Evolution occurs through natural selection, where organisms with genetic variations that increase their chance of survival are more likely to reproduce and pass on those genes. Over many generations, these advantageous genes become more common in a population as less adapted genes die out, resulting in changes to the species over time. Evidence from fossils, genetics, and anatomy show that humans evolved from apelike ancestors in Africa over approximately 6 million years, with early humans first emerging between 6-2 million years ago. Paleoanthropologists study human evolution by examining fossils and archaeological remains to learn about physical and behavioral traits of early humans and their ancestors.