Charles Darwin agreed with the unifying theory of life sciences.
 Darwin himself insisted that social policy should not simply be guided by concepts of struggle and selection in nature
 With The Descent of Man, and Selection in Relation to Sex published in 1871, Darwin set out evidence from numerous sources that humans are animals, showing continuity of physical and mental attributes, and presented sexual selection to explain impractical animal features such as the peacock's plumage as well as human evolution of culture, differences between sexes, and physical and cultural racial classification, while emphasising that humans are all one species

