According to Darwin's law of survival of the fittest will atheists die out

because they don't reproduce. In order for any species, group or culture to live on they need to reproduce. Atheists might be able to survive as a group by passing on this belief system to those who are not their children but usually Christian families create Christian children and atheists much the same. There are always exceptions but I'm wondering if the lack of child-bearing will hurt their cause. In eastern Europe where Atheist communists killed off any religious belief they are losing population dramatically. Russia has a net loss of 800,000 a year. American and Western Eurpean atheists are much the same being way under the replacement level. Is this cultural suicide. The religious usually have way more children and teach them their traditions. Any thoughts?