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Science

Scientists Discover How Humans Develop Larger Brains Than Other Apes (phys.org) 77

fahrbot-bot shares a report from Phys.org: A new study is the first to identify how human brains grow much larger, with three times as many neurons, compared with chimpanzee and gorilla brains. The study, led by researchers at the Medical Research Council (MRC) Laboratory of Molecular Biology in Cambridge, UK, identified a key molecular switch that can make ape brain organoids grow more like human organoids, and vice versa. The study, published in the journal Cell, compared "brain organoids" -- 3-D tissues grown from stem cells which model early brain development -- that were grown from human, gorilla and chimpanzee stem cells.

During the early stages of brain development, neurons are made by stem cells called neural progenitors. These progenitor cells initially have a cylindrical shape that makes it easy for them to split into identical daughter cells with the same shape. The more times the neural progenitor cells multiply at this stage, the more neurons there will be later. As the cells mature and slow their multiplication, they elongate, forming a shape like a stretched ice-cream cone. Previously, research in mice had shown that their neural progenitor cells mature into a conical shape and slow their multiplication within hours. They found that in gorillas and chimpanzees this transition takes a long time, occurring over approximately five days.

Human progenitors were even more delayed in this transition, taking around seven days. The human progenitor cells maintained their cylinder-like shape for longer than other apes and during this time they split more frequently, producing more cells. This difference in the speed of transition from neural progenitors to neurons means that the human cells have more time to multiply. This could be largely responsible for the approximately three-fold greater number of neurons in human brains compared with gorilla or chimpanzee brains.

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Scientists Discover How Humans Develop Larger Brains Than Other Apes

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  • Only some of them. (Score:2, Informative)

    by Chas ( 5144 )

    There's a great number of monkeys out there in society operating on mostly brain stem, topped with solid bone.

  • by Venik ( 915777 ) on Wednesday March 24, 2021 @09:27PM (#61195066)
    A sperm whale's brain weighs 18 pounds, and an African elephant's brain has three times the number of neurons of a human brain. Every day I work with apes who have giant heads, and, frankly, I am not impressed.
    • by Immerman ( 2627577 ) on Wednesday March 24, 2021 @10:20PM (#61195238)

      When it comes to neurons more pretty much is better - but better doesn't map directly to intelligence. Neurons get used for a lot more than abstract reasoning.

      Take the elephant for example - while a human that has an oversized "thinking" portion of our brain, an elephant has an oversized "muscle control" portion of their brain. Which makes sense - a human has about 600 muscles in our body, while an elephant's trunk alone has 40,000. It seems that combination of power, flexibility, and fine muscle control comes with a hefty neural operating cost.

      • by dinfinity ( 2300094 ) on Thursday March 25, 2021 @06:33AM (#61195980)

        True, humans have a far larger number of neurons in the cerebral cortex than almost all other animals. See https://en.wikipedia.org/wiki/... [wikipedia.org]

        Obviously, that is not the entire story of intelligence, given that a number of cetaceans handily beat us in this regard. It seems that having a lot of cortical neurons is a prerequisite for intelligence, not a guarantee.

        The topology and thus function of the neurons is a very important factor, which isn't really surprising. The same holds for artificial neural networks but also for CPU transistor count vs. topology with regard to performance.

        • by Immerman ( 2627577 ) on Thursday March 25, 2021 @09:04AM (#61196446)

          Very true.

          Of course it's also possible that whales actually do have us handily beat in intelligence - it's just a form sufficiently alien that we can't appreciate its scope. Without hands the whole "tool making" thing has severely limited potential, and a whole lot of our abstract reasoning ability could be readily understood as making tools out symbols. Whales in contrast seem to have a huge amount of their brainpower involved in their sonar, and appear to have a truly astounding ability to extract vast amount of fine detail from what would seem to be a very limited one-dimensional information stream. If that capacity forms a cornerstone of their intelligence, similar to how our visual cortex appears to be heavily involved in our own symbolic reasoning, I can't even begin to imagine the ways in which their thought processes might differ from ours.

          And of course the lack of a common language severely undermines our ability to evaluate their intelligence beyond the most primitive problem-solving abilities. Their language does appear to be considerably simpler than human languages - which would seem to count against their intelligence - but then I've also heard suggestions that they may also be able to actually project artificial sonar images to each other, which could be halfway to telepathy for communicating complex concepts, and greatly reduce the value of complex language in the first place.

          • Whales in contrast seem to have a huge amount of their brainpower involved in their sonar, and appear to have a truly astounding ability to extract vast amount of fine detail from what would seem to be a very limited one-dimensional information stream.

            I've always thought dolphin intelligence experiments that revolve around an LCD screen are butt stupid. To the dolphin, it's an unchanging flat panel to their most important sense. Trying to get them to look at it is ridiculous. Dolphin experiments should involve distinct sonar shapes, not visual shapes.

    • You are (a) ignoring the complexity of the body (dividing neurons by body mass is a good start), and (b) considering all cells equal (you should really exclude motor neurons).

      If you do this, only the long-finned pilot whale is remotely similar. Even the bottlenose dolphin has only half the significant brain to body mass ratio. Most animals aren't remotely close to even that.

      You also have to consider neuron size. Avian neurons are smaller than mammalian neurons, so an equal mass gives an unequal neuron count

  • by Ostracus ( 1354233 ) on Wednesday March 24, 2021 @09:28PM (#61195068) Journal

    OK, so what happened when you left the switch on constantly?

    • OK, so what happened when you left the switch on constantly?

      I'd expect they keep multiplying as pre-neurons and never become neurons. Instead of forming a brain the foetus dies of prenatal brain-tissue cancer.

    • That probably won't work, but Neanderthal brains were slightly larger) just not as well structured), so it should be possible to set the switch to that size with modern human brain architecture.

      • by carton ( 105671 )

        That probably won't work, but Neanderthal brains were slightly larger) just not as well structured)

        This sounds suspicious. Do we have evidence neanderthals were dumber than humans because their brains were less well-structured, or are we just assuming humans were smarter because we're the humans, then making up reasons for that?

        • by hondo77 ( 324058 )

          Do we have evidence neanderthals were dumber than humans because...

          I think the evidence is along the lines of "we are here and they are not (for the most part)".

        • by jd ( 1658 )

          No, there's not a shred of evidence that Neanderthals were dumber. There is limited evidence they invented art, symbolic representation, proto writing and maps.

          All we know for certain is that they had a different brain layout similar to that of other apes, but that it was larger than the modern human brain by a decent amount.

          Some of that went into superior eyesight and superior sense of smell, but all parts of the brain were enlarged so that's not the whole story.

          But because we know, in advance, that the ho

    • This? [amazonaws.com]

  • by 278MorkandMindy ( 922498 ) on Wednesday March 24, 2021 @09:41PM (#61195106)

    ... welcome our new Monkey Overlords.

    "What could go wrong?"

  • A few CRISPER edits and they will become our slaves.
  • How 'bout we get genetic engineer started figuring out how to prolong this prolonged process so that we can get smarter humans that can do things to make the process more prolonged, and then prolong the prolonged process so that we can get humans who have had prolonged progenitors that are the most prolonged progenitors that ever were prolonged. Quick! Before SkyNet come online! N2CH
  • So, what has been seen as food in certain countries might now be seen as future soldier material there. The physique and the natural aggressive tendencies of some great apes, combined with human level intelligence will lead to interesting war footage

  • Let me guess... It was from playing a lot of video games?

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