62:4.5

Although in emotional nature the Primates differed little from their forebears, they exhibited more of a human trend in all of their propensities. They were, indeed, splendid and superior animals, reaching maturity at about ten years of age and having a natural life span of about forty years. That is, they might have lived that long had they died natural deaths, but in those early days very few animals ever died a natural death; the struggle for existence was altogether too intense.