ch give us an African, a European, and an
American subspecies.

It is possible that more extended researches may enable ethnographers to
map out, in this sense, the distribution of our species; but the secular
alterations in meteorologic conditions, combined with the migratory
habits of most early communities, must greatly interfere with a rigid
application of these principles in ethnography.

The historic theory of "centres of civilisation" is allied to that of
ethno-geographic provinces. The stock examples of such are familiar. The
Babylonian plain, the valley of the Nile, in America the plateaus of
Mexico and of Tiahuanuco are constantly quoted as such. The geographic
advantages these situations offered--a fertile soil, protection from
enemies, domesticable plants, and a moderate climate--are offered as
reasons why an advanced culture rapidly developed in them, and from them
extended over adjacent regions.

Without denying the advantages of such surroundings, the most recent
researches in both hemispheres tend to reduce materially their
influence. The cultures in question did not begin at one point and
radiate from it, but arose simultaneously over wide areas, in different
linguistic stocks, with slight connections; and only later, and
secondarily, was it successfully concentrated by some one tribe--by the
agency, it is now believed, of cognatic rather than geographic aids.

Assyriologists no longer believe that Sumerian culture originated in the
delta of the Euphrates, and Egyptologists look for the sources of the
civilization of the Nile Valley among the Libyans; while in the New
World not one but seven stocks partook of the Aztec learning, and half a
dozen contributed to that of the Incas. The prehistoric culture of
Europe was not one of Carthaginians or Phoenicians, but was
self-developed.

2. Slavery Defined[225]

In most branches of knowledge the phenomena the man of science has to
deal with have their technical names, and, when using a scientific
term, he need not have regard to the meaning this term conveys in
ordinary language; he knows he will not be misunderstood by his
fellow-scientists. For instance, the Germans call a whale _Wallfisch_,
and the English speak of shellfish; but a zoologist, using the word
fish, need not fear that any competent person will think he means whales
or shellfish.

In ethnology the state of things is quite different. There are a few
scientific names bearing a definite