How does evolution explain complex organisms like humans?

How does evolution explain complex organisms like humans?

Answer: 

Evolution doesn’t happen all at once, especially in complex organisms such as human beings. Modern humans are the product of evolutionary processes that go back more than 3.5 billion years, to the beginnings of life on Earth. We became human gradually, evolving new physical traits and behaviors on top of those inherited from earlier primates, mammals, vertebrates, and the very oldest living organisms.