Man's most human characteristic is not his ability to learn, which he shares with many other species, but his ability to teach and store what others have developed and taught him.
Female animals defending their young are notoriously ferocious and lack the playful delight in combat which characterizes the mock combats of males of the same species. There seems very little ground for claiming that the mother of young children is more peaceful, more responsible, and more thoughtful for the welfare of the human race than is her husband or brother.
It is utterly false and cruelly arbitrary... to put all the play and learning into childhood, all the work into middle age, and all the regrets into old age.