来自《耶鲁大学开放课程：心理学导论 第12集》

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  between an animal and its children,
  它们的子女之间的关系
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  particularly in cases like humans and birds and mammals
  重点讲了人类 鸟类 哺乳类动物
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  where there tends to be a close relationship with our children.
  与他们子女的关系尤为亲近
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  We invest in quality, not quantity.
  我们注重子女质量 而非数量
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  I might produce very few children in my life.
  我可能一辈子生不了几个孩子
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  And my evolutionary trick then is to focus very intently on them
  而进化的作用使得我对他们非常关注
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  and make sure they survive.
  确保他们都能存活
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  If I were to produce 100 children,
  如果我生了一百个孩子
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  I could stand to lose a few,
  那失去几个我也能受得了
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  but if I just produce five in my lifetime or two or one,
  但如果我一辈子就生了五个或两个或一个
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  they become very precious to me.
  对我而言他们就十分珍贵了
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  And so, the story of the evolution of a species like us
  因此 在像人类这样的物种进化过程中