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From the NPR link [0]: > The researchers analyzed the brain sizes and diets of over 140 primate species spanning apes, monkeys, lemurs and lorises and found th

From the NPR link [0]: > The researchers analyzed the brain sizes and diets of over 140 primate species spanning apes, monkeys, lemurs and lorises and found that those who munched on fruit instead of leaves had 25 percent more brain tissue, even when controlling for body size and species relatedness. [0] https://www.npr.org/sections/thesalt/2017/03/27/521423216/what-gave-some-primates-bigger-brains-a-fruit-filled-diet https://www.npr.org/sections/thesalt/2017/03/27/521423216/wh...

culi 4y ago
Kinda funny to think about because leaf-eaters tend to have larger more complex gut microbiomes. Your gut microbiome has been called "the second brain" because the majority of neurotransmitters (including over 90% of all seratonin) originates there. It almost seems like there's a tradeoff between the two "brains" This would explain why pandas, koalas, and sloths (all leaf-eaters) are often thought of as "dumb" lol
- yababa_y 4y ago
  The neurotransmitters in the gut do _not_ make it across the blood-brain barrier, and there certainly isn’t a direct tradeoff between behavioural complexity and the stew of monoamines in your gut.
  - tffcccdredf 4y ago
  - dataangel 4y ago
    Prucalopride and other gut motility meds that contain neurotransmitters often have depression/suicide warnings, so some sort of information transmission is happening, even if it's not that the transmitters directly cross the barrier.
- bpodgursky 4y ago
  Can't really explain elephants in that case.
  - culi 4y ago
    Elephants actually do eat a lot of fruit as well. But yeah it was definitely a playful hypothesis and not a serious proposal. I'm sure if I researched it for even 10 minutes I could find a lot of examples that disprove it
- nobody9999 4y ago
  >Kinda funny to think about because leaf-eaters tend to have larger more complex gut microbiomes. Your gut microbiome has been called "the second brain" because the majority of neurotransmitters (including over 90% of all seratonin) originates there. Leaf eaters also tend to have larger jaw muscles and attachments for same. That tends to limit the size of the brain case, as that space is needed for the chewing apparatus and supporting skeletal features[0]. [0] https://www.nature.com/articles/news040322-9 https://www.nature.com/articles/news040322-9
  - culi 4y ago
    Fascinating, thanks! I remember seeing a lecture by an anthropologist who showed a graph that mapped the size of different primates vs what percent of their day they spend just chewing food. Chimps spend about 60% of their days just chewing for example. The trendline was a surprisingly effective predictor for other primates. Except for humans. Based on our mass we would expect humans to spend around 70% of our day just chewing. Instead it's less than 10% Another point of evidence that supports the hypothesis put forth in the OP
cbdc_watcher 4y ago
That's funny. If I had a bigger brain I too would munch on fruit instead of leafs. I think they have it backward causation wise.
- awestroke 4y ago
  If you had a bigger brain, you would automatically have access to fruit? That seems backward causation wise

culi 4y ago

Kinda funny to think about because leaf-eaters tend to have larger more complex gut microbiomes. Your gut microbiome has been called "the second brain" because the majority of neurotransmitters (including over 90% of all seratonin) originates there. It almost seems like there's a tradeoff between the two "brains" This would explain why pandas, koalas, and sloths (all leaf-eaters) are often thought of as "dumb" lol

yababa_y 4y ago
The neurotransmitters in the gut do _not_ make it across the blood-brain barrier, and there certainly isn’t a direct tradeoff between behavioural complexity and the stew of monoamines in your gut.
- tffcccdredf 4y ago
- dataangel 4y ago
  Prucalopride and other gut motility meds that contain neurotransmitters often have depression/suicide warnings, so some sort of information transmission is happening, even if it's not that the transmitters directly cross the barrier.
bpodgursky 4y ago
Can't really explain elephants in that case.
- culi 4y ago
  Elephants actually do eat a lot of fruit as well. But yeah it was definitely a playful hypothesis and not a serious proposal. I'm sure if I researched it for even 10 minutes I could find a lot of examples that disprove it
nobody9999 4y ago
>Kinda funny to think about because leaf-eaters tend to have larger more complex gut microbiomes. Your gut microbiome has been called "the second brain" because the majority of neurotransmitters (including over 90% of all seratonin) originates there. Leaf eaters also tend to have larger jaw muscles and attachments for same. That tends to limit the size of the brain case, as that space is needed for the chewing apparatus and supporting skeletal features[0]. [0] https://www.nature.com/articles/news040322-9 https://www.nature.com/articles/news040322-9
- culi 4y ago
  Fascinating, thanks! I remember seeing a lecture by an anthropologist who showed a graph that mapped the size of different primates vs what percent of their day they spend just chewing food. Chimps spend about 60% of their days just chewing for example. The trendline was a surprisingly effective predictor for other primates. Except for humans. Based on our mass we would expect humans to spend around 70% of our day just chewing. Instead it's less than 10% Another point of evidence that supports the hypothesis put forth in the OP

cbdc_watcher 4y ago

That's funny. If I had a bigger brain I too would munch on fruit instead of leafs. I think they have it backward causation wise.

awestroke 4y ago
If you had a bigger brain, you would automatically have access to fruit? That seems backward causation wise