16 ms·
Why are our brains shrinking?
- deleted 5y ago[deleted]
- kazinator 5y agoBrain size is a bit of a red herring. Elephants have 3X the brain mass compared to humans. Though no dummies, but still. When we think of brain and size, we naturally think of the connection to the intellect. But intellectual activities require patient and slow application of the brain, using external tools like making notes, drawing diagrams and checking one's work for mistakes. Intellectual pursuits are not actually what the brain is good at. If we make an analogy to computing, it's almost like the intellect is a software layer that is bootstrapped on top of the brain in spite of its shortcomings, using some slow, inefficient scripting language. It's not native to the brain. An example of what the brain is natively good at is real-time visual processing and control, like navigating in a complex environment full of obstacles and dangers. You don't have to concentrate your intellect for minutes at a time to tell apart a shape from the background; you just point your eyes at it and it pops out at you instantly and effortlessly, thanks to a power in the brain that you can't even control consciously. (Try as you might, you can't not see the shape.) This is probably why domestication shrinks brains. Perhaps you don't need that much real-time processing in the relatively stable, calm, boring domestic environment.
- aaaaaaaaaaab 5y agoEasy: we've offloaded some of our information storage to external media, i.e. writing.
- chrisco255 5y agoFrom 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 5y agoI definitely move through life seemingly in a mechanical fashion. I suspect in the wild I would be alert, all attention, always anticipating, planning.
- alcover 5y agoin 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.
- necovek 5y agoYou mean bad neighbourhoods like Wall Street in NYC? :D
- chrisco255 5y agoOnly habitual things that you've already learned are done so mechanically. But you've already learned magnitudes more than your ice age ancestors as well as your pre-industrial and pre-information age ancestors. You've flexed parts of your brain and had to use more abstract knowledge than they ever had to. I suspect that some other factor is responsible for the shrinkage. It could just be pure sexual selection. Maybe we find smaller more symmetrical heads to be more attractive and we sexually selected for them over tens of thousands of years. Also could be responsible for domesticated animal brain shrinkage, as we select for more attractive animals. Could it be true that our brains got more complex even as they got smaller or did we legitimately lose some IQ points from the shrinkage?
- dcolkitt 5y agoMaybe 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.
- 5y ago
- bigodbiel 5y agoThe article argues community living, ie domestication hypothesis. Kind of hard to argue when we can today offload brain power used for memorization with a simple google search
- golly_ned 5y ago.
- lame-robot-hoax 5y ago“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 5y agoCome on, give them a chance to make fun of the things the youths enjoy
- Kenji 5y agoProbably because of COVID. Or was it the measures? I always confuse the harm caused by the two.
- algebraically 5y agoBecause 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-wild-domestic.html https://phys.org/news/2018-06-differences-brain-morphology-w...
- Asooka 5y agoHm, then shouldn't people who live in tribal societies as hunter gatherers have bigger brains still? Has anyone studied that?
- algebraically 5y agoI 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/ https://www.nationalgeographic.org/media/genetic-bottleneck/ 2: https://en.m.wikipedia.org/wiki/Toba_catastrophe_theory https://en.m.wikipedia.org/wiki/Toba_catastrophe_theory
- misja111 5y agoIf you read the article you will find that your question is answered in there.
- lumost 5y agoAlternately, big brains are recessive/selected against in all circumstances except those from 6mya to 70kya. We've generally removed most selective pressure at this point, if having big brains is due to a combination of recessive traits we'd expect brain size to start shrinking.
- MaxGanzII 5y agoWhales 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 5y agoMaybe whales are brilliant
- 55873445216111 5y agohttps://youtu.be/h02a2HSB58M https://youtu.be/h02a2HSB58M
- catchmeifyoucan 5y agoJust waiting for something like Moore’s Law where more neurons can fit on a smaller brain
- tommek4077 5y agoJavaScript
- reggieband 5y agoI'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 https://www.youtube.com/watch?v=YJF01_ztxwY
- kadonoishi 5y agoOne point where he talks about domestication starts at 1:54:16 (half a minute earlier he goes over the decrease in brain size): 1. https://youtu.be/YJF01_ztxwY?t=6856 https://youtu.be/YJF01_ztxwY?t=6856
- MisterBastahrd 5y agoWhen'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 5y agoarguably because of too much leetcode practice
- screye 5y agoAssuming 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.
- fleddr 5y agoThe answer has to be Twitter.
- chernevik 5y agoPerhaps it is female (or family) intelligence and impulse control driving the age at which a female paired off and had children. Paleolithic life expectancy was something like 22 to 33, and much of that after very high infant/maternal death rates. With such life expectancies, females would likely be bearing children at ages we today would find positively shocking. Simply surviving childbirth would be a huge selection factor for both mother and child. And girls become fertile well before they are fully developed physically (yes?), and I suppose their ability to survive childbirth presumably increases a lot with each year after menarche until they are fully grown. This might be noticed and communicated culturally. There could certainly be selection advantages to parents and families communicating this to their daughters. On the other hand, adolescents certainly want to have sex at early ages, and our ancestors wouldn't have the same hangups and cultural barriers humans have had for the past several millenia. (Indeed, part of the story here is that developing those hangups is, to some extent, adaptive.). And with shorter lifespans, there would have been some expectation of getting on with it. Sex and mating would have been socially "valid" choices at far earlier ages. If so a girl (/family?) with the intelligence and self-control to 1) notice this and 2) act to postpone mating, even by a year or two, could do a lot to improve a girl's/woman's odds of surviving childbirth and so passing on her genes. If (a big if?) we presume that these characteristics are related to brain size, that might explain it. (If the ability to notice, and communicate, the advantage of waiting were in the _parents_, that would still be be selective for intelligence/control.) As human lifespans extended, pressure to reproduce at an early age would diminish, and it would be easier to create and communicate the cultural norms protecting girls from maternity before they were fully grown. Indeed those norms would become adaptive, as having sex too early would be needlessly dangerous. At which point, _all_ girls would be protected from premature pregnancy, and the selection for intelligence/control would diminish. (Apologies for any ignorance of how the ability to bear children changes after menarche, I have only the standard male knowledge of these things. And for "girl"/"woman" nomenclature issues, the ages in question here are very different than the ones we are today accustomed to.)
- ramblenode 5y ago> Paleolithic life expectancy was something like 22 to 33, and much of that after very high infant/maternal death rates. This is a widespread belief but it is an urban myth. Most of the average mortality from the Paleolithic is weighted downward due to infant and childhood mortality. If you lived past 15 years there was a good chance you would grow old. A 2008 study found that once infant mortality was removed the average life expectancy was 70 to 80 years! [0] > our ancestors wouldn't have the same hangups and cultural barriers humans have had for the past several millenia. Citation needed. Rules over access to women is found across ancient societies and cultures. In patriarchal societies women are a valued good and bargaining chip between men, hence the cross-cultural dowry paid to the father. Promiscuity would have been even more problematic then than today because of small, tight-knit communities where paternity controversy could cause a major social disruption in the clan. [0] https://www.ancient-origins.net/news-evolution-human-origins/life-expectancy-myth-and-why-many-ancient-humans-lived-long-077889 https://www.ancient-origins.net/news-evolution-human-origins...
- goldforever 5y agoHuman brain is shrinking to match the brain size of animals that eat VEGAN/VEGATARIAN diets...LOL
- nitwit005 5y agoWhat's the underlying measurement here? Raw brain size, or ratio of brain to body? > We see an erosion of grey matter, not white matter. Given the lack of an actual brain, I assume this is some sort of assumption based on which part of the brain has changed size?
- owenversteeg 5y agoIt seems like the majority of the comments are not taking into account that this trend began approximately 70,000 years ago - slightly before the various things people here are blaming such as TikTok, Google, writing, Javascript and Twitter. Cutting-edge (heh) technology 70,000 years ago was the stone blade as well as the earliest known primitive art. An interesting guide whenever you're trying to put this kind of thing into context: https://en.wikipedia.org/wiki/Timeline_of_prehistory https://en.wikipedia.org/wiki/Timeline_of_prehistory
- knownjorbist 5y agoI wish I could upvote this more. I would be willing to bet a number of such comments did not even read the article and responding based on impulse with their gripe about modern society du-jour.
- renewiltord 5y agoA thing on HN you will see frequently is that someone will be told that X happened and they’ll explain confidently post hoc why. Occasionally, they will misunderstand this as Y happening and they’ll explain that. In the best universe, they will misunderstand X having happened as Y having happened and explain it even though Y did not happen. The existence of this last characteristic makes me trust post hoc explanations very little. Explanations should make falsifiable predictions. It is easy to fit the facts with a false thesis. Example: https://news.ycombinator.com/item?id=29005765 https://news.ycombinator.com/item?id=29005765
- iratewizard 5y agoThe point system here is meant to help people find insightful comments. There was even a time on this site when it was used like that. But now it's used to show support for opinions you agree with and to find the confident idiots with grand theories of how the world can be modeled.
- algebraically 5y ago
- elihu 5y ago> Yuval Noah Harari, an Israeli historian and a professor at the Hebrew University of Jerusalem, outlines how big brains are not necessarily better brains in his book Sapiens: A Brief History of Humankind. Our brains use around 25% of the calories we eat a day but account for only 2-3% of our body weight (Harari). Interesting that our brains are so resource-intensive. It doesn't seem that surprising that natural selection would favor smaller or more efficient brains in many cases.
- Factorium 5y agoThis is already playing out at a global level: https://www.sciencedirect.com/science/article/abs/pii/S0160289607000244 https://www.sciencedirect.com/science/article/abs/pii/S01602... "There were strong negative correlations found between national IQ and three national indicators of fertility." I think we should look on with worry that there are people with smaller brains that we are now giving unlimited resources to (food, technology, medicine), via aid and welfare programs. The dysgenic potential is immense.
- Kye 5y agoThere are so many problems with this post. * Implying a connection between IQ and brain size * Implying IQ is a measure of a person's worth to society * Implying people below some magic IQ threshold that renders them unworthy are being "given" resources
- lostmsu 5y agoWhile the first one is probably really wrong, the other two are clearly fine. Imagine a unique cat with an IQ of human. Would you say it is more worth to society, than any other cat? Probably so. Is there a magic IQ threshold that renders other cats not as worthy as humans to not be given the same kind of resources? In a way yes, as you would draw a line. Intelligence is what makes humans humans.
- leetcrew 5y ago
- Iv 5y agoThe domestication part makes the most sense in my opinion. However, I only see attempts to explain that genetically. Aren't there environmental factors that can influence this measure?
- syrrim 5y agoAny potential explanation would have to account for the fact that this happened around the world, not only in certain sub-populations. The article isn't clear on whether it began at different times in different places, possibly because the data isn't complete enough. A start date of 70,000 years ago suggests it has something to do with human exodus from africa that occurred around that time. The difficulty is that even southern africans see the change, suggesting that it wasn't particular to the emmigrees. I would therefore propose that some event occurred which pushed humans out of africa, which lead to those that remained having smaller brains, and ultimately lead those that left to the same position. Perhaps that explanation is simply population density. Populations tend to expand geometrically, such that the largest portion of population growth occurs in the latest generations. We also know that all modern humans are descended from a very small set of people, maybe as few as fifty (?). So humans began at that population, slowly expanded across africa for a few tens of thousand of years, started running out of space and were forced to migrate away from africa, then shortly filled up the rest of the earth. Having no where else to escape to, we were forced to deal with increased population density. This lead to lower food availability to support large brains, as well as increased need to reduce aggressive behaviour, achieved via more juvenile brains. Thus, brain sizes reduced across the globe.
- arp242 5y agoAnother question not addressed in the article is whether the shrinkage is linear or happened in spurts (and if so, when these occurred). It's entirely possible, for example, that there was some shrinkage 60-70k years ago, then noting happened for 50k years, and then some more shrinkage in the last 10k years. Another interesting tidbit not mentioned is that you can actually remove a full half of the brain of young children (hemispherectomy) and these people have very normal lives with extremely small or no impact on their brain functions, which is pretty bonkers. This underscores that size isn't everything.
- h0l0cube 5y agoThe article makes reference to this phenomenon being global: > Yuval Harari says that the worst choice in the history of human societies is when humans made the transition from nomadic hunter-gatherers to sedentary farmers. With this, humans became much more susceptible to malnutrition, disease, and famine. Their grain-heavy diets lacked critical nutrients that are essential to proper brain function. But, we see brain shrinkage in the aboriginal people of Australia and South Africans, who never succumbed to agriculture until recent times, and we see the same amount of shrinkage in these populations as well. It's possible as you say that founder effects and reverse migration and interbreeding could account for this, but an alternative theory is that trade emerged as a driving force of human activity, incentivising new behaviours, and so ultimately it was memetics that changed the selection parameters that shrunk brain sizes
- tartoran 5y agoI wonder if it’s religion the true cause/s
- catlikesshrimp 5y agoDon't you ever forget that intelligence is not directly proportional to encephalic mass. Intelligence is related to number of synapses. Brains getting smaller doesn't mean any capacity is lost. Maybe the design was improved, as in metabolicaly less demanding, or developmentaly more reliable. Who knows
- paulpauper 5y agoAlthough our brains were getting bigger progressively, around 70,000 years ago they plateaued, and have been shrinking ever since. John Hawks, an anthropologist at the University of Wisconsin, explains how, over the last 20,000 years alone, human brains have shrunk from 1,500 cubic centimeters (cc) to 1,350 cc, roughly the size of a tennis ball. Except this requires extrapolating brain volume from the skull , which probably inaccurate compared to modern day MRIs. So i would take this claim that brains are shrinking with some skepticism.
- Gatsky 5y agoYes, exactly. I would say the error in measuring brain size over a 70,000 year period is sure to be at least 20%.
- aranchelk 5y ago> we developed elaborate speech. We also have advanced culture I’m surprised there was no speculation involving memes in the article (“meme” as in the original meaning coined by Dawkins). We’re running a complicated and evolved software suite now. The idea that we have less raw computing to do than our bare-brained ancestors might be worth exploring.
- shlurpy 5y agoI didn't see in the article any evidence for this shrinkage correlating with intelligence. It seems plausible that the initial adaptation is just raw, inefficient fast growth (ie, evolution solving intelligence the simplest possible way through raw unorganized volume), and the subsequent shrinkage is accompanied by internal structural improvements and optimization. In other words, like we often do in engineering, first we just throw more more hardware at it to fulfill demands, and then as we optimize algorithmic efficiency the extra hardware becomes unnecessary again.
- DeathArrow 5y agoIt seems that now we use around 10% of the brain power. Maybe we were optimizing for energy consumption? Until the second half of the last century it was hard for the majority of people to find enough food. I would expect that our brain will start to grow slowly if food won't be a problem for a long period. The same way our bodies started to grow once we had enough food.
- T-A 5y ago> It seems that now we use around 10% of the brain power https://en.wikipedia.org/wiki/Ten_percent_of_the_brain_myth https://en.wikipedia.org/wiki/Ten_percent_of_the_brain_myth
- 8eye 5y agoa lot of reasons that people or society won’t accept, for one. confrontation is good. (caveat) if it’s done tactfully
- NoPicklez 5y agoLike others have said, bigger doesn't necessarily mean smarter or more intelligent. I like to think of a scenario comparing the first commercially available computers being the size of rooms, now we have exponentially more computing power in the size of the palm of my hand.
- posed 5y agoReject humanity become monke.
- cryptica 5y agoIt's a well known fact that domestication of wild animals such as wolves causes the head and brain size to shrink over multiple generations. It's probably the same thing happening in humans. It would be interesting to measure the brain volume of politicians and business leaders to see if they follow the same trend as the general population.
- newaccount74 5y agoMy guess is that average individual brain size and intelligence just isn't as important in collaborative society. Once you start sharing knowledge (orally at first, written later), you don't need everyone to figure everything out on their own. There's a also a huge variation in human brain size. [1] suggests almost a factor 2. I don't know if variation was similar 70.000 years ago. [1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262916/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262916/