and not even that, I'd narrow it further to not detrimental before and during the prime reproductive periods of a species. After that period, detrimental traits are totally fair game and more dependent on technology, culture, and family care dynamics. Heart disease later in life caused by genetic predisposition to high cholesterol isn't something people generally select for or against in a partner, but its effects happen later in life well after people have children so it passes on.

> Heart disease later in life caused by genetic predisposition to high cholesterol isn't something people generally select for or against in a partner, but its effects happen later in life well after people have children so it passes on.

That depends. It can still affect genetic fitness if it affects an individual's ability to confer benefits on their descendants. Of note: most of the most wealthy and influential people in our society are beyond their reproductive years (not technically true for men, but mostly true in practice).

Parents must also be alive for long enough to care for their children until they can sustain themselves.