?

------
meri_dian
This study absolutely does not show that humans are evolving

~~~
pamqzl
Unless the statistical distribution of alleles is _exactly the same_
(unlikely) from one generation to the next then humans would have to be
evolving, wouldn't they?

~~~
gwern
Genetic drift is not usually considered 'evolving' because the variants are
selectively neutral. That's why finding selected variants isn't as simple as
'SNP X is 0.00001% more common in generation 2 than generation 1, case
closed!' \- you are looking for variants which are becoming more/less frequent
than would be plausible under simple drift. Just like an experiment where you
know the effect will never be exactly 0 because of chance imbalances and
random noise.

------
joak
An explanation not explored in the paper: the social pressure to have children
later in life favors people living older.

------
randyrand
we're evolving mostly through sexual selection now as opposed to natural
selection but still some of that too

~~~
sacado2
What's the difference between sexual & natural selection ?

~~~
randyrand
Sexual selection can still happen even if humans become immortal.

Natural selection cannot.

------
LinuxFreedom
You do not even need a scientist to see that there is a massive degeneration
and retardation going on in the US gene pool currently. Influx of foreign
genes was the solution, but now dumbness itself will trigger its own growth
even stronger. If you want a better gene pool for your descendants it is time
to leave US now. Good Luck!

~~~
sctb
This comment is way outside the standards of civility and substantiveness
here. We ban accounts that continue to post like this.

[https://news.ycombinator.com/newsguidelines.html](https://news.ycombinator.com/newsguidelines.html)

