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> There IS a correlation between intelligence and brain size (of about 0.3). Here is a page that shows what such a weak correlation looks like visually: https

by czl 2y ago

> There IS a correlation between intelligence and brain size (of about 0.3). Here is a page that shows what such a weak correlation looks like visually: https://resources.nu.edu/statsresources/correlation https://resources.nu.edu/statsresources/correlation It also explains that a correlation of r = 0.3 means only about 9% of the variability in one variable is explained by the other. This makes me wonder: can intelligence really be estimated within 10% accuracy? I doubt it, especially considering how IQ test results can vary even for the same person over time. Kids and teens have smaller brains, but their intelligence increases as they experience more mental stimulation. It’s not brain size that limits them but how their brains develop with use, much like how muscles grow with exercise. > a chimp brain is not likely to produce (adult, healthy) human-level intelligence. > Human brains consume significantly more calories than chimp brains. If brain size and calorie consumption directly drove intelligence, we’d expect whales, with brains five times larger than humans, to be vastly more intelligent. Yet, they aren’t. Whales’ large brains are likely tied to their large bodies, which evolved to cover great distances in water. Brains can large like arms can be large but big arms do not necessarily make you strong -- they may be large due to fat. > But generally, over the last several million years, human intelligence has been rising sharply. Yes, smaller-brained animals are generally less intelligent, but exceptions like whales and crows suggest that intelligence evolves alongside an animal’s ecological niche. Predators often need more intelligence to outsmart their prey, and this arms race likely shaped human intelligence. As humans began living in larger communities, competing and cooperating with each other, intelligence became more important for survival and reproduction. But this has limits. High intelligence can lead to emotional challenges like overthinking, isolation, or an awareness of life’s difficulties. Highly intelligent individuals can also be unpredictable and harder to control, which may not always align with societal or biological goals. As I see it, ecological niche drives intelligence, and factors like brain size follow from that. The relationship is dynamic, with feedback loops as the environment changes.

trashtester 2y ago
> As I see it, ecological niche drives intelligence For this, you're perfectly correct. > It’s not brain size that limits them but how their brains develop with use, much like how muscles grow with exercise. Here, the anser is yes, but like for muscles, biology will create constraints. If you're male, you may be able to bench 200kg, but probably not 500kg unless your biology allows it. > If brain size and calorie consumption directly drove intelligence, we’d expect whales As you wrote later, there are costs to developing large brains. The benefits would not justify the costs, over evolutionary history. > Brains can large like arms can be large but big arms do not necessarily make you strong -- they may be large due to fat. A chimp has large arms. Try wrestling it. > and factors like brain size follow from that Large brains come with a significant metabolic cost. They would only have evolved if they provided a benefit that would outweigh those costs. And in today's world, most mammal tissue is either part of a Homo Sapiens or part of the body of an animal used as livestock by Home Sapens. That's evolutionary "success" for you.
- czl 2y ago
  > biology will create constraints. If you're male, you may be able to bench 200kg, but probably not 500kg unless your biology allows it. On evolutionary timeframes what biology allows can evolve and the hard limits are due to chemistry and physics. > there are costs to developing large brains. The benefits would not justify the costs, over evolutionary history. > Large brains come with a significant metabolic cost. They would only have evolved if they provided a benefit that would outweigh those costs Google "evolutionary spandrels" and you will learn there can be body features (large brains of whales) that are simply a byproduct of other evolutionary pressures rather than direct adaptation.
  - trashtester 2y ago
    > Google "evolutionary spandrels" and you will learn there can be body features (large brains of whales) that are simply a byproduct of other evolutionary pressures rather than direct adaptation. If you're a 10-150 ton whale, a 2-10 kg brain isn't a significant cost. But if you're a 50kg primate, a brain of more than 1kg IS. For humanoids over the past 10 million years, there are very active evolutionary pressures to minimize brain size. Still, the brain grew to maybe 2-4 times the size over this period. This growth came at a huge cost, and the benefits must have justified those costs. > On evolutionary timeframes what biology allows can evolve and the hard limits are due to chemistry and physics. It's not about there being hard limits. Brain size or muscle size or density is about tradeoffs. Most large apes are 2-4 times stronger than humans, even when accounting for size, but human physiology has other advantages that make up for that. For instance, our lower density muscles allow us to float/swim in water with relative ease. Also, lighter bodies (relative to size) make us (in our natural form) extremaly capable long distance runners. Some humans can chase a horse on foot until it dies from exhaustion. I'm sure a lot of other species could have developed human level intelligence if the evolutionary pressures had been there for them. It just happens to be that it was humans that first entered an ecological niche where evolving this level of intelligence was worth the costs.
    - czl 2y ago
      > Also, lighter bodies (relative to size) make us (in our natural form) extremaly capable long distance runners. Humans' ability to run long distances effectively is due to a combination of factors, with the ability to sweat being one of the most crucial. Here are the key adaptations that make humans good endurance runners: a) Efficient sweating: Humans have a high density of sweat glands, allowing for effective thermoregulation during prolonged exercise. b) Bipedalism: Our two-legged gait is energy-efficient for long-distance movement. c) Lack of fur: This helps with heat dissipation. d) Breathing independence from gait: Unlike quadrupeds, our breathing isn't tied to our running stride, allowing for better oxygen intake. Lighter bodies (relative to size) plays a role but there plenty of creatures that have light bodies relative to size that are not great at long distance running.

by czl 2y ago

trashtester 2y ago

> As I see it, ecological niche drives intelligence For this, you're perfectly correct. > It’s not brain size that limits them but how their brains develop with use, much like how muscles grow with exercise. Here, the anser is yes, but like for muscles, biology will create constraints. If you're male, you may be able to bench 200kg, but probably not 500kg unless your biology allows it. > If brain size and calorie consumption directly drove intelligence, we’d expect whales As you wrote later, there are costs to developing large brains. The benefits would not justify the costs, over evolutionary history. > Brains can large like arms can be large but big arms do not necessarily make you strong -- they may be large due to fat. A chimp has large arms. Try wrestling it. > and factors like brain size follow from that Large brains come with a significant metabolic cost. They would only have evolved if they provided a benefit that would outweigh those costs. And in today's world, most mammal tissue is either part of a Homo Sapiens or part of the body of an animal used as livestock by Home Sapens. That's evolutionary "success" for you.

czl 2y ago
> biology will create constraints. If you're male, you may be able to bench 200kg, but probably not 500kg unless your biology allows it. On evolutionary timeframes what biology allows can evolve and the hard limits are due to chemistry and physics. > there are costs to developing large brains. The benefits would not justify the costs, over evolutionary history. > Large brains come with a significant metabolic cost. They would only have evolved if they provided a benefit that would outweigh those costs Google "evolutionary spandrels" and you will learn there can be body features (large brains of whales) that are simply a byproduct of other evolutionary pressures rather than direct adaptation.
- trashtester 2y ago
  > Google "evolutionary spandrels" and you will learn there can be body features (large brains of whales) that are simply a byproduct of other evolutionary pressures rather than direct adaptation. If you're a 10-150 ton whale, a 2-10 kg brain isn't a significant cost. But if you're a 50kg primate, a brain of more than 1kg IS. For humanoids over the past 10 million years, there are very active evolutionary pressures to minimize brain size. Still, the brain grew to maybe 2-4 times the size over this period. This growth came at a huge cost, and the benefits must have justified those costs. > On evolutionary timeframes what biology allows can evolve and the hard limits are due to chemistry and physics. It's not about there being hard limits. Brain size or muscle size or density is about tradeoffs. Most large apes are 2-4 times stronger than humans, even when accounting for size, but human physiology has other advantages that make up for that. For instance, our lower density muscles allow us to float/swim in water with relative ease. Also, lighter bodies (relative to size) make us (in our natural form) extremaly capable long distance runners. Some humans can chase a horse on foot until it dies from exhaustion. I'm sure a lot of other species could have developed human level intelligence if the evolutionary pressures had been there for them. It just happens to be that it was humans that first entered an ecological niche where evolving this level of intelligence was worth the costs.
  - czl 2y ago
    > Also, lighter bodies (relative to size) make us (in our natural form) extremaly capable long distance runners. Humans' ability to run long distances effectively is due to a combination of factors, with the ability to sweat being one of the most crucial. Here are the key adaptations that make humans good endurance runners: a) Efficient sweating: Humans have a high density of sweat glands, allowing for effective thermoregulation during prolonged exercise. b) Bipedalism: Our two-legged gait is energy-efficient for long-distance movement. c) Lack of fur: This helps with heat dissipation. d) Breathing independence from gait: Unlike quadrupeds, our breathing isn't tied to our running stride, allowing for better oxygen intake. Lighter bodies (relative to size) plays a role but there plenty of creatures that have light bodies relative to size that are not great at long distance running.