4.1122 Darwinian theory has no more to do with philosophy than has any other hypothesis of natural science.
Because evolution is only a theory? No, because philosophy is not about why we think as we do in an historical or causal sense. Nor is it about how we think in any biological sense. In this sense it isn’t about thinking at all. It is about thoughts only in the logical sense.
Schopenhauer offers an alternative to Darwinian theory in The World as Will and Representation. Presumably Wittgenstein did not subscribe to this alternative, but he might have thought that philosophy should not decide between competing scientific hypotheses. Science should do that.