An agile body can foreshadow, or more accurately, try out possible genetic adaptations, and then hold a steady line to them, as a hunting dog holds to a grouse.

• 灵活的身体能够预示，或者更精确地说，能够选拔出基因可能适应的东西，然后一直保持对它们的兴趣，就像猎狗一直喜欢松鸡一样。