20017
Theoretical models predict that ( 1 ) it is adaptive for an individual to be altruistic to any other individuals that are more closely related to it than this average level , and also that ( 2 ) it is adaptive for an individual to be spiteful against any other individuals that are less closely related to it than this average level .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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