Real men arose, we believe, by variational uplifts of considerable magnitude which led to big and complex brains and to the power of reasoned discourse. In some other lines of mammalian evolution there were from time to time great advances in the size and complexity of the brain, as is clear, for instance, in the case of horses and elephants. The same is true of birds as compared with reptiles, and everyone recognises the high level of excellence that has been attained by their vocal powers. How these great cerebral advances came about we do not know, but it has been one of the main trends of animal evolution to improve the nervous system. Two suggestions may be made. First, the prolongation of the period of ante-natal life, in intimate physiological partnership with the mother, may have made it practicable to start the higher mammal with a much better brain than in the lower orders, like Insectivores and Rodents, and still more Marsupials, where the period before birth (gestation) is short. Second, we know that the individual development of the brain is profoundly influenced by the internal secretions of certain ductless glands notably the thyroid. When this organ is not functioning properly the child's brain development is arrested. It may be that increased production of certain hormones--itself, of course, to be accounted for--may have stimulated brain development in man's remote ancestors. Given variability along the line of better brains and given a process of discriminate sifting which would consistently offer rewards to alertness and foresight, to kin-sympathy and parental care, there seems no great difficulty in imagining how Man would evolve. We must not think of an Aristotle or a Newton except as fine results which justify all the groaning and travailing; we must think of average men, of primitive peoples to-day, and of our forbears long ago. We must remember how much of man's advance is dependent on the external registration of the social heritage, not on the slowly changing natural inheritance. Looking backwards it is impossible, we think, to fail to recognise progress. There is a ring of truth in the fine description AEschylus gave of primitive men that-- first, beholding they beheld in vain, and, hearing, heard not, but, like shapes in dreams, mixed all things wildly down the tedious time, nor knew to build a house against the sun with wicketed sides, nor any woodwork knew, but lived like silly ants, beneath the ground, in hollow caves unsunned. There came to them no steadfast sign of winter, nor of spring flower-perfumed, nor of summer full of fruit, but blindly and lawlessly they did all things.