The earth is filled with life forms of enormous complexity .
Many modern scientists are materialists.
That is, they believe physical matter is the only ultimate reality. They suppose that everything in the cosmos, including life, can be explained in terms of interacting matter. Materialists do not accept the existence of spiritual or supernatural forces. Most scientists are not strict materialists. The materialists say that life, since it's made up of atoms, molecules, and chemical reactions, is just simply chemistry and nothing else and that life originated by chance chemical reactions.