456 POPULAR SCIENCE MONTHLY 



ventures to assert that man and all other living creatures are one with 

 the mind-stuff of the inorganic world — and this, I believe, is only the 

 logical extension of the genetic and mechanistic hypotheses. However 

 this may be, science holds that human structure is animal structure, 

 and that human lives are biological phenomena. 



Man is structurally inferior in many respects to some of his zoolog- 

 ical relatives — he is a degenerate, indeed, in many parts of the alimen- 

 tary, muscular and skeletal systems — yet he finds in the higher devel- 

 opment of his nervous system an advantage that offsets the weaknesses 

 of his constitution elsewhere. He holds his supreme place by virtue 

 only of superior and more effective control of his organization. 



Behind their seeming structural differences, only one real distinc- 

 tion can be found to separate man from the apes — the higher develop- 

 ment of the brain. The erect posture, the correlated modifications of 

 skeletal and muscular structures, and apparently the powers of speech 

 and reason, seem to be dependent upon the enlargement of this organ, 

 which, so to speak, has pushed the face around under the brain-case. 

 Therefore he who would be 6 ^vftncoKoc — he who looks ahead — must 

 needs stand erect in order to prevent his eyes from looking straight 

 into the ground. But the most careful analysis has so far failed to 

 detect any essential differences in either structural or functional 

 respects between the human brain and the corresponding organs of the 

 higher apes. In brief, then, differences in degree and not in kind or 

 category seem to distinguish man from the apes — as far as science goes. 



Moreover, the human body is a veritable museum of rare and inter- 

 esting relics of antiquity — the useless vestiges and rudiments of struc- 

 tures that are more developed in other animals. The complete coat 

 of hair of the embryo, the disappearing thirteenth rib, the ape-like 

 and transitory clasping muscle of the new born infant's hand, the 

 curvature of the lower limb and the hand-like foot of the embryo, these 

 and scores of other characters are mutely eloquent witnesses to the 

 past history of change that has brought man to his present place in 

 nature. Embryology gives a vast amount of additional independent 

 testimony. For like all embryo mammals and birds and reptiles, the 

 human embryo possesses gill-slits, and fish-like heart and brain. Above 

 all it begins life as a single cell. Zoology asks : What can these things 

 mean, if they do not mean evolution and a common ancestry with other 

 forms ? The objection that no one has ever seen a one-celled organism 

 evolve into a many-celled one, or into a fish or an ape, or into a man, 

 the zoologist answers by placing upon the table the evidence that a 

 single-cell, the human egg, actually does compass the whole history in 

 becoming the almost inconceivably complex adult organism. The 

 process can take place for it does take place. Paleontology also pre- 

 sents evidence relating to the history of our species, as the third support 



