I think I expressed this unclearly. Lifespan is more tightly correlated to brain size than body size (brain size scales disproportionately with body size). The author gives the example that if lifespan was correlated with our body size, humans would live 20-25 years, but since lifespan is correlated to our brain size, our expected lifespan is longer.
I agree that the correlation doesn’t necessarily point to a causal linkage.
I think I expressed this unclearly. Lifespan is more tightly correlated to brain size than body size (brain size scales disproportionately with body size). The author gives the example that if lifespan was correlated with our body size, humans would live 20-25 years, but since lifespan is correlated to our brain size, our expected lifespan is longer.
I agree that the correlation doesn’t necessarily point to a causal linkage.
Guess: animals that live longer get more value from learning over their lifespans and so they benefit more from (expensive) large brains.