
The evolutionary mystery of gigantic human brains - nnx
https://arstechnica.com/science/2018/08/the-evolutionary-mystery-of-gigantic-human-brains/
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mudil
Human brain is like a peacock tail: it's a product of the sexual selection.
It's too huge of an organ. There seems to be only one way for evolution to
produce an organ that is too huge and too out of proportion to the rest of the
body (as well as compared to the same organ in other species). The mechanism
for such an organ is always sexual selection. It were not sexually selected,
it would not confer enough fitness in itself relative to its high maintenance
costs (a quarter to a fifth of the energy and oxygen consumed by a human).

There is a reason movie stars, famous people, artists, etc are all sex
symbols. Our brain wired to treat them this way. There is a reason we produce
art and music in the first place: they are byproducts of sexual selection.
It's a great topic to learn about!

Some references on this topic:

[https://doi.org/10.1371/journal.pone.0000062](https://doi.org/10.1371/journal.pone.0000062)

[https://en.wikipedia.org/wiki/The_Red_Queen:_Sex_and_the_Evo...](https://en.wikipedia.org/wiki/The_Red_Queen:_Sex_and_the_Evolution_of_Human_Nature)

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YouAreGreat
> Human brain is like a peacock tail

I don't think so. Curious detail about that tail: The females don't have it.

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mudil
You better believe that peacock tail is a sexually selected trait by females
in males.

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greglindahl
And that makes it like the human brain like... ?

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mudil
It makes it an organ of sexual attraction. Just like the brain, an organ of
sexual attraction.

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beloch
I tend to be more convinced by the frugivore argument[1].

i.e. Why do primates that eat fruit tend to have bigger brains than those that
eat leaves? Leaves grow everywhere and one leaf is generally as good as
another. Fruit tends to grow in specific places and ripens at different times.
Primates that had to learn when and where ripe fruit would be tended to need
bigger brains.

The elephant in the room, when it comes to the social brain hypothesis, is
that plenty of herd animals (or school fish) exist in massive groups without
needing terribly big brains to cope. Group size and social complexity seem to
be somewhat independent.

[1][http://www.sciencemag.org/news/2017/03/fruit-eating-
responsi...](http://www.sciencemag.org/news/2017/03/fruit-eating-responsible-
big-brains)

~~~
Theodores
I think that ants are the elephant in the room that you were looking for, they
seem to have exceedingly small brains yet do live in quite large communities
all over the world.

The frugivore argument gets more interesting when you consider how it came to
be that fruit is colour coded in the first place. Why do fruits advertise that
they are ripe to eat by changing colour?

Well, if you are a tree with plans for global domination than producing a few
nuts for squirrels isn't going to cut it. What you really need are primates to
carry your seed far and wide, to get it properly planted with some 'manure'.

So, given the world was once fully monochrome, how did it happen that, as the
trees evolved colour coded fruit the primates evolved colour eyesight?

I blame the Blind Watchmaker. There is no god so therefore colour coded fruit
could not have been specially created just for the primates.

I think that it helps to have vegetarian sympathies to reject the social brain
hypothesis. The idea that bigger brains are needed just to spot what fruit to
eat doesn't cut it if your food is beige coloured. Imaginably we needed those
bigger brains to go on the hunt and to round up woolly mammoths with spears
and stuff.

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stan_rogers
Think birds, not primates, if you want to try to figure out why plants colour-
code seed readiness. Primates kinda suck at dispersal.

~~~
Retric
Birds also have vastly more mobility at lower time energy and risk of
predation.

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vinceguidry
> Even something as simple as moving a group to a new foraging spot is tough,
> Shultz pointed out to Ars.

It doesn't have to be. What makes it difficult is our rational minds. If we
turn them off, finding agreement on things is automatic. It's literally how
herd animals operate.

One thing I take notice of when we go out on team lunches is how the decisions
of which way to cross the street or exactly when to cross are made. One person
takes a tentative step, then the whole group moves, on automatic instinct.
Nobody really cares about when and how to move, so any random impetus gets
picked up on. We all kind of notice it and sometimes it bubbles up to a
conversation where we rib each other, in good fun of course, on those random
impulses that then drive the whole group.

The decision for where to go for lunch is also similarly painless, pain is
introduced when too much thought is given to the decision. We collect ideas
from everyone who has a feeling, then come to a group consensus on where
people want to go. It's only when you forget that there's a instinctual way to
handle group consensus, when you engage your cognitive mind, when you _think_
about what to do, that it becomes difficult.

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natrik
The first step to lead the whole group in some cases is attributable to
leadership (consciously or subconsciously).

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phkahler
They should stop trying to find "the reason" for bigger brains. In evolution
the answer is that everything is in play at once. If socializing requires a
bigger brain, it's in play. If the environment requires a bigger brain, that's
in play. If teaching complex behaviors to the next generation is important,
that's in play. The answer is that all these things probably contributed to
larger brains.

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jpeg_hero
Interesting topic. Perhaps the simpler annswer is that having a bigger brain
is always positive and as (certain) species get more calories it’s better to
“spend” them on brain versus brawn.

All credit to the book “Catching Fire: How Cooking Made Us Human.” We are the
only species that cooks our food and gets the 5x calorie boost from that, and
the only species with the large brain.

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Poc
It's not always positive. Because of our large brain we must give birth before
the child is fully develope and then it take 15-18 year for it to become
adult, before that the child is pretty weak.

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njarboe
One might see this as a positive feed back loop. One thing a large brain is
really valuable for is having ideas about the future you want and then acting
in the world to achieve that goal. The farther in the future your goal is the
better brain one needs. Thus having to raise a child successfully for a long
period of time will help evolve even bigger growing brains and longer
childhoods.

On the other hand, maybe humans are now breaking this restriction as more and
more births are by C-section. I could see a future where most births are that
way (if we don't get artificial wombs first).

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sgt101
Also eating shell fish (high energy + essential oils) and low maturity of
human infants at birth! The second is really interesting, there is a
hypothesis that an early tool used by humans would be a sling for a baby;
enabling immature infants to be managed more easily. Menopauses and
grandmothers come into play as well!

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vfc1
It could be that cooking made the brain bigger. Cooking gave access to a huge
untaped food source that most animals cant eat: starchy vegetables like
tubers.

These are ubiquotous and can be stored in a dry and cold place sometimes for
years, easily a year.

Its a ton of energy that unlike fruit and meat is easily storable for later,
and much easier to catch than a gazelle.

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xyzzyz
When anatomically modern humans first appeared, they weren’t into gathering
and storing food for much later use, because they simply moved too much for it
to make sense. Additionally, the best way many tubers is to just leave them in
the ground.

Agricultural year cycle of planting and harvest, with long periods of storing
the produce is very recent phenomenon in evolutionary history of Homo sapiens,
and not even universal at that — it is northern thing, because it is tied to
grain based agriculture . African and South American peoples often practice
agriculture when they simply leave tubers in the ground and harvest as needed.
It makes the social dynamics much different too, because it makes it less
profitable to raid and steal neighbors food supplies, as they will spoil
relatively quickly when pulled out of the ground, unlike wheat, rye, millets
or rice.

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vfc1
Yes I think so too that storing for months laters at scale started much later.

But it probably also made sense to collect them and store them before they
germinate into a plant at least a few of them, otherwise then we can't eat
them anymore.

Before moving around, they probably grabbed a bunch of them in a simple basket
to have some food later in the day in an unknown place.

Most importantly, tubers are available at a much wider range of latitudes than
tropical fruit. Chimps cant go very far away from the equator due to that,
unlike hominids who have developed the enzimes to digest cooked starch.

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SomewhatLikely
This comes off as little more than reading tea leaves and reveals just how
little we understand the brain.

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puranjay
Understanding the brain seems like such an exercise in recursion. You use the
brain to understand the brain which makes the brain better at understanding
itself, but only according to the knowledge retained by the brain

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lkrubner
I did a similar experiment with myself and my own life, and I think I am
pretty average. Some of you are certainly more social than I am. See "I know
more than 12,000 people. So do you."

[http://www.smashcompany.com/philosophy/i-know-more-
than-1200...](http://www.smashcompany.com/philosophy/i-know-more-
than-12000-people-so-do-you)

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giardini
Human intelligence is a process that runs on a 2-dimensional substrate of
cortex plus the magic of older portions of the brain.

Volume isn't the key to intelligence: big brains are a red herring. Brain size
is poorly correlated with measures of intelligence but the idea sells lots of
books and wastes lots of readers' time. People think it's like Gary Larson's
famous cartoon:

 _" Freeze! ...Okay now...Who's the brains of this outfit?"':_

[http://4.bp.blogspot.com/-BCA1_FLFCxU/UMpbOPEH2xI/AAAAAAAAiO...](http://4.bp.blogspot.com/-BCA1_FLFCxU/UMpbOPEH2xI/AAAAAAAAiOM/fi4TULSkAaM/s1600/far_side.jpg)

There are cases of human hydrocephaly where the cortex has been reduced to a
thin sheet. These people can live normal lives and some have above-average IQ.

 _" Is your brain really necessary? by R Lewin":_

[http://science.sciencemag.org/content/210/4475/1232](http://science.sciencemag.org/content/210/4475/1232)

 _" No Brainer: IQ of 126 and first-class honors degree in mathematics":_

[http://www.rifters.com/crawl/?p=6116](http://www.rifters.com/crawl/?p=6116)

 _" Man with a small brain shows that size isn't everything!":_

[https://www.news-medical.net/news/2007/07/22/27900.aspx](https://www.news-
medical.net/news/2007/07/22/27900.aspx)

 _A Good slide show on hydrocephalus and its effects:

[https://drive.google.com/file/d/0BwI95WRbQAHbMGFjYzQ1YjYtOTN...](https://drive.google.com/file/d/0BwI95WRbQAHbMGFjYzQ1YjYtOTNjMy00ZTQyLWIyZjAtNjZiZWQ0NzMzZWM0/view)

_And don't think the cerebellum is critical either: here’s a woman without a
cerebellum with mostly normal motor function (mild impairments; can still walk
and talk):

[http://www.wired.com/2014/09/24-woman-discovers-born-
without...](http://www.wired.com/2014/09/24-woman-discovers-born-without-key-
brain-region-cerebellum/)

~~~
tomerico
Brain volume does have a (small) correlation with iq in humans.
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2770698/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2770698/)

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hw_penfold
The social brain hypothesis is on a pretty weak footing, since schools of
fish, flocks of birds, herds of ungulates, and swarms of insects all manage to
socialize in largish groups that don't correlate especially well with
disproportionately large brains.

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partycoder
Let's say that by accident, a mutation caused you to have a larger brain.

1) you will need more food to stay healthy because brains are expensive in
terms of energy.

2) you will be pushed to try to get food from as many sources you can but
being bad at recognizing viable food will make you sick.

3) traits tied to good health are favored during sexual selection and
socialization.

4) if you apply your larger brain to augment your collaborative skills, that
helps you in many ways, like better hunting = more food = fewer chances of
conflict/in-fighting

