September 26, 1912] 



NATURE 



12- 



that at each stage in the migrations of man's ances- 

 tors, menotyphlous, prosimian, platyrrhine, catarrhine 

 and anthropoid, the unprogressive members remained 

 somewhere in the neighbourhood of the home of their 

 immediate ancestors, and that those which wandered 

 into new surroundings had to struggle for their foot- 

 ing, and as the result of this striving attained a higher 

 rank. 



Other slides were shown to demonstrate the fact that 

 in this series of primates there was a steady develop- 

 ment of the brain— expansion and differentiation of the 

 visual, tactile and auditory centres, and development 

 of the meeting territory between them ; a marked 

 growth and specialisation of the motor centres, and the 

 power of skilled movements, especially of the hands 

 and fingers; and a regular expansion of the prefrontal 

 area — along the lines marked out once for all when 

 the first primate was formed from some menotyphlous 

 progenitor.] 



Thus the outstanding feature in the gradual evolu- 

 tion of the primate brain is a steady growth and 

 differentiation of precisely those cortical areas which 

 took on an enhanced importance in the earliest 

 primates. 



So far in this address I have been delving into the 

 extremely remote, rather than the nearer, ancestry of 

 man, because I believe the germs of his intellectual 

 preeminence were sown at the very dawn of the 

 Tertiary period, when the first anaptomorphid began 

 to rely upon vision rather than smell as its guiding 

 sense. In all the succeeding ages since that remote 

 time the fuller cultivation of the means of profiting 

 by experience, which the tarsioid had adopted, led 

 to the steady upward progression of the primates. 

 From time to time many individuals, finding them- 

 selves amidst surroundings which were thoroughly 

 congenial and called for no effort, lagged behind ; 

 and in Tarsius and the lemurs, the New World 

 monkevs, the Old ^^'orld monkeys, and the anthro- 

 poids, not to mention the extinct forms, we find pre- 

 served a series of these laggards which have turned 

 aside from the highway which led to man's estate. 



The primates at first were a small and humble folk, 

 who led a quite unobtrusive and safe life in the 

 branches of trees, taking small part in the fierce com- 

 petition for size and supremacy that was being waged 

 upon the earth beneath them by their carnivorous, 

 ungulate, and other brethren. But all the time they 

 were cultivating that equable development of all their 

 senses and limbs, and that special development of the 

 more intellectually useful faculties of the mind which, 

 in the long run, were to make them the progenitors 

 of the dominant mammal — the mammal which was to 

 obtain the supremacy over all others, while still re- 

 taining much of the primitive structure of limb that 

 his competitors had sacrificed. It is important, then, 

 to keep in mind that the retention of primitive char- 

 acters is often to be looked upon as a token that their 

 possessor has not been compelled to turn aside from 

 the straight path and adopt protective specialisations, 

 but has been able to preserve some of his primitive- 

 ness and the plasticity associated with it, precisely 

 because he has not succumbed or fallen away in the 

 struggle for supremacy. It is the wider triumph of 

 the individual who specialises late, after benefiting by 

 the many-sided experience of early life, over him who 

 in youth becomes tied to one narrow calling. 



In many respects man retains more of the primitive 

 characteristics, for example, in his hands, than his 

 nearest simian relatives ; and in the supreme race of 

 mankind many traits, such as abundance of hair, 

 persist to suggest pithecoid aflinities, which have been 

 lost by the more specialised negro and other races. 

 Those anthropologists who use the retention of 

 primitive features in the Nordic European as an argu- 



No. 2239, VOL. go] 



ment to exalt the negro to equality with him are 

 neglecting the clear teaching of comparative anatomy, 

 that the persistence of primitive traits is often a sign 

 of strength rather than of weakness. This factor runs 

 through the history of the whole animal kingdom." 

 Man is the ultimate product of that line of ancestry 

 which was never compelled to turn aside and adopt 

 protective specialisation either of structure or mode 

 of life, which would be fatal to its plasticity and power 

 of further development. 



Having now examined the nature of the factors that 

 have made a primate from an insectivore and have 

 transformed a tarsioid prosimian into an ape, let us 

 turn next to consider how man himself was fashioned. 



Tfte Origin of Man. 



It is the last stage in the evolution of man that 

 has always excited chief interest and has been the 

 subject of much speculation, as the addresses of my 

 predecessors in this presidency bear ample witness. 



These discussions usually resolve themselves into the 

 consideration of such questions as whether it was the 

 growth of the brain, the acquisition of the power of 

 speech, or the assumption of the erect attitude that 

 came first and made the ape into a human being. 

 The case for the erect attitude was ably put before the 

 Association in the address delivered to this section by 

 Dr. Munro in 1893. He argued that the liberation 

 of the hands and the cultivation of their skill lay at 

 the root of man's mental supremacy. 



If the erect attitude is to explain all, why did not 

 the gibbon become a man in Miocene times? The 

 whole of my argument has aimed at demonstrating 

 that the steady growth and specialisation of the brain 

 has been the fundamental factor in leading man's 

 ancestors step by step right upward from the lowly 

 insectivore status, nay, further, through every earlier 

 phase in the evolution of mammals — for man's brain 

 represents the consummation of pr:c'.s?ly those factors 

 which throughout the vertebrata have brought their 

 possessors to the crest of the wave of progress. _ But 

 such advances as the assumption of the erect attitude 

 are brought about simply because the brain has made 

 skilled movements of the hands possible and of definite 

 use in the struggle for existence : yet once such a stage 

 has been attained the very act of liberating the hands 

 for the performance of more delicate movements opens 

 the way for a further advance in brain development 

 to make the most of the more favourable conditions 

 and the greater potentialities of the hands. 



It is a fact beyond dispute that the diver- 

 gent specialisation ' of the human limbs, one 

 pair for progression, and the other for pre- 

 hension and the more delicately adjusted skilled 

 action, has played a large pan in preparing the 

 way for the ernergence of the distinctively human 

 chaVacteristics ; but it would be a fatal mistake un- 

 duly to magnifv the influence of these developments. 

 The most primitive living primate, the spectral tarsier, 

 frequently assumes the erect attitude, .and uses its 

 hands for prehension rather than progression in many 

 of its acts, and many other lemurs, such as the In- 

 drisina of Madagascar, can and do walk erect. 



In the remote Oligocene, a catarrhine ape, nearly 

 akin to the ancestors of the Indian sacred monkey, 

 Semnopithecus, became definitely specialised in struc- 

 ture in adaptation for the assumption of the erect 

 attitude; and this type of early anthropoid has per- 

 sisted with relatively slight modifications in the gib- 

 bon of the present day. Rut if the earliest gibbons 

 were already able to walk upright, how is it, one 

 might ask, that they did not begin to use their hands, 

 thus freed from the' work of progression on the earth, 

 for skilled work, and at once before men? The 



11 •' The Brain in the EdentaU," Trans. Linn. Soc, 1899. 



