Mr. Redfield proceeds to argue from these facts as follows: "At one time man and ape reproduced at the same average age, whereas now they reproduce at widely different ages. Going back to the time when man and ape separated, our ancestors survived by physical and mental activity in securing food and escaping from enemies. As time went on man reproduced at later and later average age until now he reproduces at about thirty years from birth of parent to birth of offspring. When time between generations stretched out in the man line more than it did in the ape line, the man acquired MORE MENTAL DEVELOPMENT BEFORE HE REPRODUCED than did the ape, and he did this because he was mentally active more years before reproducing. The successive generations leading to modern man transmitted to offspring more than they inherited from their parents, and the generations which did this are the same generations which acquired, before reproducing, the identical thing which they transmitted in excess of inheriting. "Coming now to those rare men of whom we have only a few in a century, how were they produced? It should be noted that each one had two parents, four grandparents, and eight great-grandparents. Also that they are certainly improvements over their great-grandparents. If they were not such improvements, then there would be many 'rare' cases in a century. In looking into the pedigrees of these great men it is found that they were sons of parents of nearly all ages, but were predominantly sons of elderly parents. While we sometimes find comparatively young parents in the pedigree of a great man, we never find a succession of young parents. Neither do we find an intellectually great man produced by a pedigree extending over three generations. The great man is produced only when the average for three generations is on the elderly side of what is normal. The average age of one thousand fathers, grandfathers, and great-grandfathers in the pedigrees of eminent men was found to be over forty years. Great men rise from ordinary stock only when several generations in succession acquire mental efforts in excess amounts before reproducing."