The title question occurred to me when on the show Wild Kratz they asked the question, "Why do monkeys have these particular features etc.?" Upon hearing this, I wondered if "why?" was the right thing for them to be asking. My understanding of the word Why is that deals in meaning. And science, by definition, cannot deal with meaning. It can discuss mechanisms, causes and effects, and consequences, but strictly speaking, it's only talking about what mechanically happens, not why something happens in the first place. Meaning, per se, is outside the legitimate bounds of scientific inquiry.