Logical flaw in darwinism

How elementary could the flaws in Darwin's logic be? How's this?

Only one or two of each living creature's progeny get to reproduce and pass on their genes (natural selection). Every few hundred million years there's a huge meteor impact. Therefore, natural selection causes meteor impacts.

Compare that with the following:

Only one or two of each living creature's progeny get to reproduce and pass on their genes (natural selection). Over millions of years species of living creatures tend to evolve. Therefore, natural selection causes evolution.

I think the logic in both is the same. Both are examples of post hoc ergo propter hoc, the fallacy of assuming that because one thing happens before another it must have caused the other. More...