NATURE’S WORKSHOP.

Hokitika Guardian, 7 June 1923, Page 3

NATURE’S WORKSHOP.

MYSTERIES OF GROWTH. THE TAIL IN MAX. LONDON, April lb Yesterday Sir Arthur Keith continued at the Royal Institution lii.s course of lectures on the Machinery of Human Evolution. He discussed the methods employed hv Nature ill getting rid of structures which have become useless in the human hotly. Nature, he said, was almost absurdly conservative in the way in which she kept on reproducing certain structures which had long since ceased to serve their original purpose. She was like a saving housewife who kept storing away odd pieces of material with the idea that some (lay they would he useful. There still remains in every one of us, it seems, a vestige of the "palatial” nose with its nerve leading off to the brain. 11l animals which have this structure fully formed it is placed near the floor of the nose, just above a passage in the roof ol the mouth. In browsing animals, like the sheep, it serves a most use!ul purpose by sampling the odours of food as soon ns it passes the portals of the lips and front teeth. In man this structure is ail heirloom dating from a pre-ape stage of evolution, lor as soon as hands were developed and iuod could he lifted and sampled by smelling there was no use for it.

The Now Zealand Sphenodon or Tualara, one of the oldest ol reptiles, slill has a pineal eye with lens complete although the power of sight is not there. This the creature has inherited from some far-off ancestor. Possibly a fish found excellent use tor an eye on the top of the head. Rut the possession has been continuously handed on until it now takes the form In man of the small pineal body without lens and without nerves embedded deep in the brain. It lias persisted because it has been converted to serve

a new purpose. Jn recent times it has been found that it has an important part to play m the regulation of growth. WHY MAN LOST lilS HAIR. Every member of the great order of animals to which man belongs is clad in a hairy covering. We may safely presume that early man wore the ape’s livery. How has man become, comparatively speaking, a nude animal. Wo obtain some light on this problem by noting the fact that the young of anthropoid apes, six weeks bclore birth, are as regards a hairy covering, exactly in’the same condition as new-born children. The hair on their scalps is long, but that on the rest of their bodies is an almost invisible down. Somehow, Nature has succeeded in bringing about the nude condition of the body by arresting hail growth in our bodies at the stage which is reached hy anthropoid apes some time before birth. When a useless structure such as a. hairy covering is to be got rid of, Nature does not pursue the extravagant method of allowing it to grow up and then sweeping it away, but nips it at once in the bml stage. This liudencss of the human body had become one of the great factors in making it possible to regulate the temperature by artificial clothing, and •thus to be able to find a habitation in almost every part oi tig' globe. HUMAN TAILS NOT UNKNOWN. Surgeons, in examining recruits for war purposes, had been surprised to find that traces of an outward tail were commoner than had been supposed. Every human embryo in the sixth week of development has a free projecting tail, which in point of form and size is similar to that possessed hv an embryo monkey. Rut towards the end of the second month of development, while the monkey’s tail continues to form new joints and to grow in length, the Human tail shrinks, withers, and disappears below the surface—a dimple on the skin marking the point at which the free end of the tail becomes submerged. Children born with tails are those in which the embryo submergence fail to occur. The loss of the tail is not a human prerogative; the tail disappears just in the same way in the embryo of gorillas, chimpanzees, orangs, and gibbons—indeed, in all the ape-like stork to which man is linked by a

great number of structural resemblances. Long before the human form began its evolution the tail bail already become a mere matter of history! The tail was lost long before man came on the scene. It disappeared when the anthropoid type of man’s ancestry gained a place in the world. In the body of an embryo, as in a : city, concluded the lecturer, there was a continual struggle going on between the reformers and the die-hards. In the embryonic body it was necessary to suppose that there was a continuous struggle between the various departments regulating development and growth. In this struggle useless structures like the tail were starved out. The struggle for survival, recognised by Darwin as part of the machinery of evolution, was as true of the living units making up an embryo as it was of human communities. In both eases the struggle was regulated, in one case by legislation, in the other by chemical messengers or hormones.