[HN Gopher] Why are our brains shrinking?
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Why are our brains shrinking?
Author : kodah
Score : 43 points
Date : 2021-10-28 21:06 UTC (1 hours ago)
(HTM) web link (usfblogs.usfca.edu)
(TXT) w3m dump (usfblogs.usfca.edu)
| screye wrote:
| Assuming it has to do with evolution, it would mean that there
| are clear breeding preferences that where folks with 'smaller
| brain' mutations' are likely to reproduce at higher rates than
| your average person. ( Idiocracy Theory ?)
|
| Is it possible that there is long term development of emergent
| traits in a species, through a process that is not evolution ?
|
| I don't buy the domestication hypothesis, because I see no proof
| that aggression has been disincentivized over what we know about
| ancient human history. There might be unintended consequences,
| where those who don't go to war are more likely to live and
| therefore reproduce, leading to propagation of non warring = low-
| aggression genes.
|
| Lastly:
|
| > This may mean that smaller brains are being naturally selected
| for. Of course, this hypothesis relies heavily on premises that
| are both not confirmed and highly controversial.
|
| When the only reason to reject a hypothesis, is that it is
| controversial, I am inclined to assign it a higher likelihood.
| reggieband wrote:
| I'm sure some are aware but in case you are not, Lex Friedman
| podcast recently had an episode with Richard Wrangham [1] where
| they discuss this. Wrangham is a primatologist that studied
| alongside Jane Goodall. His theory suggests human's show signs
| similar to what we see in other species that have been
| domesticated. This includes smaller face/jaws and smaller brains.
|
| 1. https://www.youtube.com/watch?v=YJF01_ztxwY
| MisterBastahrd wrote:
| When's the last time you had to use your brain to survive? Wild
| animals do it all the time. Domesticated animals just wait for
| their next meal.
| throwaway879080 wrote:
| arguably because of too much leetcode practice
| MaxGanzII wrote:
| Whales have brains which physically are much, much larger than a
| human brain; size does not directly equate to intelligence. Note
| also brains are extremely expensive, physiologically, to
| maintain. It may simply be we are evolving to be more efficient.
| FredPret wrote:
| Maybe whales are brilliant
| 55873445216111 wrote:
| https://youtu.be/h02a2HSB58M
| catchmeifyoucan wrote:
| Just waiting for something like Moore's Law where more neurons
| can fit on a smaller brain
| fleddr wrote:
| The answer has to be Twitter.
| golly_ned wrote:
| .
| lame-robot-hoax wrote:
| "Although our brains were getting bigger progressively, around
| 70,000 years ago they plateaued, and have been shrinking ever
| since."
|
| TIL TikTok existed 70,000 years ago.
| diag wrote:
| Come on, give them a chance to make fun of the things the
| youths enjoy
| Kenji wrote:
| Probably because of COVID. Or was it the measures? I always
| confuse the harm caused by the two.
| algebraically wrote:
| Because we are being domesticated. Domesticated animals are all
| dumber than their wild counterparts. Every wild animal that ends
| up being domesticated ends up with a smaller brain. I should
| rephrase and maybe say that this doesn't necessarily mean the
| animals get dumber but they definitely change in the process of
| domestication and a smaller brain is one of those adaptations.
| [1]
|
| > The reduced amount of white matter suggests that domestic
| rabbits have a compromised information processing possibly
| explaining why they are more slow reacting and phlegmatic than
| their wild counterparts.
|
| 1: https://phys.org/news/2018-06-differences-brain-
| morphology-w...
| amelius wrote:
| Yes, people give away their private data for small
| conveniences, much like how pets give away their natural lives
| in wilderness for a guaranteed meal and a warm house.
| iamstupidsimple wrote:
| What a bizarre comparison. Any animal would make the same
| 'choice'.
| FormerBandmate wrote:
| 70,000 years ago people were running around in groups of
| 50-200 people killing mammoths. Private data has nothing to
| do with this, that's only happened in the past 20 years and
| there isn't a generation that has lived their whole lives
| with smartphones that are adults yet. We have no idea what
| effect they'll have on evolution
| FormerBandmate wrote:
| Domesticated by whom? How?
| [deleted]
| lovecg wrote:
| By ourselves and the structures we created. Agriculture, etc.
| algebraically wrote:
| It's possible for an animal to domesticate itself. This is
| one of the theories for how wolves were domesticated. It's
| not that humans did anything special to domesticate them but
| that wolves started hanging around humans and eating the
| scraps that were left over at campfires and other human
| habitation sites. Eventually the less fearful and tame wolves
| became human companions. Once people realized they could hang
| out with wolves they started actively breeding more tamer
| variants.
|
| The same is true for humans. The process is obviously
| slightly more complicated because unlike wolves people have
| more influence on their environment but it's undeniable that
| humans are now domestic animals. No modern human can survive
| in the wilderness and this process is accelerating. We are
| now, for all intents and purposes, dependent on mechanical
| tools and technology for our continued existence. Feeding 8B
| people is impossible without industrial farming and
| agricultural techniques, e.g. Haber-Bosch. [1]
|
| 1: https://www.sciencedirect.com/topics/engineering/haber-
| bosch...
| tomjen3 wrote:
| I did some research into this a couple years ago. There is
| an interesting theory that we didn't domesticate wolves,
| but that wolves domesticated us. For one, wolves naturally
| are very intelligent and pack hunters, so they could have
| used humans as a hunting partner. For another point, we
| domesticated wolves way before anything else (atleast 20000
| years ago) and that makes no sense since every other animal
| we domesticated (goat, horse, chicken, etc) will eat pretty
| much anything and is only of very limited threat to us,
| whereas wolves are carnivores (very expensive to maintain)
| and extremely dangerous.
|
| However, if wolves domesticated us as hunting partners,
| then this starts to make a lot more sense. We didn't need
| to first learn domestication on easier species, the danger
| was limited and our hunting would be so much more effective
| that it was worth the premium.
|
| It also explains why we have the concept of werewolf and
| why some people have been charged with turning into wolves
| to be successful in hunting, but never any other animal
| (there are no cases of ware eagles/falcons). There is
| something primeval deep inside us that associates wolves
| with successful hunters.
|
| I find the theory neat, I am not convinced it is true.
| algebraically wrote:
| Ya, I also don't know if it's true or not. I was just
| making the point that an animal can domesticate itself by
| changing its environment and then adapting to the new
| environment in a way that ends up being essentially a
| self imposed domestication process.
| amelius wrote:
| Ourselves. The conveniences we strive for.
| scoofy wrote:
| Whoa... whoa... let's unpack all the intense presuppositions
| you're packing in here:
|
| "Domestication" is just a word for a natural evolutionary
| processes in a symbiotic system. The concept that
| "domestication" is like, actually a thing apart from evolution
| is a vastly more difficult idea to parse than it appears on
| it's face.
|
| >Domesticated animals are all dumber than their wild
| counterparts.
|
| I mean... again... there are so many things to unpack here.
| What do we mean by "dumb" and which parts of the brain are
| being used, and how their size relates to their usefulness. I
| think it would be extremely difficult to argue any of these
| claims on their face beyond: small brain -> less brain
| function, which is extremely spurious.
|
| Homo neanderthalensis had notably larger brains than us, yet
| they did not survive. Hardly an argument for the idea of
| greater intelligence -> greater brain size. AFAIK, specific
| areas in the prefrontal cortex is the primary point of interest
| when it comes to intelligence, and it's a relatively small
| section of the brain compared, say, to the visual cortex.
|
| https://www.discovermagazine.com/planet-earth/neanderthal-br...
|
| Finally... the most absurd of all the ideas packed in here is
| that natural selection for smaller brain size would even be a
| thing. Human mating is openly available for study, I see
| little-to-no argument for this being plausible beyond some sort
| of idiocracy world (is this the domestication thesis you hold?
| I see in the article they are treated separately), which is
| genuinely problematic. Possibly that certain types of brain
| sizes are predisposed to certain behavioral patterns. However,
| the idea that there is even a single evolutionary pattern for
| billions of humans is pretty ridiculous. We don't have
| evolutionary islands like other animals do.
| akomtu wrote:
| Domestic animals have safe, boring and predictable
| environment. It's expected that they'd simplify their brain -
| the organ that consumes so much energy. If domesticated
| animals started playing chess, that would be a different
| story, but they spend their life mindlessly walking between a
| food dispenser and a litter box, taking naps in between.
| scoofy wrote:
| >they'd simplify their brain
|
| This is not how evolution works! They are not in control of
| their breeding. Evolution is not some intelligent agent
| with goals. It is like a river, responding to to the path
| of least resistance in reproduction.
|
| Intelligence and/or brain size not a dominant evolutionary
| factor unless they are specifically bread for intelligence
| and/or brain size. Domesticated animal's dominant
| evolutionary qualities have nothing to do with the animal
| preferences for mating, thus brain size in fairly
| arbitrary, and we should suspect it to be some sort of
| drift, rather than rationally getting smaller.
| algebraically wrote:
| This is a good point but it does seem like people
| consistently select for less intelligence because less
| intelligent animals are more tame and easier to control.
| cogman10 wrote:
| I think the only thing I really quibble a bit with is the
| description of "dumber".
|
| Our "domestication" has historically been more that we've gone
| from a generalist species to a specialist society. With that,
| things that were previously probably a boon for survival and
| reproduction become less so (For example, quick reaction times
| don't matter so much when you have a city wall to keep out
| predators and a backup hunting party).
|
| My assumption is that what we've lost is more our brain matter
| used to sleep in trees and wake up/run from predators at all
| hours of the night. Stuff that's less important when you have
| night watchman, fires, and shelter.
|
| It's similar to how dolphins have huge brains, but most of that
| is dedicated to sound processing. If dolphins learned how to
| make huts, farm fish, and fight off predators I'd imagine the
| part of their brain dedicated to processing sound would start
| to shrink as there isn't the evolutionary pressure to keep it
| around.
|
| Sort of like how humans might be evolving towards color
| blindness because being able to tell the difference between red
| and green doesn't necessarily increase our ability to have
| children. That might lead to weird changes in our eyes and
| brains that could shrink them but wouldn't necessarily mean
| those humans are any dumber than their predecessors.
| matheusmoreira wrote:
| Sounds like we need to take control of this evolutionary
| process and start engineering it. Just because we are no
| longer required to use these abilities on a daily basis
| doesn't mean we don't want them. Evolution can go to hell
| with its "pressures", humanity is supposed to get better over
| time, not worse.
| algebraically wrote:
| Good point.
| Asooka wrote:
| Hm, then shouldn't people who live in tribal societies as
| hunter gatherers have bigger brains still? Has anyone studied
| that?
| algebraically wrote:
| I don't know. That's a good question but most modern humans
| are essentially clones so I don't think there is going to be
| much difference. [1][2]
|
| 1: https://www.nationalgeographic.org/media/genetic-
| bottleneck/
|
| 2: https://en.m.wikipedia.org/wiki/Toba_catastrophe_theory
| lordnacho wrote:
| Why is there evolutionary pressure for the brain to shrink? We
| seem to have enough calories to feed our brains, and we're not
| beholden to some master species that needs to economize.
| playpause wrote:
| "Use it or lose it" applies in evolution, because of energy
| usage, but also because of complexity. More features means
| more things to go wrong, more options for cancers, etc.
| rackjack wrote:
| The brain itself is the evolutionary pressure. It is often
| repeated that the brain takes ~20% of our body's energy
| despite being ~2% of our body's mass. If there is no need to
| have a brain so large (due to a lack of predators) it is
| beneficial to shrink it.
| dymk wrote:
| It's beneficial to lower the brain's calorie intake it if
| it results in higher reproductive fitness. But like GP
| said, we have plenty of calories, more than we've had
| compared to the entire history of humanity. So it doesn't
| naturally follow that lower calorie brains are higher
| fitness in 2021.
| Robotbeat wrote:
| Beneficial how? Reduction in calories? We tend to have
| diseases of excess calories in the developed world now. If
| anything, the greater brain metabolism may actually help by
| burning some of those excess calories off...
| algebraically wrote:
| Because we no longer need to run away from predators and
| process information at the same rate we'd need to in a more
| wild enviornment. The survival pressures of our ancestral
| environment are no longer relevant. We've essentially
| destroyed and driven to extinction every other predator on
| the planet and now the only selective pressure is adaptation
| to the human created environment which is much nicer and
| simpler than the wilderness we came from. Simpler and safer
| environments make simpler brains and that's my best guess at
| why our brains are shrinking but I'm just an armchair
| scientist so it's better to ask the experts. The only
| remaining selective pressure is basically human predators,
| a.k.a. sociopaths.
| jacquesm wrote:
| > and process information at the same rate we'd need to in
| a more wild enviornment
|
| If anything that rate of processing has gone up, not down.
| algebraically wrote:
| And most of it has been offloaded to computers (big data,
| deep learning, etc). I don't think we're going to have
| "mentats" any time soon.
| jacquesm wrote:
| You have this backwards. We are dealing with orders of
| magnitude more information than we did in ancient times,
| and we are required to remember a good chunk of it and to
| be able to recall and use it at a moments notice.
|
| Computers are a big factor in generating all of that
| information, even if they help process some of it the net
| effect is a huge surplus.
| algebraically wrote:
| I don't think I have it backwards. I don't remember
| anything or know much about the world in general terms. I
| just know and remember enough key phrases for google to
| give me the answers when I need them. [1]
|
| 1: https://www.psychologytoday.com/intl/blog/the-
| athletes-way/2...
| GDC7 wrote:
| > We are dealing with orders of magnitude more
| information than we did in ancient times, and we are
| required to remember a good chunk of it and to be able to
| recall and use it at a moments notice.
|
| Surely you mean required, meaning you could end up
| embarassing yourself in front of your coworkers if you
| aren't able to recall that particular bit of information.
|
| It's very different from REQUIRED, meaning that if you
| take a left turn instead of a right turn while running
| away from a predator you end up in a canyon... or the
| predator eats you because you have no way to escape...or
| both.
| kkoncevicius wrote:
| This is discussed in the article as one of the possibilities.
| algebraically wrote:
| Makes sense.
| aaaaaaaaaaab wrote:
| Easy: we've offloaded some of our information storage to external
| media, i.e. writing.
| chrisco255 wrote:
| From the article it indicates this shrinkage began 70K years
| ago, or 65K years before writing. In addition, vast majority of
| the population didn't know how to read or write until 100-150
| years ago.
| JKCalhoun wrote:
| I definitely move through life seemingly in a mechanical
| fashion. I suspect in the wild I would be alert, all
| attention, always anticipating, planning.
| alcover wrote:
| in the wild I would be alert
|
| I am when I hike alone. Not super alert - since there are
| few dangerous animals in my country - but alert still.
|
| Also, you are very alert when you walk in bad
| neighbourhoods.
| dcolkitt wrote:
| Maybe it's just language in general. If I'm in a tribe with
| 100 people, and we all know to talk, not everyone needs to
| remember every single thing you might ever need. If you
| forget something, you can ask around, and probably someone
| remembers.
| Shorel wrote:
| But memorizing oral history surely was a thing back there.
|
| A single narrative for all things is probably simpler than
| having to figure everything out every lifetime, like
| octopuses do.
| tommek4077 wrote:
| JavaScript
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