Theory in human evolution is concerned with explaining the facts and observations of human biology, behaviour and existence. Most theories of human evolution are Darwinian, in the sense that they explain observations about humans in the past and the present in terms of the action of natural selection, i.e. how novel human traits are adaptive and provide a reproductive advantage, and so become widespread and fixed.

Theories of human evolution can be focused on specific traits, and providing an explanation for these – why are humans ‘hairless’ compared to apes? Why do humans grow more slowly than apes?

Alternatively they can focus on the larger patterns of change – Why is Africa central to human evolution? Does climate drive human evolutionary change?

Within scientific studies of human evolution there is general acceptance that a good theory of human evolution will be a Darwinian one, but there are many debates about the best specific theories (or alternative Darwinian hypotheses) that explain particular observations.

Beyond science, there are non-Darwinian theories of human evolution (humans were planted on earth by aliens), as well as religious based creation myths. In the end, a theory of human evolution is an attempt to explain why humans exist, and how they have come to be like they are. Theories of human evolution compete with religious explanations in not invoking the supernatural or special agency, but focus on laws applicable to all living forms, and in being testable.