Sentence:  Again the <WSD>student</WSD> of evolutionary biology will find a fascinating , if to our minds grotesque , anticipation of the theory of chance variations and the natural elimination of the unfit in Lucretius , who in turn seems to have borrowed the concept from the philosopher Empedocles . 
Meaning of the word marked with <WSD> tags:  a learned person (especially in the humanities); someone who by long study has gained mastery in one or more disciplines