460 
DARWINISM 
CHAP. 
are absent. 1 There remains only the great Euro-Asiatic con¬ 
tinent ; and its enormous plateaux, extending from Persia 
right across Tibet and Siberia to Manchuria, afford an area, 
some part or other of which probably offered suitable con¬ 
ditions, in late Miocene or early Pliocene times, for the develop¬ 
ment of ancestral man. 
It is in this area that we still find that type of mankind — 
the Mongolian—which retains a colour of the skin midway 
between the black or brown-black of the negro, and the ruddy 
or olive-white of the Caucasian types, a colour which still 
prevails over all Northern Asia, over the American continents, 
and over much of Polynesia. From this primary tint arose, 
under the influence of varied conditions, and probably in 
correlation with constitutional changes adapted to peculiar 
climates, the varied tints which still exist among mankind. If 
the reasoning by which this conclusion is reached be sound, and 
all the earlier stages of man’s development from an animal 
form occurred in the area now indicated, we can better under¬ 
stand how it is that we have as yet met with no traces of the 
missing links, or even of man’s existence during late tertiary 
times, because no part of the world is so entirely unexplored 
by the geologist as this very region. The area in question is 
sufficiently extensive and varied to admit of primeval man 
having attained to a considerable population, and having 
developed his full human characteristics, both physical and 
mental, before there was any need for him to migrate beyond 
its limits. One of his earliest important migrations was 
probably into Africa, where, spreading westward, he became 
modified in colour and hair in correlation with physiological 
changes adapting him to the climate of the equatorial low¬ 
lands. Spreading north-westward into Europe the moist and 
cool climate led to a modification of an opposite character, and 
thus may have arisen the three great human types which still 
exist. Somewhat later, probably, he spread eastward into 
North AVest America and soon scattered himself over the 
whole continent; and all this may well have occurred in 
early or middle Pliocene times. Thereafter, at very long 
intervals, successive waves of migration carried him into every 
1 For a full discussion of this question, see the author’s Geographical 
Distribution of Animals, vol. i. p. 285. 
