If our ancestors' mental abilities increased in parallel with an increase in brain size,why has the size of our brains not continued increasing?

Question

Quizplus · Accepted Answer

Brain size is only one factor in determining cognitive abilities. Other factors such as genetics and environment also play a significant role. Additionally, there may be diminishing returns in terms of cognitive ability as brain size increases beyond a certain point. Therefore, simply increasing brain size may not necessarily result in a significant increase in cognitive ability.

If Our Ancestors' Mental Abilities Increased in Parallel with an Increase