As all the children were still too young to go into the details of either menstruation or venerea diseases, it was considered best to dwell on the early tribes of man on up to marriage, and wait for future developments before going further. The tree dwellers and cave dwellers were already familiar stories to them. The fact that people lived together very closely; that the woman had great freedom in choosing the man whom she wished to be the father of her child, even as freely as the animals chose their mates; that in this freedom great mistakes were often made, such as that for a period some mothers chose their sons or brothers, or fathers to be the father of the new little one; that after a time it was found that this was very injurious to this new little child, for he often could not walk, or talk, and was weak, and sometimes a cripple—and more often died very young. So the chiefs of these tribes got together and said this must not be, for if this continued there would be no strong young men or women to till the soil or fight off the animals, wild beasts or the enemy. Then a law was made that only those of the different tribes or families should choose each other for the parents of the future children, and here the lesson of the Buttercups came in—that often Mrs. Buttercup would reject the pollen from the stamen in her own house, but would accept the pollen from another buttercup house and become fertilized with that. The part the two sexes took in different ways to strengthen and develop the race seemed of great interest to the children. The work of hunting and fishing was left to the men of the family, while equally important work, that of cleaning and cooking the food, was for the women. Men spent much time in making tools and weapons. They were able to save much time and energy when the bow and arrow was invented, for, instead of taking all the time to creep upon a beast or enemy with a knife or sharp stone, he could remain at a distance and do the same work. Thus, men got a little more leisure time. With every new invention their labor and energy was saved, but it took much longer for labor-saving inventions for the women to come into use.