It's quite remarkable the sacrifices that were made for the sake of increasing cranium size. Childbirth became a coin-flip for whether the child and mother even survive the ordeal, infants are born completely helpless for the first few months of life. It goes to show just how critical intelligence was for the survival of our species.

Dominant traits is not always about survival... Could be a sexual preference for intelligence. Nerds might have been cools a few 100 k years before we thought!

If you were smarter you could better tools, weapons and shelter... Or better ways to hunt and prepare food...

That would definitely help your family survive better.

Your parent makes the valid point that difficulty in producing such children does not necessarily demonstrate the value of this trait for survival. Peacock tail confers no survival merit except for sexual selection.

It very strongly demonstrates the value of the trait for gene survival, which is the important thing. The individual matters not.