These curves—which of course give only a graphic representation of quantitative relations whose general character we all know—indicate that heredity, including under the term both stability and variability of the stock, is more potent than social tradition or physical environment. We have these races forming by their own inherent genius a social environment far beyond anything the world had ever witnessed, but when this was at its maximum it had not power to counteract the weakening influence of race admixture and exhaustion of the stock. The physical environment also remained the same, and those who would account for Greek and Roman culture by the favorable position of the two Mediterranean peninsulas—their climate, soil, coast line
and the like—should tell us why these could not maintain what they had formed. Why should the Greeks then have resisted the countless hordes of Persia, while recently on the same ground they fled before a few thousand Turks? Physical environment and social tradition may be conditions of development, but they are not its efficient causes.
Following the extraordinary development of the two nations of classical antiquity we have a decline, not sudden, for Rome still produced soldiers and writers, the Christian Church had its leaders and theologians, and the Greeks witnessed their Indian summer in Alexandria. But the light fails toward the fifth century—never, however, to be quenched, for there were always one or two to pass on the torch until the fire was rekindled in newer races. In Britain, in Germany and in France there developed centers of civilization. The mixed races of Italy gave birth to an art and a literature rivaling that of Greece. The Roman Catholic Church fairly established its authority by the great men it produced. It was a strange time, all Europe was in turmoil, but universities were established and the arts of peace flourished in the midst of wars.
The curve shows a rise from the tenth century increasing in rapidity as it proceeds. As the list includes only men no longer living, and as many of those born during the first half of the nineteenth century were still living and had not even attained eminence when the books of reference on which the list is based were compiled, the absolute numbers of those born since 1800 have no value, but they serve for comparison
