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!
Couldn't our proclivity to kill one another also have a hand in it? In some societies the murder rate for males was up to 40%, surely that sort of pressure must select for, among other things, cunning?
Chimpanzees kill one another and they’re just extraordinarily strong, and haven’t evolved human level intelligence because of it. Being able to rip off someone’s arms is more useful than being clever of violence were purely the answer.
The Macedonians took over the Greeks, who were more “clever” than the Macedonians. The Mongols took over China, but the Chinese are more “clever”. Scythians didn’t even have writing.
So, I think you can kill a whole lot of people without being the most cunning.
Rather there's a fix point: The brain is adapt at increasing its size. That's what everything does: Growing. The brain is just especially good at it.
The advantage also manifests in the "schema of childlike characteristics" (Kindchenschema) which includes a big head. So it's evidently also important for affection on a different level: child care and protection.
There are pretty bold statements in your comment, that may be countered with a lack of constraints on the growth. Intelligence affords fitness in myriads of ways, of course.
This. Kept scrolling down, wondering when I was going to see this comment. Related to language, too. You don't need complex language in groups of social primates for survival. When you see it in nature, like in birds and whales, it's about finding a mate.
>When you see it in nature, like in birds and whales, it's about finding a mate.
Not exactly, at least for whales. The humpback whale song's function has not been fully understood. The initial hypothesis that it is a vocal display for females has not been supported, since females do not approach singing whales, and whales sing all over the place, not just at the breeding grounds. So the function of a humpback song might not be solely to find a mate, or might not be related to reproduction at all.
Furthermore, you do need a complex communication system for complex social groups. For example, there are two bottlenose dolphin ecotypes:coastal and offshore. Coastal ecotype is a small fission-fusion society and we see a somewhat simple vocal repertoire. The offshore ecotype lives in big groups and they have very complex vocal repertoire. The bottom line is, at least for cetaceans, we still do not have enough data and understanding to realy argue about the complexity of their communication system one way or another. But it definitely goes beyond of just being "about finding a mate"
This is the best comment on this subject, yet somehow this comment is at the bottom of the page. This is an example of all the things I nowadays find frustrating with Hacker News. The best comments don't get upvoted any more.
I didn't downvote it, but there are a number of things that made me sigh, so this may partly clarify other people's sentiments if they happen to be similar:
-The tone of the comment is very matter-of-fact and peremptory, as if that explanation was obviously the only one and not just one among the dozens that have been put forward by the community so far, all having more solid support.
-The lack of proper sourcing. A plos one and an evopsych pop sci book do not count as proper sourcing.
-The expression "brains are wired". At least they didn't say "hardcoded", but still. It's as lousy as people calling DNA source code.
-The quasi-Freudian mindset some people demonstrate by seeking to placate sexual selection onto everything that arises through evolution.
-The very loose attempt to apply this argument to present-day cultural phenomena. I find it too easy.
-Basically anything involving evopsychy explanations for anything is very likely to be sigh-worthy.
Before some of you come out of the woodwork (yes, you) and jump at the argument with more plos one citations and retorts from whoever is the flavorful evopsych specialist of the month: yes, I am aware sexual selection is a thing, I partly work on it. Yes, I know evopsych shouldn't be dismissed off-hand. No, I am still not willing to have the discussion you're about to engage me with. To be honest I don't know many scientists who are, it just feels fruitless for us.
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.
>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.
Herds are a less complicated form of socialization. By contrast humans need to keep track of dozens of interpersonal relationships as a matter of personal survival. If you aren't paying attention, even the biggest toughest strongest man can be undone by 3 or 4 of his rivals banding together and attacking him as one. I'm reminded of one instance I read about several low status chimps all pouncing on an alpha who'd gotten too complacent and castrating him with their teeth, thereby ensuring he was permanently out of the running for leadership. Under such conditions, being clever is not just a nice-to-have - it is a matter of survival.
The frugivore arguement might be totally valid too. As does the "natural" defense arguement - animals that have natural defenses like shells, quills, or other bodily forms of armor and defense tend to be less intelligent than creatures that lack such features. So it stands to reason that humans, as the species with the least equipped with natural defenses, would also be the cleverest of the bunch.
But ultimately we just don't know. All we have is raw speculation.
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.
"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."
I don't think this is a valid point. From the point of view of the genes, is not an ant colony one big organism?
"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."
A bigger brain is very energetically demanding and fruits are a lot energetic than leaves. Maybe, only primates that eat fruit can afford big brains?
> 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.
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.
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.
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.
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).
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!
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.
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.
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.
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
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."
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?"':
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.
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):
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.
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
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://en.wikipedia.org/wiki/The_Red_Queen:_Sex_and_the_Evo...