To win the future, you need to have kids

And leftists don't.  When taken with scientists' rather robust finding that children's politics correlate highly with those of their birth parents (with an r square of 0.6 - very high) this means that societies demographically trend patriarchal and conservative.

It turns out that leftism is a self refuting philosophy.

LEFTIST ENCLAVES ALWAYS SEEM TO TURN OUT THIS WAY: San Francisco Becoming Child-Free Zone As Youth Population Declines.