Thicker cerebrospinal fluid: Results?

How can I achieve this[?]

Make them cavemen.

Cerebrospinal fluid (CSF) keeps the brain in neutral buoyancy, effectively lessening its weight against itself. This means that the brain can be heavier than it would be otherwise, meaning that it can be denser. Increasing the amount of CSF would mean that the brain could be even denser and still be neutrally buoyant. You might then see more folds in the brain, with increased surface area. Although the size of the brain will decrease, an increase in density could lead to more brain cells.

More brain cells don't necessarily correspond to greater intelligence. Homo neanderthalensis is a case in point here, with heavier brains but not necessarily greater intelligence than modern-day humans. However, a more massive brain could certainly help.

While more CSF means a smaller brain size, as bowlturner said, it might still lead to an increase in brain mass.

How could you get a thicker layer of CSF? I'm always inclined to say that randomness in evolution will lead to a variety of different results; the mutation in question simply has to significantly affect the organism enough to make it dominant in a species (or lead to a new species). This means that environmental factors may come into play, and I'm inclined to say that the possibility for a slightly higher average intelligence won't be as important.

Therefore, I would suggest that the reason for a thicker layer of CSF could be motivated by its ability to protect the brain. Perhaps the humanoids live in an area where they get banged up quite a bit. They might live in caves that have an unfortunate tendency to cave in, or in forests that tend to have a lot of falling trees. The point is, I'm pretty sure that they'll need to have an environment where they get hit on the head a lot.

Now, a thicker layer of CSF won't necessarily mean a denser layer of CSF, and given that (as Samuel pointed out) the density of the fluid is what determines buoyancy, it might not lead to a substantial effect. So I enter Crazy Scenario #1, which is that the humanoids manage to - on a small scale - change the size/shape of their skulls for some purpose. Perhaps they need to squeeze into small places (tiny cave tunnels) to hide, hibernate, or live, which means they have to somehow change the shape of their bodies. This would mean that an alternate skull structure/material is needed. Cartilage could be used here. It is still hard, but not as hard as bone, meaning that some deformation is allowed (although not a lot - think of what it's like to have a broken nose!).

Unlikely? Perhaps. But cave-dwelling humanoids living in small tunnels (if you'll run with my one of my suggested premises) are bound to be different.

Ville Niemi suggested higher gravity an another factor that might be important. Impacts would be even more forceful, leading to a need for substantially stronger cushioning.

posted about 9 years ago

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