Darwinism is a system of thought regarding how organisms change over time. Based on the writings of Charles Darwin, modern neo-Darwinism usually embraces an entirely materialist view of the universe…that is, that physical matter is all that exists, and that there is not spiritual or metaphysical aspect of reality.
A common claim among those who believe that Darwinian evolution adequately explains life as we know it is that humans have a lot of leftover parts from our primitive ancestors. Whether it's 'junk DNA' or vestigial organs, the idea is that our ancestors needed these parts for survival, but that we no longer need them.