mcgee] the trend of human PROGRESS 4*7
creature of a psychologic moment, while the career of a life- time is shaped by a few critical hours or days ; and it seems equally certain, once attention is directed to the subject, that the course of demotic modification of the human organism is to be traced in the succession of critical instants of supreme intensity in action and passion. The canyon-cutting river ripples idly over its bed without carving a line during the eleven months of low water, and then saws through a foot of rock during the month of freshet ; and so the stream of human activity ripples merrily but idly until crises compel the action by which the mind is molded and the body shaped — when conation becomes the key-note of progress, as our associate Ward has shown.
With due appreciation of the paramount role of concentrated intensity of action in shaping the course of human development, it seems possible to explain, at least provisionally, the apparently sudden and complete transformation of man as he left the plane of the brute, and his continued and increasingly rapid develop, ment on the higher plane. The differences between man and ape which appeal to all observers (save those whose trained vision is fixed on structural homologies alone) are too many for easy reckoning; they include the erect attitude, the practically hair- less skin save where a more luxuriant pilary coat serves esthetic function, the expressive countenance susceptible alike of smiles and tears, the tool-using hand, and above all else the peculiar in- telligence enlivening the visage and directing the hand — attributes which indeed find their germ among lower animals, yet attain full development only in the highest of the series. For convenience, these and other attributes may be combined in somewhat general categories, (i) the erect attitude, (2) personal comeliness, (3) manual delicacy, and (4) capacity for intellectual choice of associates and mates.
Now, the distinctive characters of Pithecanthropus, erect yet almost simian in size and form of skull (and so marking a critical stage in development), support a previous view that the upright
AM. ANTH. N. S M I — 27
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