Sentence:  When race is restricted to the biological viewpoint, two opposite positions are encountered: (1) race detractors, who believe race is a pure social concept and has no biological reality and (2) <WSD>race realists</WSD> (Malik, 2012), who believe race has some biological reality, is not only a mere vision of the mind, and could be a usual proxy for biomedical studies. 
Meaning of the word marked with <WSD> tags:  One who believes that the human species is divided into observable races. (from 20th c.)