We humans are more similar to each other as a group than we are to one another within any particular racial or genetic category. Many anthropological books have been written to explain this phenomenon (for recent examples see Tattersall and DeSalle 2011; Smedley and Smedley 2012; Relethford 2013; Jurmain et al. 2014; and Mukhopadhyay, Henze, and Moses 2014).
