metry, deduced a special action of
mountains upon pigmentation on observing a prevailing increase of
blondness in Italy above the four-hundred meter line, a phenomenon which
came out as strongly in Basilicata and Calabria provinces of the south
as in Piedmont and Lombardy in the north.[63] The dark Hamitic Berbers
of northern Africa have developed an unmistakable blond variant in high
valleys of the Atlas range, which in a sub-tropical region rises to the
height of 12,000 feet. Here among the Kabyles the population is fair;
grey, blue or green eyes are frequent, as is also reddish blond or
chestnut hair.[64] Waitz long ago affirmed this tendency of mountaineers
to lighter coloring from his study of primitive peoples.[65] The
modification can not be attributed wholly to climatic contrast between
mountain and plain. Some other factor, like the economic poverty of the
environment and the poor food-supply, as Livi suggests, has had a hand
in the result; but just what it is or how it has operated cannot yet be
defined.[66]

[Sidenote: Difficulty of Generalization]

Enough has been said to show that the geographer can formulate no broad
generalization as to the relation of pigmentation and climate from the
occurrence of the darkest skins in the Tropics; because this fact is
weakened by the appearance also of lighter tints in the hottest
districts, and of darker ones in arctic and temperate regions. The
geographer must investigate the questions when and where deeper shades
develop in the skins of fair races; what is the significance of dark
skins in the cold zones and of fair ones in hot zones. His answer must
be based largely on the conclusions of physiologists and physicists, and
only when these have reached a satisfactory solution of each detail of
the problem can the geographer summarize the influence of environment
upon pigmentation. The rule can therefore safely be laid down that in
all investigation of geographic influences upon the permanent physical
characteristics of races, the geographic distribution of these should be
left out of consideration till the last, since it so easily
misleads.[67] Moreover, owing to the ceaseless movements of mankind,
these effects do not remain confined to the region that produced them,
but pass on with the wandering throng in whom they have once developed,
and in whom they endure or vanish according as they prove beneficial or
deleterious in the new habitat.

[Sidenote: Psychical eff