alt Hacker News> my theory is that selection will remove memes (behavioral/thought/cultural patterns) that cause childlessness from the meme pool much faster.
The sociologist Eric Kaufmann wrote a book Shall the Religious Inherit the Earth?, arguing that traditionalist religious groups (such as ultra-Orthodox Jews and the Amish) will become demographically dominant in the long-term (decades and centuries) due to their greater fertility and high retention rates (>80% of their children stay in the group as adults)
I think the possiblities that a minority can leave the group is an important escape valve for them. Now assume that in the future they are going to be not such a minority anymore like today, then what happens? Maybe some oscillation like for Lotka-Volterra situation, perhaps a bit different?