The theory, however, which is most generally favored at the present time holds that, assuming the universality of the evolutionary process, all existing types must be of equal antiquity, and none prior or ancestral to any other. Hence it regards man, not as the direct descendant of any known type of ape, but as the offspring of an as yet undiscovered Tertiary ancestor, from which men and apes have diverged in two distinct lines of descent. “_Monkeys, apes, and men_,” says Conklin, “_have descended from some common but at present extinct ancestor_. Existing apes and monkeys are collateral relatives of man but not his ancestors; his cousins but not his parents.... The human branch diverged from the anthropoid stock not less than two million years ago, and since that time man has been evolving in the direction represented by existing human races, while the apes have been evolving in the direction represented by existing anthropoids. During all this time men and apes have been growing more and more unlike and conversely the farther back we go, the more we should find them converging until they meet in a common stock which should be intermediate between these two stocks.” (“Evolution and the Bible,” pp. 12, 13—italics his.) Barnum Brown’s recent discovery of three jaws of the fossil ape _Dryopithecus_ in the Siwalik Hills of India has, as previously intimated, resulted in a return on the part of certain scientists, _e.g._ Wm. K. Gregory and Dudley J. Morton, to views that more nearly approximate those of Charles Darwin. According to these men, the fossil anthropoid _Dryopithecus_ is to be regarded as the common ancestor of men, chimpanzees, and gorillas. (Cf. _Science_, April 25, 1924, Suppl. XII.) Many considerations, however, militate against the direct derivation of man’s bodily frame from any known species of ape, whether living or fossil. Dana has pointed out that, as regards the mechanism of locomotion, man belongs to a more primitive type than the ape. The earliest and lowest type of vertebrates are the fish, and these, according to the above-mentioned author, are _urosthenic_ (tail-strong), inasmuch as they propel themselves by means of their tails. Next in point of organization and time came the _merosthenic_ vertebrates, which have their strength concentrated in the hind-limbs, _e.g._ reptiles like the dinosaurs. In the last place come the _prosthenic_ vertebrates, whose strength is concentrated in the fore-limbs, _e.g._ the carnivora and apes. Now man belongs to the _merosthenic_ type, and his mode of progression, therefore, is more primitive than that of apes, which are _prosthenic_, all anthropoid apes, such as the gorilla, the chimpanzee, the orang-utan and the gibbon having longer fore-limbs than hind-limbs.