Are you sure that a brain using 10 times as much energy could easily be supplied with enough calories?
Brains already use disproportionately more energy than most other parts of the body, averaging about 10 times the per-kilogram rate of the rest of the body on average. Scaling this up by another factor of 10 seems wildly optimistic. For example, the energy appetite of the brain is already so great that its function starts to be impaired within 5 seconds of ceasing supply of oxygenated blood, and about 10 seconds to unconsciousness.
Blood leaving the brain has a normal range of oxygen saturation down to around 55%, and that can’t really go very much lower without running into serious problems with existing biology. To get 10x the energy you would therefore need to increase blood flow to the brain to be ten times that of baseline humans. This is actually twice the average blood flow baseline humans typically employ for their whole body. I don’t think you could manage that without massive re-engineering not just within the brain but elsewhere as well.
This is even without considering waste products, heat dissipation, and so on that will all have their own challenges.
Thanks for a good comment. My oversimplified thought process was that a 10x increase in energy usage for the brain would equate to a ~2x increase in total energy usage. Since we’re able to maintain that kind of energy use during exercise, and elite athletes can maintain that for many hours/day, it seems reasonable that the heart and other organs could maintain this kind of output.
However, the issue you bring up, of actually getting that much blood to the brain, evacuating waste products, doing the necessary metabolism there, and dealing with so much heat localized in the small area of the brain, are all valid. While it seems like the rest of the body wouldn’t be constrained by this level of energy use, a 10x power output in the brain probably might be a problem.
It’s worth a more detailed analysis of exactly where the max. power output constraint on the brain, without any major changes, lie.
Are you sure that a brain using 10 times as much energy could easily be supplied with enough calories?
Brains already use disproportionately more energy than most other parts of the body, averaging about 10 times the per-kilogram rate of the rest of the body on average. Scaling this up by another factor of 10 seems wildly optimistic. For example, the energy appetite of the brain is already so great that its function starts to be impaired within 5 seconds of ceasing supply of oxygenated blood, and about 10 seconds to unconsciousness.
Blood leaving the brain has a normal range of oxygen saturation down to around 55%, and that can’t really go very much lower without running into serious problems with existing biology. To get 10x the energy you would therefore need to increase blood flow to the brain to be ten times that of baseline humans. This is actually twice the average blood flow baseline humans typically employ for their whole body. I don’t think you could manage that without massive re-engineering not just within the brain but elsewhere as well.
This is even without considering waste products, heat dissipation, and so on that will all have their own challenges.
Thanks for a good comment. My oversimplified thought process was that a 10x increase in energy usage for the brain would equate to a ~2x increase in total energy usage. Since we’re able to maintain that kind of energy use during exercise, and elite athletes can maintain that for many hours/day, it seems reasonable that the heart and other organs could maintain this kind of output.
However, the issue you bring up, of actually getting that much blood to the brain, evacuating waste products, doing the necessary metabolism there, and dealing with so much heat localized in the small area of the brain, are all valid. While it seems like the rest of the body wouldn’t be constrained by this level of energy use, a 10x power output in the brain probably might be a problem.
It’s worth a more detailed analysis of exactly where the max. power output constraint on the brain, without any major changes, lie.