Animals become indifferent to their young as soon as their young can look after themselves, but human beings, owing to the length of infancy, find this less easy.

• 译文：动物对自己的后代的态度是：一旦它们能够自立，就不再关注它们；但是由于人的婴儿时期太长，父母很难停止关注自己的孩子。