That's not how evolution works, and it's not at all clear that a desire or lack of desire to have children is genetic or hereditary.
Yes, people who don't have kids are ending their genetic line when they die. But that doesn't mean that people who have kids are necessarily increasing the pool of people who want kids, percentage-wise.
> But that doesn't mean that people who have kids are necessarily increasing the pool of people who want kids, percentage-wise.
Yeah I imagine that large families tend to result in adults who are themselves likely to have more kids than average, but things can certainly shift. Among my extended family, for example: my grandmother was one of 11 kids, my mom was one of 7, my aunts and uncles largely had 3-4, and my cousins mostly have 2-3. This is a tight-knit crowd, with a strongly pro-family culture (Catholicism), living in proximity with regular get-togethers, neighboring lake cottages etc, but clearly not immune to broader trends.
Yes, people who don't have kids are ending their genetic line when they die. But that doesn't mean that people who have kids are necessarily increasing the pool of people who want kids, percentage-wise.