ANIMAL EVOLUTION

Evening Star, Issue 19615, 22 July 1927, Page 3

ANIMAL EVOLUTION

LECTURE BY DR BENHAM The physics lecture room of the University was crowded last evening, when the second of the series of lectures on evolution was delivered by Dr W. 15. Benham, professor of biology. The tact that many enthusiasts were only too pleased to listen in a standing posture to the lecture is sufficient proof of the interest tho subject is creating, and-is also a tribute to Dr Denham’s ability to handle it. Dr Dedham staled that he was not going to concern himself with any theories of evolution such as those associated with tho mimes of Darwin, Lamarck, or Weissman. His purpose was to put forward some of the'tacts upon which any theory had to bo based, for if Darwinism or Lamarckism or any other theory were proved to be unsound the evolution of tho organic world would remain as an uncontrovertible fact. In every plant and animal organic compounds were mixed together in various proportions to form a material known as protoplasm, which was the fundamental and characteristic material of which all living things consisted. The vast majority of animals were composed of myriads of units or cells, arranged in groups to form tissues, which differed from one another only in their special qualities, so as to serve different purposes in the body, such as flesh (.that was, muscle), blood, nerve, bone, tendons, and so on. Chemists had been able to make in their laboratories such things as syn'thetic sugar, synthetic indigo, synthetic thyroxin, and several other organic substances, but up to the present proteins had not be made by them, and it was extremely unlikely that any chemist would be able to make that particular mixture of proteins, sugars, and fats which constituted protoplasm, and to endow it with life, for scientists were quite ignorant as to the constitution of these combinations. They did not know the precise variety or number of proteins needed to produce protoplasm. The problem of organic evolution was the explanation of how the great variety of existing species had come into being, in the case of animals it was not the thing itself that underwent those changes that had brought about evolution of species, but the changes affected successive generations of individuals. They had here a totally new phenomenon, or rather two phenomena—namely , reproduction and heredity, in the case of organic evolution, any change that might take place in the individual would be handed on to tho offspring, and it might be increased, if it were beneficial in any way in the battle for life in successive generations, to such a degree that the species might be so altered in structure and in other ways as to be entirely dissiiuiljii' to the original ancestor that a new species would have arisen. The lion, tiger, leopard, jaguar, puma, and cat were all species of one genus, but they differed in size, color of coat, weight, ferocity, and so on. There was reason to believe from the study of fossils that all these species had descended from one ancestral species, whoso successive offspring had diverged more or loss from it and from one another, undergoing slightly different modifications of structure in relation to changes in the physical world. To put the whole thing briefly, organic evolution implied descent from a common ancestor, with modifications of structure in successive generations and along different lines. He proposed to state some ol the evidence on which biologists believed that the present condition of the organic world had resulted from evolution. This evidence was drawn from a variety of biological sources, aiid tho interesting and important fact about it was that the evidence derived from the study ol anyone aspect ol biology- agreed with that nulled from other aspects, ami there was no contradiction ol one by another. Ho would, however, have time to present evidence from only three-sources —(11 the study of comparative anatomy, that was file comparison of the structure in existing groups ol animals with one another; (2) tho study ol embryology or the process by- which an egg developed into an individual; (2) palaeontology, which was ilio study of those animals which lived in past limcifand whose remains had been preserved as fossils in the rocks of the earth’s crust.

By menus ol' lantern slides Dr Benhain proceeded to explain points of similarity in various mammals and to show how changes had gradually taken place in the course of time. Jt was a rather interesting fact, said Dr Denham, that life commenced in the sea. and at an early age both plants and animals mado their appearance. One of the most interesting events was the invasion of the land—the assumption of a terrestrial habit. Jrlo had not time to go into matters of detail, hut from the fossilised animals they could trace the history. The could trace the tirst amphibian back to a group ol fishes, and they could trace the earliest reptiles back to their amphibian ancestors; and this could he done with a very great degree of surety. There was a” certain amount of evidence that just as birds wore evolved or developed from reptiles, so were mammals, though that evidence was not so clcai - as in the case of birds. One reason why the mammals succeeded when once they commenced to develop, and thus ousted the reptiles, lay, no doubt, in their much larger brain and in its great differentiation in structure allowing them to execute a greater variety of movements and also to develop a greater range of mental processes. It was a question of brain versus brawn, and brain won. Dr Benham used trie facts about the elephant to illustrate the evolution of a present-day animal, and proceeded to deal with lemurs, monkeys, apes. etc. In summarising, I)r Bonham said that, although he did not intend to discuss the various theories as to how evolution had come about, he could not retrain from contradicting a rather v/idqlv-diffuscd idea that Darwinism was dead. He said that Darwin’s theory of the origin of species by natural selection 'was as strongly held today as ever it was as the main factor in evolution. Jl was true that a number of subsidiary factors had been put forward in recent years, as was only natural, in view of tho largo amount of research and thought by a host of naturalists. Tie wished also to state that Mendelism, which was so much spoken of and written about in magagines as if it had displaced Darwinism, was merely a method and theory or heredity. Jt was not a theory of evolution, but it shed much light on heredity, which was at the base of every theory of evolution. It could not displace Darwinism, for it dealt with only a part of the problem. Tho facts about the development of the animal kingdom were incontrovertible, and the only explanation of these facts that appealed io the intellect as being reasonable was that tho present condition of the organic world was the result of some process, which was termed organic evolution. Dr Benham was a corded a hearty vote of thanks for his lecture.