What caused humans to become the top species on earth, and why is there such an intellectual gap between humans and all other species?
In: Earth Science
As strange as it sounds, meat played a large part. Flesh is much more calorically dense than plant matter, so when our ancestors transitioned from an entirely/mostly plant based diet to one then included a fair amount of meat, it meant our bodies had more energy to devote to the brain. In modern humans, the brain is *incredibly* expensive, taking up ~20% of our caloric intake. So having extra energy to burn meant we could evolve better brains.
Short answer is that evolution is a crazy, random process caused by random mutations. If that mutation is beneficial, it gets passed down (as that individual is more likely to survive and thrive). Apparently, having a larger brain was more beneficial for our ancestors. This could be because having more tool-making skill increased survival, it helped us socialize and work together, etc.
At some point, we became a dominant species. This would increase selection pressure for intelligence, because now we’re competing with ourselves instead of against the rest of the natural world. If intelligence is what helps me reproduce more often, it makes sense that we would increase in intelligence.
Other animals don’t need larger brains because they haven’t proven to help increase survival rates. There’s actually a lot of downsides to a large brain. One of these is that it takes up a lot of energy: if I’m low on food, having a large brain is actively harmful because it’s burning energy without helping me. Big brains also equal big skulls, making birth much more difficult. For a lot of animals, being born with a fully formed brain is important so that they can start feeding themselves immediately. Humans give birth to offspring with undeveloped brains. This is beneficial in that it allows us to have a larger and more complex brain when we reach maturity, but the downside is that we can’t fend for ourselves right out of the womb.
Intelligence is expensive.
Having a well developed brain costs a lot of energy, and – for generational improvement – requires a lot of parental nurturing. That means you can only develop it in settings where there is ample energy, and a very useful trait is having sufficiently cohesive social structures to support the parenting, teaching, and development of the young, as well as having enough free time to develop skills and technology which apply that intelligence.
That requires a number of other traits to develop beforehand or alongside. For us there were several imporotant developments, which included (but certainly wwere not limited to):
1. Fine motor skills and physical strength to enable tool use
2. Access to higher energy foods. This was done through the control of fire, and the development of agriculture (or at least communal hunter-gathering, allowing some individuals to not need to be out exposed to the environment to feed themselves). Both are dependent on number 1.
3. Having a sufficiently cohesive social order that you can dedicate some individuals to specific tasks, while freeing up others to experiment with supporting young, developing new skills, passing those skills on to others, and so on. That is facilitated by the development of complex language (and hence feeds back into benefits of greater intelligence, and so on)
4. The physiology to allow development of larger brain cavities – birthing something with a massive head is a physiological challenge, and the fragility and skeletal requirements are not insignificant. Young gazelle and impala (and their mothers) can run within minutes of being born. They are much better addapted to surviving around lions than we are.
The costs in developing intelligence are very high, but once you have an edge the impact snowballs – it becomes a positive feedback loop where the intelligence allows further refining and honing of the environment to allow further developments.
You can’t look on intelligence as a single element that is beneficial on its own; it’s not. You have to have other complimentary physical, social and environmental conditions that allow it to flourish. In a sufficiently aggressive or hostile environment intelligence becomes a burden, because immediate survival of the young to the point where they can reproduce becomes the primary driver, and the nurturing required for the other elements that fed into the development of intelligence across a species get missed out.
I’m sure there’s some evolutionary biologists around who can refine this with better info, but this is the broad picture (at least as I understand it).
Nobody knows for sure because we weren’t around back then to study it.
It appears that higher intelligence is *sometimes* extremely beneficial, but usually it isn’t.
If some mad scientist made a tiger 10 times as intelligent as it currently is, well the tiger probably wouldn’t get that much out of it. It’s already a great hunter, it doesn’t really need to be smarter. It might be able to sit down and scratch out math equations in the dirt with its paws, but that doesn’t help it be a better killer — not by enough to make a difference. What it would do is dramatically increase the calories that the tiger had to eat every day. Brains use up a bunch of calories anyway, and the smarter you are, the more it uses. Our poor super-tiger might starve to death if it didn’t have enough food available.
So it seems that you need the right environmental conditions. A species has to at least survive okay with its existing level of intelligence. Then you get some random mutations where some of the offspring are a little smarter. And in the right environment, that intelligence makes a survival difference. The smarter ones survive at a higher level than the baseline creature does. It might be the idea of picking up a rock, or maybe it’s primitive communication, but we aren’t sure what that first discovery was.
So the smarter descendants do a lot better than their dumber parents. Maybe the dumber creatures were barely scraping by, but the ones who could grasp the idea of picking up a rock suddenly thrived. “Oh, this is waaay easier…” they discover. The thing is, you probably need several consecutive versions of that to get to humanity.
The biggest intellectual leaps are probably “make stick sharp”, “me can talk some”, and “fire make food taste good”. Each of those is a giant leap forward in survival ability. But increases in intelligence that *don’t quite* get you to those break points… man that’s just extra calories you need for not much benefit.
We’re not the top species, that’s the same illusion that makes religious people think god created humans specially to be different to other animals. Bacteria are doing great too and I bet they’ll outlast humans by a loooooong stretch. Evolution doesn’t do “top species”.
We have language, and I think that lets us do group intelligence… and allowed us to invent writing, which allows us to have ideas that take international groups of people many human lifetimes to develop.
A lot of the technology that helps us *appear to* dominate the planet is only possible because we work together in huge groups, building on ideas developed over 100s of years.
We’re impressive… to ourselves… but I think we’d be way less impressive if we suddenly forgot to speak languages, read and write.
Not a full answer but early branches of intelligent humanoids re-converged to a single species. Such as early humans and Neanderthals. This is a natural phenomenon that occurs when a species has a desire to mate with a diverse genetic profile to create a more resilient offspring. If this process creates a less than desirable offspring natural selection will cause a shrinking population of those with undesirable traits.
The oldest writings in the world are Mesopotamian cuneiform texts. One of those texts is the Eridu Genesis. It says gods landed on earth and terraformed it to mine gold. Part of the terraforming was creating plants and animals. The gods decided mining was too much work, so they created Neanderthals and other ape men, to use as slaves. One of the gods got tired of managing the ape men, so he had his sister genetically modify some of them into modern humans with the ability to retain and pass on knowledge. This gift of knowledge to humans has been repeated in later stories of different religions like the serpent and the apple, Prometheus and the gift of fire, the blood of Kvasir, etc. This is the oldest explanation from over 5000 years ago.
Language and writing. We developed a flexible way to efficiently convey new knowledge between ourselves, and beyond a single generation.
For a small percentage of us who are skilled at extracting and improving that knowledge, it compounds like interest, and those people pull our society forward in a positive feedback loop that leaves nearly every generation slightly smarter than the last.
As others have mentioned, intelligence consumes a lot of energy, so what really allows us to be smart is what we eat, and what do humans eat differently? COOKED FOOD, you get way more resources out of food if we cook it, so we could actually fuel our brains without hurting other body parts.
We also have a lot of skills that allow us to show that intelligence to their maximum potential, having thumbs and being bipedal allow us to wield tools and carry more stuff, being social allows us to specialize in things other than “FIND FOOD!” and also:
BABIES ARE REALLY DUMB, we learn a lot but for our brains to get that advanced it takes a lot of time, other animals are born and are ready to walk in minutes babies require constant protection for years, they know nothing but they can learn way more, they have way more brain plasticity, so if you’ve ever wondered why babies are so useless that’s why
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