Few modern writers have written more sagely on old age than N. S. Shaler, late professor of geology at Harvard.[101] He attaches great importance to the interval between the end of the reproductive period and death, which in lower creatures is very brief if it exists at all. In domesticated animals there is hardly any normal old age and they do not seem to know a climacteric. There is a great variation among different races in this period of senescence, which is so peculiar to man. This interval is very brief among savages. But with the beginning of speech all the relations of the individual to his group change. If old animals live on, they do so to themselves and not for the benefit of their kind. But in man the old individual becomes a storehouse of acquired or traditional knowledge, and wisdom has, for the first time, a distinct value in organic association. It was in this way that the reproductive period was shortened, or perhaps we had better say that life was prolonged beyond it. In civilized society the old are still members of the species, not aliens or enemies. When a people begins to have a literature or a religion and a large body of mores as social inheritance develops, the value of old age increases. The old have to maintain a more dignified demeanor. They are readapted and can go on with life as before, especially as they now have eyes and teeth preserved. The best attitude toward the old is one that assures a broader view of life and better sense of values and marks the modern passage from the earlier division of men into ranks and occupations, in which women, youth, and old men were once separated from the active and militant class. Thus the position of the aged is now bettered by keeping in close relation with their fellows.