Initiative in Evolution

by Walter Kidd

How the Hair is Arranged on the Forearm.

Returning now to the text, the remarkable arrangement of hair on man’s forearm, attention may be directed to the accompanying figure of the forearm of a lemur, an ape and man, in which the extensor or back view of this limb-segment is shown, the heavy “war-arrows” being employed to direct the attention of the reader to the main lines in which the hair-streams flow. The front or flexor surfaces in the lemur and ape are not shown because they are precisely like the corresponding back surfaces, and the flexor surface in man is shown in the figure. The figures are so much like diagrams that a very little detailed descrip­tion will suffice. For the examina­tion of the hair on man’s forearm the best subject is a dark-haired youth, and it is easily traced, though in any hairy subject it can be shown up well by placing the forearm in water for a minute and allowing the water to drain off. The normal and congenital hair-slope on the forearm is then well displayed.

On the front surface of man’s forearm the hairs point away from the elbow and divide in the middle of the surface into two streams, one passing to the outer and the other to the inner border in a downward gentle curve, and they join the streams of hair on the back surface. In this pattern there is nothing very peculiar, for it is shared by many monkeys.

When the back surface is examined it is found to present an arrangement of the hair which is unique among hairy mammals. The figure shows the eccentric course taken by the hair on the back surface. In the centre, exactly along the extensor border of the ulna, from the wrist to the point of the elbow, the hair-stream has been bold enough to turn straight upwards in a narrow line, and it was here that our three great leaders saw their chance of claiming for Selection a tiny bit of territory, a kind of Duchy of Luxembourg between two great States, though, as I proceed to show, the claim is disallowed and untenable.

Fig 1.—Arrangement of Hair on the Forearm.

In the ape the hairs of the forearm are much longer and thicker than those of man, and both on the front and back all point from the wrist to the elbow.

In the lemur all the hairs point from the elbow to the wrist.

In the products of Nature there are no freaks, or impish tricks performed, and it is not for nothing she does her work. Every one of them asks for and should receive an explana­tion consistent with fact and reason, and here comes in the need for studying, as one may, the broad outlines of man’s ancestry. His ancestor being now sought in an earlier and more generalized stock than that of the four genera of anthropoid apes known to us, the most instructive and safest line to take is to trace him back to the stock lemur, who remains to-day among the most Chinese or unchanging of known mammals. In his illuminating work, Prehistoric Man and History, Professor Scott Elliott adopts an excellent term, “lemur-monkey-man,” to sum up, without missing links, the long ancestry of man. I take the liberty of adapting this term more closely to the present inquiry and use that of lemur-ape-man instead, for whatever may be the relation of man to present apes some ape-like ancestors enter into his genealogical tree.[45] For my purpose the monkey is less useful because his hair-slope differs so little from that of lemurs, whereas apes have made for themselves a very remarkable position as regards the hair of their forearms. Our series of animals for study is then well represented by the lemur-ape-man—hypothetical, necessary and serviceable. Through all the immense stretch of time occupied in this process of descent there has been ample opportunity for the lemur to change his fashion to that of the ape, and the latter to change to the present fashion of man.

This simple arrangement of the lemur’s hair is common to that of all the more primitive long-bodied mammals, of which an otter is a good example, and I venture, greatly daring, to call this the normal slope of hair. Somewhere and somehow in the human tree there has appeared a total reversal of the lemur-type; the stock of apes acquired a new fashion, and gradually discarded altogether their ancient inheritance, beginning their innova­tion perhaps, with Dryopithecus fontani in the Miocene Age.