What would be the evolutionary conditions that would lead us to mentally think we are older as we age? For much of evolutionary history we were expected to produce offspring then kick the bucket. No advantage to feeling older, not even expected to get that much older than what most people feel.

If we solved the problem of aging this wouldn’t be a puzzle at all and it would immediately make perfect sense. The age we feel we are would correspond roughly to the age we were fully developed (mid 20s) and the age our body would stay at without aging.