Don't worry about humanity's numbers. The "rapid-breeding" subcultures (e.g. archtraditionalist sects, pro-natalist populations) will replace those who are less

Don't worry about humanity's numbers. The "rapid-breeding" subcultures (e.g. archtraditionalist sects, pro-natalist populations) will replace those who are less willing to breed, in the long run. The problem is, of course, whether the replacement memeplex that will occur would focus on the colonisation of Solar System by Earthlife. I have no idea.