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)
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.
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.
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.
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.
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 ...
Stone tools predate even the oldest suggestions of intentional fire use by at least a million years, so the cooking hypothesis isn't a particularly compelling explanation.
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.)
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.
"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.
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.
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.
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.
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
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
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.
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.
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.
All the evidence we have points to the vast, vast majority (>90%) of non-african human ancestry originating from hominin populations that were in Africa around 60-80k years ago, and were anatomically modern about 300k years ago. This article is about an ancestral clade of archaic hominins that contributed around 2% of modern non-african ancestry globally, that we've known about for years.
OOA (with minor admixture) is the consensus position for a lot of excellent reasons.
It is also the consensus position for a lot of bad reasons though.
There is an assumption that belief in, or even reasonable agnosticism towards, any other theory can only be motivated by racism.
There are many people that believe OOA because they want to believe it, because they want to believe we are all more similar than we are different, etc.
Multiregional hypotheses are perfectly plausible. We have very limited information one way or another. Out of Africa may be more likely but it is far from certain.
Just to be clear about what the term multiregionalism means, it's an argument that there's anatomical continuity between archaic hominin populations around afroeurasia and modern human populations. That is, anatomical modernity didn't evolve once in Africa, but multiple times all over the world in populations that are still extant today. A multiregional hypothesis might say that modern Chinese people evolved from archaic populations in Asia.
This is completely and unequivocally rejected by the genetic evidence. The evidence is so absolutely overwhelming that even fucking Wolpoff came around and now says:
It is broadly agreed that all recent/living human populations ultimately descend from Africans.
Now, if you mean something completely different to the commonly understood definition of multiregionalism, I'm willing to hear it.
There are many people that believe OOA because they want to believe it
But, also, There are many people that [do not] believe OOA because they [do not] want to believe it.
That's why we look at genetic evidence, to eliminate nonsense. That evidence strongly points to chimps, gorillas, humans etc all coming from the same place.
If it makes you feels better, think of it this way:
we don't believe OOA because the evidence says we're related to blacks. We believe it because the evidence says we're pretty much hairless apes. (And a lot of us aren't even hairless!)
theres actually almost zero clarity around the common ancestor between apes and humans, and a lot of speculation that the common ancestor lived 6-8 million years ago.
We know there were indigenous folks here in Australia ~50K years ago, and we know that we didn't evolve in Australia, so any origination must be further back than that.
You are completely wrong. Out of Africa is correct. Out of Asia is incorrect, and is outdated sino propaganda. Even the modern Chinese state admits that DNA evidence pretty conclusively points to out of Africa.
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)
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.
[0] https://www.theguardian.com/science/2022/aug/11/how-quirk-of...
[1] https://www.bbc.com/future/article/20240517-the-human-brain-...
[2] Ants that farm and have stronger division of labour have smaller brains: https://www.smithsonianmag.com/science-nature/how-ants-becam...
Your idea would be what's called a spandrel hypothesis, basically that language (or culture etc) is a side effect of other adaptive traits.
And same really goes for other niches we do not even occupy. You need to get something out of those expensive to keep brains.
Survival of the fittest never includes the gene impacts plants and fungi can force onto creatures.
Also cyclical 12kyr catastrophic events leading to small condensation of species under stress.
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.
(I'm no expert, so take that with a grain of salt.)
As does house finches: https://royalsocietypublishing.org/doi/full/10.1098/rspb.202...
Sperm whale codas exhibit contextual and combinatorial structure: https://www.nature.com/articles/s41467-024-47221-8
Ants have developed symbolic language: https://pmc.ncbi.nlm.nih.gov/articles/PMC10093743/
Everywhere we look close enough, we find life doing smart things.
Some great apes can learn to use symbols for communication. Bees can use specific dances to indicate direction and distance.
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.
This of course changes the question as to why only/mainly homo erectus developed the capability.
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.
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.
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.
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.
Is GPU already the metaphor du jour? I thought we were still aboard the steam engine ;)
What would "intelligence" look like WHILE it was evolving?
A slightly more unsettling thought: How would newly-emerging intelligence FEEL like, internally?
Also, how would humans fare if born and raised in the wild, without any language or tools taught to them?
OOA (with minor admixture) is the consensus position for a lot of excellent reasons.
There is an assumption that belief in, or even reasonable agnosticism towards, any other theory can only be motivated by racism.
There are many people that believe OOA because they want to believe it, because they want to believe we are all more similar than we are different, etc.
Multiregional hypotheses are perfectly plausible. We have very limited information one way or another. Out of Africa may be more likely but it is far from certain.
This is completely and unequivocally rejected by the genetic evidence. The evidence is so absolutely overwhelming that even fucking Wolpoff came around and now says:
Now, if you mean something completely different to the commonly understood definition of multiregionalism, I'm willing to hear it.But, also, There are many people that [do not] believe OOA because they [do not] want to believe it.
That's why we look at genetic evidence, to eliminate nonsense. That evidence strongly points to chimps, gorillas, humans etc all coming from the same place.
If it makes you feels better, think of it this way:
we don't believe OOA because the evidence says we're related to blacks. We believe it because the evidence says we're pretty much hairless apes. (And a lot of us aren't even hairless!)
There, feel better about it now?