460 DARWINISM chap. 



are absent.^ 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 a ea, 

 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 Avhich 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 Avas 

 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 -West America and soon scattered himself over the 

 Avhole 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 



^ For a full discussion of tliis question, see the author's Geographical 

 Distribution of Animals, vol. i. p. 285. 



