All of the great apes are incredibly intelligent in comparison to most other animals. The basic roots of our intelligence are probably a common feature to the whole family, but there's no consensus on why it's so advanced in humans. Any paleoanthropologist can rattle off about half a dozen possible explanations, but we honestly don't have enough evidence to really distinguish if, when, and how these were factors at different points in human evolution. Here's a quick attempt at some broad categories, which each have multiple hypotheses within them:
* Because intelligence had advantages for individual selection (e.g. mimetic recall hypothesis)
* Because intelligence had advantages for group selection
* Because intelligence had advantages for sexual selection (spandrel hypotheses often start here)
* Because adapting to rapidly varying ecological conditions required so many adaptations that we crossed some kind of barrier and "fell into" intelligence
* Because intelligence helped with foraging/hunting (exclusive of sociality)
I personally dislike the definitions here-- traits and genetic changes are, by default, unattributed to external pressures. They don't "arise" from the environment, rather the environment selects for traits through survival/reproduction, if applicable.
That means, if a trait is unaffected by the environment, then there's no attribution of why it developed; this is the default state.
I feel often in biology, there's a mindset of figuring out why features developed and that's great for pushing the field but it runs into a limit. Not every trait developed from a environmental pressure.
Technically yes, kind of, but if a feature is truly unaffected by the environment, then there's no particular reason it would get fixed, and you have to make the rather shaky assumption that it became widespread purely by chance. Most features have some cost, and the simplest explanation for that feature being widespread is that it has some counteracting benefit that leads to it being selected for. That's a reasonable first hypothesis, to say the least, which means the "spandrel" hypothesis makes sense as the less common special case.
I don't agree and that's totally fine-- we have millions of gene edits from parent to child and not every change is environment-selected. Certain features can be dominant by the mechanics of genes, not due to selective pressure.
Blood types are an example of this-- they aren't major environmental pressures for why one blood type is more common than others, it mostly comes down to population mechanics.
My belief is that "spandrel" features are less selected for studies because they have a harder burden to prove; there exists no external reason they exist and this must be verified through proof by contradiction. Its a high bar to prove.
Blood types aren't fixed across the population. It's kind of a tricky question which of our points they make a better example for. :D
But also, I guess by "feature" I tend to mean "noticeable feature". You might be more right about that, at least as far as terminology goes. At the bottom end you have a point mutation to a codon for the same amino acid, and then eventually you get something like a slightly different color pattern. Those are probably free.
But as soon as you have to, say, add or increase the size of a physical feature, there's a metabolic cost. And when those features aren't used, that (small!) cost drives them to disappear in relatively short order (for instance, all the convergently legless lizards). That strongly implies that for those, there needs to be a persistent reason for them to keep existing.
Entirely aside, I wonder how long we need to have blood transfusions as part of society before blood type compatibility starts exerting selective pressure.
The jury is still out on exactly how intelligent other hominins were (and the extent of our involvement in their extinction). Regardless, the term human can apply to all of genus Homo and that's the sense that discussions of "human intelligence" typically use.
The burial sites of Homo Naledi suggest they had developed burial rituals and primitive art which would mean non-Sapiens hominids were likely smarter than previously believed
I like that theory although it is depressingly grim ... the top dog species will inherently see any alternative intelligence as a threat and eradicate it. Would definitely make one pause for thought about the wisdom of creating an AGI ...
I think it might be just competition. Human brains are expensive in terms of energy expenditure. So at certain population scales having less energy to expend might be comparative advantage.
And same really goes for other niches we do not even occupy. You need to get something out of those expensive to keep brains.
Since the invention of contraception, intelligence seems maladaptive, although we may have already reached technological escape velocity so it's not clear to me that it'll matter.
There are huge reserves of the population where contraception isn't a thing. There are so many people alive today, that evolving out intelligence is really hard to imagine. Perhaps in some kind of far future science fiction "robots spoonfeeding drooling humanoids" scenario.
Considering human intelligence is very social, I wonder if bias to focus on individual humans leads us to a wrong way of understanding why it arose…
One of my pet theories is that it may be related to vocal cord development[0], where losing certain physiology that allows apes to be louder allowed humans to be more specific, if quieter, with enhanced pitch control and stability offering higher information density communication. This unlocks more complex societal interactions and detailed shared maps. (In Iain McGilchrist’s terms, it let the Emissary—the part of the brain shown to specialize in classification and pattern recognition, the requisite building blocks for efficient communication—to take priority.)
This is an example highlighting how it is not about individual humans “becoming smarter”, evolving larger brains, etc., but rather about humans becoming capable of working together in more sophisticated ways. In fact, human brain shrunk in the last few thousands of years, in concert with growing size of our societies and labour specialization[1], which in turn in no small part is helped by communication density offered by our vocal cords. Really, humans in this way are closer ants[2], where being part of human community is the defining part of our nature.
I've read, from a few separate sources that were not research papers, something similar that claimed the development was a result of existing in semi-aquatic environments such as home on land but swimming for food/safety. I neither agree or disagree (not my field, I don't possess appropriate background/information), but I do think of it when evolution of vocal cords is mentioned.
I don't recall the sources ATM, possibly something out of CoEvolution Quarterly or Bucky Fuller. Again, not research papers.
Semi-aquatic environments make sense if you look at our brains dependency on DHA (seafood is a rich source) and the hypothesis that our fingers get wrinkly in water after a while to improve grip.
Aren't we a lot more evolved for hunting animals on foot? The whole thing with us losing our fur and sweating with the whole body, adaptations to running and throwing stuff, all of this makes us better hunters, but not necessarilly fushermen.
The two go together. Living with water requires control of breathing. Hunting animals on land requires strong endurance and probably also an ability to carry water.
Depending on which factors you weigh most heavily, sociality theories usually fit into either individual or group selection categories. They're sort of the default consensus, but not one that's firm.
Your idea would be what's called a spandrel hypothesis, basically that language (or culture etc) is a side effect of other adaptive traits.
It is not my idea per se, of course… I only gathered (well, it seems sort of obvious) that, given the overwhelmingly social nature of human intelligence, communication with high information throughput is likely the key differentiator between HS and other apes; the rest was ~1 minute of googling.
As to “side effect”, given better communication and consequently cooperation and potential for more complex collectives lead to persistent survival of the species in the environment, they seem like a pretty straightforward evolutionary advantage that would be expected to be naturally selected for in the first place. If anything, chances are in long term the great larynx update is the real side effect, it just happened to be a trait enabling all the above evolutionary advantages.
This highlights just how little we really know, even with decades of fossil, genetic, and behavioral data. What's always struck me is how intelligence might not have been a linear "goal," but more like a byproduct of other traits that just happened to snowball...
Stone tools predate even the oldest suggestions of intentional fire use by at least a million years, so the cooking hypothesis isn't particularly compelling. Elsewhere in this thread I've also discussed how it's not really an explanation either.
The cooking hypothesis is not well known, however, from what I understand, this was when we went from having big guts and average brains to small guts and big brains. The fossil record of primates is far from complete, but roughly speaking, we have been eating cooked food for a million years.
The stone tools that predate this by a few million years reinforce the cooked food hypothesis in this 'chicken or egg' situation.
The only logical pathway is that some genetic mutation or plant-based hallucination allowed for lack of animalistic fear/true context generation within the brain. Understanding that bear/tiger/snake/etc won’t kill you in certain circumstances, means you can expend exponentially less calories and focus on building tools etc. It allows for rapid growth across the species in many areas.
chimpanzees, gorillas, orangutans evolved intelligence too. They are smarter than most other critters in the jungle. Just all not as much as the lineage that leads to humans.
It's actually quite difficult to define human intelligence. Every time we think we find something unique by humans eventually some animal turns up that can do it too. It may be all just a question of degree and how it's used.
From what I've heard, language is unambiguously unique to humans, if you consider grammar an integral part of languages. You can teach chimpanzees hand signs, but they could never make the leap to stringing them together under a coherent rule: something like the difference between "Mom give me cookies" vs "I give mom cookies."
(I'm no expert, so take that with a grain of salt.)
proto-grammers are fairly common. https://en.wikipedia.org/wiki/Alex_(parrot) for example shows that parrots are capable of understanding English word order to some extent.
Unique to modern humans, maybe. But that's only because we outcompeted/killed all of our sibling species that also spoke language. Denisovans likely had language as well.
Starting from what should be considered "writing" to how to identify specific artifacts as abstract words.
Some researchers spend years in the forest studying one animal to isolate one single word they're speaking. Understanding other kind of intelligences is a crazy complex task.
"Why humans evolved intelligence but orangutans did not".
There's a different way to think about this that is closer to how evolution actually works and will make the answer clear.
Our common ancestor (common to orangutans and humans) did evolve intelligence (concurrently with harnessing fire, clothing etc.). Not all of them, but some of them. And they broke off from the group. We now call them humans.
Intelligence was evolved millions of years after the most recent common ancestor. Harnessing fire, clothing, etc. came later still. The lineage that would ultimately give rise to humans split from the chimp/bonobo lineage as the human ancestors adapted to savanna life, likely due to aridification brought on by the formation of the Himalayas.
It's possible that selective pressure towards intelligence was greater for the human lineage than for the others. It's also possible that the evolution of intelligence was equally likely across the different lineages and humans just happened to be the one where the mutation happened. Regardless, once human ancestors filled the niche, it would have been difficult for another lineage to get in on the game.
What definition are you using to say chimps don't have human level intelligence?
By any useful definition, the intelligence of human ancestors very closely resembled that of chimps for about 4 million years after the human and chimp lineages diverged. While it's impossible to say for certain, that's around the time that endocranial volumes started growing consistently beyond the range seen in chimps. That is also around the time of the first evidence of stone tool making.
Substitute orangutans for Australopithecus. That is (one of) the branches that did evolve more intelligence, but didn't survive. I suppose there were lots of such branches, that either merged back into humanity (like the Neanderthals), or died out.
Australopithecus is essentially on the human branch, and likely was still several million years before the development of advanced intelligence. Our common ancestor with Australopithecus was not any more intelligent than a typical Australopithecus, as far as we can tell.
As far as we can tell, no branch developed significantly increased intelligence after splitting off from our own lineage. That's not to say it definitely didn't happen or that our lineage was always the smartest, just that there isn't any evidence demonstrating a qualitative difference which has survived to the present. But it's weird that no such evidence exists.
Conversely different primate groups did independently evolve similar levels of intelligence, like Capuchin monkeys (which are new world primates) developed their intelligence after splitting off from the old world primates some 40 million years ago. Baboons and Macaques likewise each evolved intelligence independent of the great apes. Likewise similar levels (if different specializations) of intelligence have evolved independently outside the primates, such as cetaceans, elephants, and corvids. For cephalopods, which likewise are highly intelligent, their common ancestor with us didn't even have a brain.
I always believed that it was the group that had first mastered fire. Cooking food fundamentally changed human energy budgets. And keeping a fire meant that the group would congregate and form a larger social group, which would then lead to greater communication.
This of course changes the question as to why only/mainly homo erectus developed the capability.
It's the other way round: we are a species because we are the ones that evolved intelligence, which was certainly an enormous difference between intelligent humans and physically identical unintelligent apes.
Ah, I meant on our planet. Of course, we wouldn't wonder if it's evident that there is aliens (other intelligent life from another object) at a similar time as when we evolve this level of intelligence. This would be far before we can make technological means to rule out intelligent life on nearby celestial objects, or someone would probably have come up with the question why we don't talk with (the equivalent of) apes and dolphins and such. The other intelligent life would have to be either among us, or visible from where we live (mountains, ocean surface, idk) with whatever we have for senses (like eyesight good enough to observe structures in orbit that are clearly not natural, as an example)
Intelligence must surely be a cluster of evolved changes, let's say A-Z. Each of those letters must have appeared, and been advantageous on their own (or they wouldn't have persisted).
So why didn't chimps get some of them?
For example, chimps have hands, but do not exhibit anywhere near the dexterity and agility of human hands.
Think less in terms of "this must be inherently better than that" and more in terms of the thermodynamics at play. Dexterous hands probably have some cost. Maybe they aren't as durable as a chimps hands. Maybe they take more calories to run. Maybe they need more brain power dedicated toward the hands and respective energy requirements. I'm not really sure what they may be, but there are usually tradeoffs between any A vs B in an organism.
Now if these costs are indeed less than the fitness advantage of a chimp having more dexterous hands, and that is in biological fitness as in reproductive success not the colloquial 'fitness' as in going to the gym, and that mutation for dexterous hands is present among the breeding population, you will expect to see offspring with that mutation, having higher fitness, to increase in frequency in the population.
There are a lot of potential edge cases to consider as well. Maybe the dexterous hands allele is very close to a very bad allele in chimps, such that through recombination it is likely that these two alleles are inherited together (called linkage). You'd see both these alleles purged from the population over time through purifying selection.
There is the population history aspect to consider. Maybe you don't need dexterous hands if your population is still living in the jungle among plentiful calories like the chimpanzee. Maybe it is more relevant to comparatively more feeble humans that were pushed out of that jungle by physically stronger ape populations into more nutrient poor environments, where suddenly the increased fitness from the advantages dexterous hands might bring now pay for their energy costs.
They did get some of them. Functionally, chimps are pretty smart compared to almost anything but a human. Only if you define intelligence specifically as the gap between humans and chimps (or whatever other reference) can you say chimps didn't get any of the pieces. We can ask why humans have more of the pieces, but that's basically the same question as why any species diverges. So, some inscrutable combination of chance, path dependence, etc
Underrated point wrt intelligence is the extent to which it depends on fine motor control. Whether you're building tools, writing, or speaking a complex language, you need fine motor control to make that possible.
So it's not just brainpower, it's likely a combination of potential brainpower - which many species have/had - and fine motor control, which set up feedback loop that translated a mind/body synergy into practical evolutionary benefits.
There were no chimps back then. We had a shared common ancestor, and subgroups gradually emerged and gradually became different enough that they stopped interbreeding (or were physically separated).
It's an interesting question, but maybe more complex than it appears. We cannot get rid of the cultural passing of information (non-genetic) in humans. If we do, we get feral children [1] (also known as Mowgli in popular culture). But I doubt anyone would seriously want to compare this "pure" intelligence with that of other primates. There is a possible agreement that socialization is not an option for humans but a requirement. Maybe if by some bad luck feral children were grouped together for some time, this might be an approximation, but I'm not sure. Overall, using computers as an analogy, it's like humans are only functional after the software installation following the first power-on, which is more or less required for normal activity.
This may not be entirely accurate. Feral children are those that do not have interaction with other humans.
If you had a bunch of human children together and provided them sustenance and all that without adult interaction they might still develop normally and form their own language and means of communication with each other.
We don’t know for sure because such an experiment would be horrible and extremely immoral. However I do remember reading a while back that a similar situation happened where a bunch of deaf children in a an environment without much adult interaction did manage to create their own sign language to communicate with each other.
So it seems the feral child phenomena might be due to the fact that the child is alone rather than simply due to the child not having adult interaction.
> where a bunch of deaf children in a an environment without much adult interaction did manage to create their own sign language
You probably had Nicaraguan Sign Language [1] in mind. I think it’s a good example of the human brain’s ability to invent something and acquire knowledge easily. What I tried to show with my comment is that when human intelligence is discussed, it’s easy to refer to all instances of human achievements around us, but they are essentially accumulated cultural knowledge. Because of this, we tend to overestimate our intelligence, at least when comparing an individual human with an individual primate of another kind.
So, it’s also interesting why humans are probably unique in this ability to pass on and accumulate information, while other apes (and crows) limit this to skills like retrieving ants with sticks and breaking shells with stones.
I have no expertise in the field whatsoever but can't help but wonder if it is at all related to our consumption of cooked foods. At the very least it reduces the incidence of parasites but I am sure there are myriad benefits beyond treating foods for longevity through methods like smoking.
I have zero expertise either, but I find this field fascinating. Cooking makes it easier to chew so we can devote less of our skulls to chewing muscles. At birth our skulls are barely small enough to fit through the birth canal in one orientation, and one of the prerequisites for a baby to be born is that it’s facing head down and shoulders rotated into that orientation. Maybe cooking is beneficial because it allowed us to have a bigger braincase but also it gave us access to more nutrients from the same food.
Humans are a protected species, carefully raised and nurtured by higher organisms that are hundred thousand times larger than us (in terms of space and time). The earth and solar system is just a vivarium of galactic scale. Several "glass wall" mechanisms were placed to ensure we are separated from the rest of the universe, like the oort cloud.
Somewhere out there in the universe are humans living freely outside the glass wall.
Playing with this outlandish thought further, the idea that earth is an enclosure for research or preservation explains why the solar system is configured the way it is and why tiny adjustments could render it an inhabitable wasteland.
As time goes on, the glass walls tend to age and occasionally the "cracks" allows external lifeforms (aliens) to slip past the protection layer, much like how insects or parasites would occasionally slip past any opening.
With this in mind, there would be two types of aliens/visitors to our enclosure: (1) lifeforms that are similar to humans in terms of size and biological complexity but more technologically advanced and (2) our protectors who are incomprehensibly larger and more complex than any life on earth. This isn't as outlandish as it seems to be considering there are stars that are million times larger than our own sun.
This sheer difference in scale might as well make the protectors exist in a different dimension. This explains why people would say that aliens were here all this time, but from another dimension. Technically they are here, but more accurately to say the protectors surround us.
Occasionally protectors would step in to prevent mankind from destroying their own enclosure, much like a terrarium owner would reach into the enclosure to remove unwanted organisms. Frequent unidentified sightings on nuclear sites is the protectors' way of peeking and reaching a "hand".
It remains to be seen if humanity would one day evolve to outgrow the enclosure.
Is an individual human raised alone significantly smarter than a chimp?
How much of the intelligence gap is culture and communication that lets us educate ourselves and compound knowledge vs biology? Homo lived for thousands and thousands of years with the same level of development as other apes
Since it is impossible to instill human culture into a chimp (and scientists certainly have tried) there must be some important biological differences between people and chimps.
That question is analogous to asking why did some fish grow legs and become mammals.
The answer is mutations sometimes specific members of a group will gain a mutation that will overtime cause that group to split off away from the ancestor group. It’s all a matter of chance evolution doesn’t have a direction.
Multiple lines of mammals have independently evolved back into being marine life. Whales, seals and manatees do not have a common ancestor, for example.
A curious-er question to me would be how did cephalopods (octopuses, cuttlefish) develop sophisticated intelligence a few hundred million years before ‘we’ did separately from us?
And they still are alongside us right now. Which to me is fascinating.
The other apes are intelligent enough for their niche. At some point in humanity's past, the environment was harsh enough that the less intelligent ones died.
Because we are farther way on the evolutionary tree then is commonly thought, there is a tree of common ancestors going much further back (5 million or more years) that links humans with monkeys
Evolution doesn't have end goals like building the most powerful computer possible. If caloric excesses are a factor, it's because there was some other selective pressure that made use of the energy to support more neurons. But even then, more hardware isn't the same thing as more intelligence. Elephants and whales have bigger brains than we do. Shrews and birds have a higher brain/body mass ratio. None of them are intelligent to the degree humans are. An explanation for human intelligence has to explain us, not just our brain mass.
Sperm whales may have more massive brains, but they have fewer cortical neurons total, and of course a much smaller brain to body mass ratio.
But more importantly for this conversation, our brains use up a staggering 20-25% of our resting metabolic needs. A whale brain uses something like 3%.
For us to be able to devote 20% of our calories to our brains, we simply needed to have a huge excess in the number of calories we had available. This is why the cooking hypothesis makes sense. Once we were smart enough to get lots of excess calories, that opened the door to this new fitness landscape of organisms that could devote a ridiculous proportion of their food to their brains. It wasn't that we gave up something else, it's that this wasn't even a possibility before.
I think this is actually an easy question to answer because you’ve accidentally preselected your demographics.
Imagine this: among primates, there is an even distribution of species of differing levels of intelligence. All the primates who became intelligent have similar evolution paths because intelligence defines their evolution path (opposable thumbs, large heads, standing upright, etc.) Then because they all have similar evolution paths we put all those into the genus “Homo.” Each of species of the genus Homo eventually either breeds with each other or genocides one another until there are only the Homo Sapiens left.
So with an even distribution of intelligence among all primates, it’s logical that, given enough time, all that is left are primates of sufficient intelligence enough to breed with each other or be genocided until there is only one species, or many species of primates who weren’t intelligent enough.
This is my guess (I’m not a biologist or ancient historian or anything)
I can extrapolate based on my toddler that a modern human dumped in the wild would invent language. He has made several phonemes that aren’t in the language we speak at home. And he’s clever enough that even though he’s never seen us stand on furniture, he still climbs drawers and chairs if there’s something he wants that’s out of reach. I think that tool use and language are borne of some innate drive that’s accelerated by culture.
> He has made several phonemes that aren’t in the language we speak at home.
No I mean absolutely zero contact with or help from modern (say since the last 10,000 years) human civilization.
I mean literally giving birth in a forest and then raising the baby there without ever speaking a word around it or showing it any tools etc.
(this assumes that it will survive to 1-2 years old without any fatal sickness etc. but let's say that the mother/parents will get just enough "outside" help to make sure it does, but the baby itself is not to come in contact with any tech or language)
I'm pretty sure there were children where the parents basically locked them in cages or chained them to a post in the basement, where they had almost no social contact, etc. And in these cases they were considered effectively mentally disabled by the time they were rescued.
That’s different. He’s not saying to totally isolate the child, but that the child is born to modern humans without any language or culture or knowledge but who live in a wilderness. So not a place of deprivation but a place of danger and exploration. I would argue that kids are wired to explore, and that the parents would do their best to protect the child. It’s kind of a useless thought experiment because our lineages stretch back unbroken to the beginning of life, and that includes culture and transmitted knowledge.
Given that the future human is different than you are today, they could ask you the same questions. How does it FEEL for you to communicate worldwide with an HN post, but not yet have the ability to (insert advanced capability here).
Every one of our evolutionary ancestors was the best human yet, just like we are.
> Given that the future human is different than you are today, they could ask you the same questions. How does it FEEL for you to communicate worldwide..
No no no, I don't mean going from already intelligent/sentient/sapient to MORE intelligent….
I mean, going from the levels of intelligence/awareness we see in insects → fish → chickens and cattle → monkeys/apes → what we consider "actual" intelligence as seen in humans.
Evolution of anything is obviously not some simple boolean switch: It's not like one day you're a full fish and the next day you give birth to an amphibian with legs.
But how would the gradual evolution of intelligence look and feel like?
Going from what we consider animals to be, to having awareness and introspective thoughts and future planning?
Is it like, do you have just 1 thought per day at first,
or can only count up to 3 for a few thousand years,
only plan for up to 1 day ahead, and remember that plan for only a few hours…
And when do all the clearly self-destructive things kick in, that we Modern Humans™ do that obviously harm individuals and the species? :)
I guess I see it as a continuum. My cats are clearly not as smart as a human, but they remember and they have independent thoughts. Presumably they wouldn’t feel inadequate compared to a human, since they get everything they could possibly want and we do the work. But it’s highly unlikely that they are smart enough to have that self-reflective thought.
Humans have the gift of understanding, but our lives are filled with things we either don’t really understand or that we have an illusion of understanding. Of course, we wonder “why does evil exist?” whereas cats wonder “when is dinnertime?”
All apes are intelligent. Studies have shown that their causal reasoning is almost on par with humans. What they seem to lack is language for communicating sophisticated concepts and persisting them across generations.
Thank you. One person. One person is able to question the narrative of human intelligence and arrive at the essential distinction. Maybe a reflexive habit of mind that seeks to find differences between the human and the other and is incapable of seeing the other in the human.
