collective flexibility

A young mind is like a dough. It is extremely flexible but also useless. As it ages, it becomes more useful but less flexible.

However this trade-off occurs only at the individual level. The collective mind does not lose any flexibility at all, because it solves different types of problems by mobilising different types of individuals.

As people age, they lose mental flexibility but gain physical and social mobility which in turn allows the collective mind to work its magic.

Remember. We are all servants of the collective mind. What looks like an arbitrary trade-off at an individual level is often the local manifestation of an optimal solution to a global problem.