POPULAR SCIENCE-

Star (Christchurch), Issue 19268, 3 January 1931, Page 19 (Supplement)

POPULAR SCIENCE-

' (By

J. J. S. CORNES,

THE STORY OF MAN. No one thinks less of Sir Isaac Newton because he was born as a very puny infant, anrl no one should think less of the human race because it sprang from a stock of arboreal mammals. There is no doubt as to man’s apartness from the rest of creation when he is seen at his best, “a little lower than the angels, crowned with glory and honour.” Nevertheless, all the facts point to his affiliation to the stock to which monkeys and apes also belong. Not, indeed, that any man is descended from any living ape or monkey; it is rather that he and they have sprung from a common ancestry—are branches of the same stem. The story of animal life in past ages, as revealed by geological study, proves beyond question the fact of evolution —i.e., the development of the innumerable kinds of animals from pre-existing forms—so that modern schemes of classification take the form of genealogical trees. Man is a backboned animal belonging to the class of mammals, distinguished by the possession of a hairy covering, hot blood, milk-produc-ing glands, and a relatively welldeveloped brain. There can be no doubt that mammals took origin from reptiles, a class that w T as dominant on land —and even invaded sea and air during the geological middle ages, the Mesozoic Period, toward the end of which they rapidly declined. The rise of mammals —and also. of birds—was primarily the result of improvements in the structure of the heart, in which the pure and impure blood became completely separated, so that the whole of the body was supplied with pure (oxygenated) blood, resulting in increased activity and rendering possible the maintenance of a constant and relatively high temperature, greatly conducing to such activity. This was an immense advance upon reptiles, with bodies nourished by “mixed,” i.e., imperfectly oxygenated, blood, of which the temperature varied with that of the surroundings, so that cold weather meant sluggishness. It followed that mammals, largely independent of climate, gained a great advantage over their rivals, and this

g m ® EB SE HI S 3 EE) IS H M BE S S 3 EE ® ® El HI IS, was confirmed by increase in size of the brain, which meant enhanced intelligence. During Merozoic times the mammals w-ere comparatively few and feeble, but from the dawn of the next, or Tertiary, epoch, they became the rulers of the land, and also began to invade the sea (seals, whales, etc.) and the air (bats). Examination of the geological record demonstrates that many groups of ani mals, small and large, have completely died out, this being particularly noticeable as regards Merozoic reptiles. It is now generally believed that such extinction is commonly the penalty of over-specialisation, involving the loss of primitive characters, in other words, a loss of adaptability to changing circumstances. This is the same kind of thing that makes the solution of some unemployment problems so difficult at present. An over-specialised man has become an expert in doing one sort of thing, and when out of work is less able to adapt himself to new tasks than the “handy man,” who can do all sorts of things sufficiently, though not supremely, well. The Primates. Mammals having vanquished reptiles, specialised along all sorts of lines, and many of them became extinct in the struggle for existence with one another. The branch with which we are here concerned is the order Primates, in which are included the highest mammals—lemurs monkeys, apes, and men. The origin of this order and the course of its evolution have recently been dealt with by Elliot Smith in a brilliant and fascinating way (Evolution of Man, 1924) and some of his conclusions here follow. They furnish an in- 1 valuable “working hypothesis,” but this will probably be modified by subsequent research, as in the case of scientific theories in general. Such theories are best held “lightly” until proved up to the hilt.

B.A. B.Sc.;

Remembering what ha* been said of “primitive” character, we shall not be surprised to hear that the monkey order (Primates) apparently took origin from the Insectivora, a lowly group of mammals possessing that plasticity which lends itself to the moulding forces of evolution, with the production of characters suited to new surroundings. Mammals gained their dominant position by improvement in their brains, and toward the end of the Mesozoic period the Insectivorea made further advances in that respect, and originated the primitive stock from which lemurs, monkeys and ultimately men, have descended. Insectivores were, to begin with, small ground animal*, as many of them (shrews, hedgehogs, moles) are to this day, and their master-sense was that of smell. Some of them, however, took to climbing, and were modified into the group of treeshrews, w’hich still survive in the Malay regipn. This new wa}' of life necessitated improvements in vision and touch, associated with increased agility and more skilful movements, and at the same time the brain increased in size and complexity, and a higher standard of intelligence was attained. Still further advances on the same line* brought into existence the ancestral stock of lemurs, monkeys and men. Further evolution then took place, probably in the area now partly occupied by central America, the lemur* splitting off as a side branch, and the main stock specialising into a somewhat higher group (the Tarsioids), of which the little Spectre Tarsier of the East Indies is the sole survivor. This further advance seems to have been mainly due to the inception of “ stereoscopic ” vision, i.e., the co-operation of both eyes in looking at things, with resulting improvements in the brain. Progress on this line gave rise to monkey-like creatures. We learn from geology that there have been great changes in the distribution of land and water, and that when lemurs and monkeys were being involved in Central America, the New and the Old Worlds were connected by land bridges, where now is the Atlantic Ocean. While some of the primitive monkeys wandered into South America to establish the relatively low group of New World monkeys, others, and also

IHlH[*lll!aaE]®E]@®E!ElEiEl®Ei@E3 the lemurs, gradually made their way across the land-bridges into the Old World, undergoing many changes during their long journey. In some of the geological deposits of Egypt (Fayum) we find the fossil remains of the improved type to which the name of Old World monkeys is given, and also the progenitors of the still higher man-like apes. The latter spread over most parts of the Old World, increasing in size and developing larger brains, while many different types, probably including the immediate ancestors of man, developed in North India (Sivalik area). The existing man-like apes—gibbons, orangs, chimpanzees, and gorillas successively came into existence as side-branches of the main tree of descent. The earliest fossil remains that can be regarded as belonging to man have been found in the last stage (Pleistocene) of the Tertiary epoch and furnish proof of (1) the possession of a relatively large brain; (2) the existence of that part of the brain associated with the power of articulate speech. The acquisition of this power marked the transition from brute to man, and enormously increased his ability to profit by experience. The assumption of the erect attitude, though not peculiar to man, has had far-reaching consequences in his evolution. It has liberated the upper limbs for delicate manipulation, and this has stimulated further specialisations in the brain. We do not yet know in what part of the Old World the first men were evolved, but tropical Africa seems most likely. I Naturalists have exposed the pit whence man has been digged and the rock whence he has been hewn, and it is surely a heartening encouragement to know that it is an ascent, not a descent, that we have behind us. (To be Continued Next Saturday.) 1