Hamilton's rule.
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   The kin selection advantage can be quantified by measuring 3 values.
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   The benefit to the recipient (B)
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   The cost to the altruist (C)
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   The coefficient of relatedness (r):
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<BR><LI> Sibling 1 has inherited the allele from parent A.
<BR><LI> There  is  a  probability  of 1/2 that sibling 2 will also inherit
this allele from parent A.
<BR><LI> The r between the two siblings is 1/2 (0.5).
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   Kin selection favors altruism when rB > C.
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