Natural selection always favors fecundity over all else.

I have two colleagues (biologists) whose conversation I'll related as best I can. The one I label "F" is amazingly productive, literally hundreds of pubs to his name, devised several new analytical methods, etc. The one I label "J" is a middle-of-the-road scientist -- dependable but not creative or innovative.

"J": My oldest son had a great soccer weekend. Won a couple of games.
"F": My wife and I went bicycling and I worked on a paper and she sold a house.
J: I mowed the lawn and my wife had the night shift at the hospital.
F: If you arranged your life better you would be more productive. Kids often prevent scientists from reaching their full potential.
J: I have 4 kids by two wives and one grandchild. It keeps me busy.
F: I believe my success has been due to my not having children and staying focused on my job.
J: How do you define success?
F: Publications, citations, grad students.
J: And you claim to be a biologist?

(I could've blown coffee through my nose onto the windshield)