One answer is kin selection.

第一个答案是亲缘选择。

Reciprocal altruism and kin selection are the two main theories.

互利主义和亲族选择是两个主要理论。

One is known technically as kin selection, and familiarly as nepotism.

一种就是所谓的血缘选择，即家庭亲戚关系。

Though not conclusive, these results fall in line with the kin selection hypothesis.

尽管并非决定性结论，但这些结果验证了同族选择假设理论。

One possible explanation is what evolutionary psychologists call the "kin selection hypothesis."

心理学家提出了一种可能的解释，称之为“亲族选择”假说。