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New Study Has Scientists Reevaluating Relative Brain Size and Mammalian Intelligence 53

Posted by BeauHD from the let's-revisit-this dept.
An anonymous reader quotes a report from Phys.Org: Scientists from Stony Brook University and the Max Planck Institute of Animal Behavior have pieced together a timeline of how brain and body size evolved in mammals over the last 150 million years. The findings, published in Science Advances, show that brain size relative to body size -- long considered an indicator of animal intelligence -- has not followed a stable scale over evolutionary time. The international team of 22 scientists, including biologists, evolutionary statisticians, and anthropologists, compared the brain mass of 1400 living and extinct mammals. For the 107 fossils examined -- among them ancient whales and the most ancient Old World monkey skull ever found -- they used endocranial volume data from skulls instead of brain mass data. The brain measurements were then analyzed along with body size to compare the scale of brain size to body size over deep evolutionary time.

According to the study, "big-brained" humans, dolphins, and elephants, for example, attained their proportions in different ways. Elephants increased in body size, but surprisingly, even more in brain size. Dolphins, on the other hand, generally decreased their body size while increasing brain size. Great apes showed a wide variety of body sizes, with a general trend towards increases in brain and body size. In comparison, ancestral hominins, which represent the human line, showed a relative decrease in body size and increase in brain size compared to great apes. The authors say that these complex patterns urge a re-evaluation of the deeply rooted paradigm that comparing brain size to body size for any species provides a measure of the species' intelligence. The study has been published in the journal Science Advances.
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New Study Has Scientists Reevaluating Relative Brain Size and Mammalian Intelligence More

New Study Has Scientists Reevaluating Relative Brain Size and Mammalian Intelligence

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  • Common Knowledge (Score:4, Funny)

    by oldgraybeard ( 2939809 ) on Friday April 30, 2021 @09:06AM (#61331668)
    The aliens messed with our DNA for fun and profit

  • Composition seems far more important (Score:5, Insightful)

    by alvinrod ( 889928 ) on Friday April 30, 2021 @09:25AM (#61331720)
    We know enough about the human brain to map certain types of cognition on to different parts of the brain. We can identify similar structures in other present day mammals as well and not all of them have the same proportion of neurons in their brains. Crows, despite having a physically small brain have about the same number of neurons as many primates in a region analogous to the cerebral cortex, which is what's responsible for the behavior we tend to think of as intelligence. Elephants have much larger brains, both physically and in terms of total neurons, but the vast majority are responsible for motor control because an elephant's trunk has almost 100 times as many muscles in it as the entirety of the human body. Octopuses are even more fascinating because their brain seems to be a lot less centralized compared to mammals and we're trying to figure out the implications of that, but they're also quite intelligent by animals standards.

    Think of it a bit like computer components. You can have billions of transistors in a computer system, but the way they're arranged plays a big difference in what that system will be good at. If most of them were devoted to GPU cores, you have something that may be good at some particular workloads, but it's going to delivery good frame rates if you wanted it to run Crysis. Shift those transistors to an arrangement like those in a GPU and now they're far, far better and tackling that specific problem.
    • What I don't understand is why intelligence doesn't correlate with brain size alone, but rather intelligence correlations to the ratio of brain and body size.

      For example it's obvious why the size of the heart must correlate to body size - a much larger number of cells need nutrients.

      The large number of muscles in an elephant trunk needing a lot of neurons for control is interesting but doesn't quite seem to touch on what is meant by "intelligence."

      So for example the richness of animal communication -

      • That's the point. Elephants brains are bigger because (simply put) they have more to physically control in their bodies. But they aren't building rockets now are they. Maybe if they were doing calculus, their brains would be even bigger.

        I've also seen some writing about the type of brain matter being important. That is, white matter and grey matter. For example, proportionally dolphins have a significantly greater amount of white matter in their brains than humans, and less grey matter. White matter tran

        • Re:Composition seems far more important (Score:5, Informative)

          by MightyMartian ( 840721 ) on Friday April 30, 2021 @11:10AM (#61332088) Journal

          There are significant biological costs to larger brains. They require a great deal more energy to operate, so right off the bat you require more food, so the pay off has to be at least some greater ability to forage or hunt for food. Probably, at least in hominoids, the single greatest cost to a large brain is fetal development and birth. Relatively speaking, the great apes (including humans) are born quite premature as compared to other animals. It's a simple engineering problem; the larger the brain, the more the female reproductive system has to be altered to allow fetal development and birth. But there are constraints. If gestation goes on too long, then the pelvic region will have to be that much wider, and the wider the pelvic region the more difficult it would be for females to move about, making them more vulnerable to predation and injury.

          So, in the great apes, and in particular in humans, evolution has had to make a large compromise. The shape and size of the pelvis is wider to allow a longer gestation period, but not so wide that it severely impacts movement. That's why women have a different center of gravity to men, why their hips are wider, and why in general men can run more swiftly (since the male pelvis does not have to accommodate a wider birth canal). But ape infants are in fact still born quite prematurely as compared to many other mammals, leaving infants both underdeveloped relative to other mammals (in effect, gestation continues outside the womb), and in a position of much longer post-natal care. It is what has shaped the social systems of all the apes, and has had enormous ramifications on how ape society is structured and functions. The bigger ape brain comes with a helluva lot more processing power, more problem solving capability, more ability to produce complex and effective societies, so the pay off is worth the much greater risks in longer fetal gestation, greater risks to mother and fetus, and the much longer development before the offspring are able to fend for themselves.

          • Good point. Economics is key. It has to pay for itself. People forget that aspect about nature. It's why top predators rarely actually fight and instead bluster and intimidate if they can. Doesn't pay to get hurt in a turf war. I guess I implicitly think of it now, why I made the reference to catching fish.

      • Re: (Score:2)

        by dvice ( 6309704 )

        > What I don't understand is why intelligence doesn't correlate with brain size alone,

        "We found that we have, on average, 86 billion neurons,"

        "So, a rodent brain with 86 billion neurons would weigh 36 kilos."

        "And what we found is that because neurons are so expensive, there is a tradeoff between body size and number of neurons. So a primate that eats eight hours per day can afford at most 53 billion neurons, but then its body cannot be any bigger than 25 kilos. To weigh any more than that, it has to give

    • Crows, despite having a physically small brain have about the same number of neurons as many primates in a region analogous to the cerebral cortex, which is what's responsible for the behavior we tend to think of as intelligence.

      Birds (modern dinosaurs!) do a trick in brain organization that makes them fast and small though still powerful.

      Unlike mammals, birds don't put most of the processing for muscular coordination in the brain. They put it further down the spine. (That's why a "chicken with its head

      • ... the processing nerves can be closer together - more of a lump than a sheet spread over the front of a bigger lump. So the signals don't have as far to go.

        That also reduces the amount of neural material used for just getting the signal around, further reducing the volume for a given amount of processing.

    • Re: (Score:2)

      by Z80a ( 971949 )

      You ain't getting a lot of performance out of a huge die made of thousands of S3 Virge chips.

    • This is similar to what I was going to post. A good example would be hound dogs compared to poodles. They might both have similar brain/body ratios, but a much larger percentage of the hound dog's brain is dedicated to olfactory processing. So the poodle is "smarter" (easier to teach tricks to) while the hound dog is a better scent tracker.

      It's easily forgotten the brain primarily deals with things other than cognition. Some animals are capable of some amazing physical feats—and they use a lot of brai

  • It's called heterochrony (Score:5, Informative)

    by The Real Dr John ( 716876 ) on Friday April 30, 2021 @09:33AM (#61331742) Homepage

    Stephen Jay Gould published a classic work on it many years ago: "Ontogeny and Phylogeny". I highly recommend it if you are interested.

    • That one's a real slog to get through. He has some essays which explain the basic points of that work without having to read the book itself. Ontogeny and Phylogeny is interesting if you want to do a deep dive into the subject and explore the history of how science arrived at that point. However, it's sort of a historical read in itself. We know so much more about genetics today and it is interesting comparing Gould's speculations with modern observations. What's even more interesting is when an article lik

  • that comparing brain size to body size for any species provides a measure of the species' intelligence.

    This was an old first cut idea anyway, after raw brain size embarrassed humans. For some time they've known number of connections between each neuron (as a neural network) and number of convolutions in the surface (presumably the bulk of thinking is in a relatively thin sheet on the outside) have more relevance.

  • Mammalian brain size (Score:4, Interesting)

    by Freischutz ( 4776131 ) on Friday April 30, 2021 @09:46AM (#61331784)

    New Study Has Scientists Reevaluating Relative Brain Size and Mammalian Intelligence

    Yeah, when palaeontologists start talking about 'large-brained hominids' they sound like a bunch of drunk frat boys suffering from a severe case of toxic testosterone poisoning who are comparing the cup sizes of their favourite Hooters waitresses. But all fun aside, If the Dmanisi finds [wikipedia.org] finally proved anything, since there were multiple specimens of adult Homo Erectus who lived contemporaneously but that had wildly differing brain sizes, it is that there is no direct connection between brain size and intelligence. If that was the case the sperm whales with their 10 kg brain would be veritable living super computers and rulers of this planet. Same for modern humans. Groups of humans with a relatively small body size and therefore small brain size have created great civilisations and they did it way before groups with a relatively larger average brain size did. It is the wiring of the brain that matters a whole lot more than size. You can use a super computer for nothing more than playing Pong, while somebody else uses a laptop to do serious scientific work. In this case it's what software you run on the computer and what you do with it that matters as much as raw size and CPU power.

    • If the Dmanisi finds [wikipedia.org] finally proved anything, since there were multiple specimens of adult Homo Erectus who lived contemporaneously but that had wildly differing brain sizes, it is that there is no direct connection between brain size and intelligence.

      It only proves that you act like a drunken frat boy when you see the taxonomic name Homo erectus. They used tools. They interbred with other humans. There is no objective reason to believe they were less intelligent than other humans who are given a different taxonomic status.

  • Most science proponents loosely use the term religion. Some because all the religions they know are opposed to evolution. Some because they want to avoid blaming specific groups. Others are simply careless or indifferent.

    But opposition to evolution comes from a few specific denominations of Abrahamic religions. By avoiding the broad brush science should be able to find a lot more friends among the faithful. Hinduism and Buddhism do not quarrel with science on this issue at all. Nor do most non-fundamentali

    • Most science proponents loosely use the term religion. Some because all the religions they know are opposed to evolution. Some because they want to avoid blaming specific groups. Others are simply careless or indifferent.

      But opposition to evolution comes from a few specific denominations of Abrahamic religions. By avoiding the broad brush science should be able to find a lot more friends among the faithful. Hinduism and Buddhism do not quarrel with science on this issue at all. Nor do most non-fundamentalist Christians.

      No, scientists and 'science proponents' dismiss religions because, after thousands of years of asking for proof of the existence of gods, all you get from the religionists to this day is either a ton of nonsense that contributes nothing to the quest of proving the existence of their god or you just get: **cricket**, **cricket**, ... Admittedly there are a few religionists that just say that you have to take the existence of god on blind faith which at least constitutes some semblance of honestly admitting t

      • Re:Not all religions are opposed to evolution. (Score:5, Interesting)

        by 140Mandak262Jamuna ( 970587 ) on Friday April 30, 2021 @02:11PM (#61332860) Journal
        This is precisely the view of people who have encountered only proselytizing and evangelizing religions.

        There are religions that will never ever ask you to change your beliefs or worship their God. They don't merely tolerate your disbelief on their deities, they genuinely accept and agree that that disbelief does not make you a bad person, nor does it make you a sinner nor is your eternal soul is condemned for ever. You might not believe you have an eternal soul, but they do, and they say "its ok, he does not worship Vishnu, that is fine, there must be a reason why Vishnu made him that way. Who am I to question Vishnu? The Lord must have planned a different route for his salvation". There are such religions, only you were not aware of them. Because of the antagonistic and confrontational attitudes of the proselytizers and evangelists you are reacting harshly to mild, non threatening religions.

        There is a very simple secular scientific reason why religious beliefs arose. We people are affected by random events we have no control over. Two thousand years ago, when people did not even know about rain cycle or germ theory of disease the perceived randomness would be even higher. A band of brothers might take herds out for grazing, when they return three days later, the entire village might have been washed away in a flood, or be overrun by another tribe, or a devastating disease might have decimated the population. The chances were extremely high for personal experience of such tragedies, not something recalled and narrated by Memory Fathers over camp fires. Unless you develop methods to stay optimistic, things will be fine, there is Someone I Trust, who is all powerful, who will protect my family because I have done all the things expected by Him, you would have died of despair. People who could develop such optimism died out. Those who believed in God survived. Repeat enough times, it explains the rise of religions.

        You have no reason to be so antagonistic against religions that have never imposed their will or beliefs on you. Give them the same benefit you accord to people who believe tax cuts would lead to job growth or universal basic income would lead to a productive society. Agree with them or disagree, vote with them or against them.

        If it is possible for you to show respect to religions that do not evangelize that will help. You will not be used as a symbol of God hating heathen who must be opposed, so please show up in my place of worship and donate money to me. Deny them fund raising opportunities, please. If you can.

      • Can you explain what causes gravity ?

        (Actual rational explanation, not primary school stuff - 2 bodies attract each other)

        You are free to google or talk to the best scientists.

        If you fail, think about why you kept believing the primary school stuff when it's clearly wrong ?

        It's not at all necessary for things to be "proved" for them to be useful for us, so we do certain things based on generations of experience which is passed on in various mundane ways, including the parent/teacher/boss's "because I said

        • Sorry, slashdot seems to keep posting my reply in the wrong f*'ing place.

          It was in reply to:
          Freischutz
          "No, scientists and 'science proponents' dismiss religions because, after thousands of years of asking for proof of the existence of gods, all you get from the religionists to this day is either a ton of nonsense that contributes nothing to the quest of proving the existence of their god or you just get: **cricket**, **cricket**, ...."

        • Can you explain what causes gravity ?

          Gravity doesn't need to have a "cause" because there are, apparently, no gravitron particles that distribute the force.
          It appears that what we call "mass" is a localized deformation of space-time. Gravity is merely our expectation that this surface would be flat; however, it is not. Gravity is the human brain not being able to form an intuitive understanding of space-time. That will not have a clear, simple "cause" that you can point at, like a monkey pointing at the full moon as the source of the night's l

          • Re: (Score:2)

            by ami.one ( 897193 )

            What I can make out is that you agree that believing in something like God or Religion is no different from believing in the explanations for gravity that we have been taught.

            So you need certain amount of starting belief before you can hope to study / understand anything further whether its science or arts or religion...
            Then after 20 years of studying that field maybe, just maybe, you are qualified to say what's right or wrong.

            So in this case, people (incl me) with no religious interest or aptitude (beyond

            • What I can make out is that you agree that believing in something like God or Religion is no different from believing in the explanations for gravity that we have been taught.

              Sortof; believing in anything is a means, a tool. But the arrogance of human ignorance is broad, and powerful. We tend to think that what we believe is somehow Really True, For Real. But the physical substance of our thoughts is just an electro-chemical organ, not a magical thing-knower. The closest we can come is to internalize language that describes a thing, and this internalization is no more the thing than the description in a book is. And we have no scale on which to place it and be told that we had i

      • Can you explain what causes gravity ?

        (Actual rational explanation, not primary school stuff - 2 bodies attract each other)

        You are free to google or talk to the best scientists.

        If you fail, think about why you kept believing the primary school stuff when it's clearly wrong ?

        It's not at all necessary for things to be "proved" for them to be useful for us, so we do certain things based on generations of experience which is passed on in various mundane ways, including the parent/teacher/boss's "because I said s

  • How long until job interviews require a recent brain scan?

    • How long until "people" get that the point of a brain is to make most work unneccessary.

      Like walking around the hole so you do not have to climb and cure your wounds and eat more.
      Like making a machine that makes you your wealth, instead of slaving away to create wealth. Especially if most of it does not even go to you.

      The wealthy have understood that. It's just that they use us as robots (Polish for "workers").

      • Things in this world do not come for free. Even if you run your own business you have customers, we all work for someone.

  • We've got African Grey parrots - one timne, one congo.

    They have phone conversations, where one rings the phone, the other says a variant of 'hello' (different for different people they're imitating), then they mumble (differently each time), some uh huhs, some OKs, some 'yeah's, then one of several variants of goodbye then beep.

    They also hold up food, and tell the dogs (by name) to 'sit' - then praise them 'good boy' or 'good girl' after tossing the food - they especially do it when the dogs are annoying th

    • The neuron density should definitely be checked.

      Let's use the total number of neurons and of connections between them as basic values for comparison.
      (And special features, like better insulation, higher sensitivity to electric fields, broadcasting abilities, or different synapse chemistry, to get more precise values.)

      Go look up how long your fully unfolded DNA is, of which there are multiple copies in each cell. I forgot, but it's somehing longer than your entire body, I think.
      Neurons may also have the abil

    • Intelligence is a funny thing. I remember reading a paper many years ago that suggested one of the differences between humans and chimps appeared to be that we could hold more information in short term memory at the same time than chimps. It would be analogous to the difference between an 8 bit and a 16 bit computer. Sure, an 8 bit computer can do 16 bit integer arithmetic, but it usually requires more cycles, and in some cases moving registers to the stack (in effect, moving short term memory to long term

  • This is comparing brain size to body size.

    Brain size does not relate much to intelligence, as crows demonstrate. Nor does body size, obviously. So brain/body size relationship has no basis to link it to intelligence.

    • Except that the brain/body size ratio actually *does* correlate reasonably well with intelligence, when comparing average intelligence of similar species.

      Very often such ratios are far more fundamental than any individual measure. For example the strength-to-weight ratio of animal's muscles holds far more steady across species than either strength or weight alone - essentially the ratio is looking at cellular properties rather than macroscopic body properties.

      It's also been pretty well established for deca

  • Smaller adult humans have a larger brain-to-size ratio ergo tall people aren't smarter than shorter ones so quit deifying tall people.

  • In my opinion, suggesting that natural selection is how evolution works is like suggesting that wheels are how a car works. Our understanding of the process of evolution is utterly incomplete, and will stay that way given the dogmatic nature of the field.

  • According to the study, "big-brained" humans, dolphins, and elephants, for example, attained their proportions in different ways. Elephants increased in body size, but surprisingly, even more in brain size. Dolphins, on the other hand, generally decreased their body size while increasing brain size. Great apes showed a wide variety of body sizes, with a general trend towards increases in brain and body size.

    Ok, but now how do you explain my political opponents? Their body size trends upwards while their intelligence rapidly approaches microscopic. Science can't explain that!

  • Whole of the animal kingdom has just turned on Consciousness. IQ was bragging rights for the few specie that were smart. No longer are we the lone few nor alone.

    IQ has been disrupted

  • Consensus for a while has been that it's the brain's surface area that's important, not volume. Did people really still think you can tell relative intelligence based on size? Neanderthal had bigger brains than us. Did people think this meant they were smarter?

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