apes, but all the higher quadrumana are
absent.[227] There remains only the great Euro-Asiatic continent; 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 conditions, in late Miocene or early Pliocene
times, for the development 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 understand 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 lowlands.
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 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 part of the habitable world,
and by conquest and intermixture led ultimately to that puzzling
gradation of types which the ethnologist in vain seeks to unravel.

_The Origin of the M