THE EVOLUTION OF MAN.1

By Prof. G. ELLIOT SMITH, M. A., M. D., Ch. M., F. R. S.

THE SCOPE OF EVOLUTION.

In a recent address Lord Morley referred to "evolution" as "the most overworked word in all the language of the day;" nevertheless, he was constrained to admit that, even when discussing such a theme as history and modern politics, "we can not do without it.” But to us in this section, concerned as we are with the problems of man's nature and the gradual emergence of human structure, customs, and institutions, the facts of evolution form the very fabric the threads of which we are endeavoring to disentangle; and in such studies ideas of evolution find more obvious expression than most of us can detect in modern politics. In such circumstances we are peculiarly liable to the risk of "overworking" not only the word "evolution," but also the application of the idea of evolution to the material of our investigations.

My predecessor in the office of president of this section last year uttered a protest against the tendency, to which British anthropologists of the present generation seem to be peculiarly prone, to read evolutionary ideas into many events in man's history and the spread of his knowledge and culture in which careful investigation can detect no indubitable trace of any such influences having been at work.

I need offer no apology for repeating and emphasizing some of the points brought forward in Dr. Rivers's deeply instructive address; for his lucid and convincing account of the circumstances that had compelled him to change his attitude toward the main problems of the history of human society in Melanesia first brought home to me the fact, which I had not clearly realized until then, that in my own experience, working in a very different domain of anthropology on the opposite side of the world, I had passed through phases precisely analogous to those described so graphically by Dr. Rivers. He told

1 Address delivered before the Anthropological Section at the Dundee meeting of the British Associa tion for the Advancement of Science in September, 1912. Reprinted by permission from Nature, London, Sept. 26, 1912. It represents the address as it was delivered at the meeting; it is a somewhat condensed and rearranged form of that appearing in the association's reports.

us that in his first attempts to trace out "the evolution of custom and institution" he started from the assumption that "where similarities are found in different parts of the world they are due to independent origin and development, which in turn is ascribed to the fundamental similarity of the workings of the human mind all over the world, so that, given similar conditions, similar customs and institutions will come into existence and develop on the same lines." But as he became more familiar with the materials of his research he found that such an attitude would not admit of an adequate explanation of the facts, and he was forced to confess that he "had ignored considerations arising from racial mixture and the blending of cultures."

I recall these statements to your recollection now, not merely for the purpose of emphasizing the far-reaching significance of an address which is certain to be looked back upon as one of the most distinctive and influential utterances from this presidential chair, nor yet with the object of telling you how, in the course of my investigations upon the history of the people in the Nile Valley,' I also started out to search for evidences of evolution, but gradually came to realize that the facts of racial admixture and the blending of cultures were far more obtrusive and significant. My intention is rather to investigate the domain of anthropology in which unequivocal evolutionary factors have played a definite rôle; I refer to the study of man's genealogy, and the forces that determined the precise line of development his ancestors pursued and ultimately fashioned man himself.

I suppose it is inevitable in these days that one trained in biological ways of thought should approach the problems of anthropology with the idea of independent development as his guiding principle; but the conviction must be reached sooner or later, by every one who conscientiously, and with an open mind, seeks to answer most of the questions relating to man's history and achievements-certainly the chapters in that history which come within the scope of the last 60 centuries-that evolution yields a surprisingly small contribution to the solution of the difficulties which present themselves. Most of the factors that call for investigation concerning the history of man and his works are unquestionably the direct effects of migrations and the intermingling of races and cultures.

But I would not have you misunderstand my meaning. Nothing could be further from my intention than to question the reality of evolution, as understood by Charles Darwin, and the tremendous influence it is still exerting upon mankind. In respect of certain perils man may, perhaps, have protected himself from "the general operation of that process of natural selection and survival of the fittest

1 "The Ancient Egyptians," Harpers, 1911.

which, up to his appearance, had been the law of the living world" (Sir Ray Lankester); but it has been demonstrated quite definitely that man, in virtue of these very heightened powers, which, to some observers, seem to have secured him an immunity from what Sir Ray Lankester calls "nature's inexorable discipline of death," is constantly exposing himself to new conditions that favor the operations of natural selection, as well as other forms of "selection" to which his increased powers of intelligent choice and his subjection to the influences of fashion expose him.

It is not, however, with such contentious matters as the precise mode of operation of evolution at the present day that I propose to deal; nor yet with the discussion of when and how the races of mankind became specialized and differentiated the one from the other. It is the much older story of the origin of man himself and the first glimmerings of human characteristics amidst even the remotest of his ancestors to which I invite you to give some consideration to-day.

In a recently published book the statement is made that "the uncertainties as to man's pedigree and antiquity are still great, and it is undeniably difficult to discover the factors in his emergence and ascent." There is undoubtedly the widest divergence of opinion as to the precise pedigree; nevertheless, there seems to me to be ample evidence now available to justify us sketching the genealogy of man and confidently drawing up his pedigree as far back as Eocene timesa matter of a million years or so-with at least as much certainty of detail and completeness as in the case of any other recent mammal; and if all the factors in his emergence are not yet known, there is one unquestionable, tangible factor that we can seize hold of and examinethe steady and uniform development of the brain along a welldefined course throughout the primates right up to man-which must give us the fundamental reason for "man's emergence and ascent," whatever other factors may contribute toward that consummation.

What I propose to attempt is to put into serial order those vertebrates which we have reason to believe are the nearest relatives to man's ancestors now available for examination and to determine what outstanding changes in the structure of the cerebral hemispheres have taken place at each upward step that may help to explain the gradual acquirement of the distinctively human mental faculties, which, by immeasurably increasing the power of adaptation to varying circumstances and modifying the process of sexual selection, have made man what he is at present.

The links in the chain of our ancestry supplied by paleontology are few and of doubtful value if considered apart from the illumination of comparative anatomy.

1 J. A. Thomson and P. Geddes, “Evolution," 1912, p. 102.

Psychologists have formulated certain definite phases through which the evolution of intelligence must have passed in the process of gradual building up of the structure of the mind. The brain in a sense is the incarnation of this mental structure; and it seemed to me that it would be instructive, and perhaps useful, to employ the facts of the evolution of the brain as the cement to unite into one comprehensive story the accumulations of knowledge concerning the essential facts of man's pedigree and the factors that have contributed to his emergence, which have been gathered by workers in such diverse departments of knowledge as zoology and comparative anatomy, geology and paleontology, and physiology and psychology.

For it was the evolution of the brain and the ability to profit by experience, which such perfecting of the cerebral mechanism made possible, that led to the emergence of mammals, as I attempted to demonstrate in opening the discussion on the origin of mammals at the Portsmouth meeting last year; and from the mammalia, by a continuation of this process of building up the cerebral cortex, or, if you prefer it, the structure of the mind, was eventually formed that living creature which has attained the most extensive powers of profiting by individual experience.

The study of the brain and mind, therefore, should have been the first care of the investigator of human origins. Charles Darwin, with his usual perspicuity, fully realized this; but since his time the rôle of intelligence and its instruments has been almost wholly ignored in these discussions, or when invoked at all wholly irrelevant aspects of the problems have been considered.

There can be no doubt that this neglect of the evidence which the comparative anatomy of the brain supplies is in large measure due to the discredit cast upon this branch of knowledge by the singularly futile pretensions of some of the foremost anatomists who opposed Darwin's views in the discussions which took place at the meetings of the British Association and elsewhere more than 40 years ago.

Many of you no doubt are familiar with Charles Kingsley's delightful ridicule of these learned discussions in the pages of "Water Babies." The controversy excited by Sir Richard Owen's contention that the great distinctive feature of the human brain was the possession of a structure that used to be called the hippocampus minor was not unjustly the mark of his scathing satire.

The professor had even got up at the British Association and declared that apes had hippopotamus majors in their brains, just as men have. Which was a shocking thing to say; for, if it were so, what would become of the faith, hope, and charity of immortal millions? You may think that there are other more important differences between you and an ape, such as being able to speak, and make machines, and know right from wrong, and say your prayers, and other little matters of that kind; but that is only a 1 Discussion on the "Origin of Mammals" at the meetings of Section D (Brit. Assoc. Reports, 1911, p. 424).

child's fancy, my dear. Nothing is to be depended upon but the great hippopotamus test. If you have a hippopotamus major in your brain, you are no ape, though you had four hands, no feet, and were more apeish than the apes of all aperies. Always remember that the one true, certain, final, and all-important difference between you and an ape is that you have a hippopotamus major in your brain and it has none. If a hippopotamus was discovered in an ape's brain, why, it would not be one, you know, but something else.

The measure of the futility of the contention thus held up to scorn can be more justly realized now; for some years ago I discovered that the feature referred to in Kingsley's burlesque phrase, "hippopotamus major," which Owen claimed to be distinctive of the human brain, and Huxley maintained was present also in apes, is quite a primitive characteristic, and the common property of the mammalia in general. This illustration of the nature of the discussions which distracted attention from the real problems, although the most notorious one, is unfortunately characteristic of the state of affairs that prevailed when prejudice blinded men's eyes to the obvious facts that were calling so urgently for calm investigation.

MAN'S PEDIGREE.

No one who is familiar with the anatomy of man and the apes can refuse to admit that no hypothesis other than that of close kinship affords a reasonable or creditable explanation of the extraordinarily exact identity of structure that obtains in most parts of the bodies of man and the gorilla. To deny the validity of this evidence of near kinship is tantamount to a confession of the utter uselessness of the facts of comparative anatomy as indications of genetic relationships, and a reversion to the obscurantism of the dark ages of biology. But if anyone still harbors an honest doubt in the face of this overwhelming testimony from mere structure, the reactions of the blood will confirm the teaching of anatomy; and the susceptibility of the anthropoid apes to the infection of human diseases, from which other apes and mammals in general are immune, should complete and clinch the proof for all who are willing to be convinced.

Nor can anyone who, with an open mind, applies similar tests to the gibbon refuse to admit that it is a true, if very primitive, anthropoid ape, nearly related to the common ancestor of man, the gorilla, and the chimpanzee. Moreover, its structure reveals indubitable evidence of its derivation from some primitive Old World or catarrhine monkey akin to the ancestor of the langur, the sacred monkey of India. It is equally certain that the catarrhine apes were derived from some primitive platyrrhine ape; the other, less modified, descendants of which we recognize in the South American monkeys of the present day; and that the common ancestor of all these primates was a lemuroid nearly akin to the curious little spectral tarsier, which still haunts the forests of Borneo, Java, and the neighboring