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Among the goals of ethnology have been the reconstruction of human history , and the formulation of cultural invariants , such as the incest taboo and culture change , and the formulation of generalizations about " human nature " , a concept which has been criticized since the 19th century by various philosophers ( Hegel , Marx , structuralism , etc . ) .
 Hegel, Marx
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Hegel, Marx