human varieties, and canine varieties, bearing the same characteristics as at the present day, there is nothing to disturb this conclusion; for, on the one hand, a period of three thousand years is coming to be regarded as not including a very large part of man's existence on the earth; and, on the other hand, such a fact only proves the persistency which a type may possess when fully developed, and is of very doubtful avail to show the originality of the type. Something analogous is to be seen in language. The speech of our rude Germanic ancestors of the same remote period, had we authentic record of it, would beyond question be found to have possessed already a general character clearly identifying it with Germanic tongues still existing, and sharply sundering it from Greek, from Slavonic, from Celtic, and all the other Indo-European branches; yet we do not doubt that the Germanic type of speech is a derived, a secondary one. In settling all these controverted points, in distinguishing between original diversity and subsequent variation, in establishing a test and scale for the possibilities and the rate of physical change, the physical ethnologist will need all the assistance which historical investigations of every kind can furnish him; and the greater part must come to him from the student of language.
As the Indo-European family of language is that one of which the unity, accompanying a not inconsiderable variety of physical type in the peoples who speak its dialects, is most firmly established, and as therefore it may naturally be regarded as furnishing a prominent illustration of the bearing of linguistic conditions on physical inquiries into the history of man, it is perhaps worth our while to refer to a theory respecting Indo-European speech which has found of late a few supporters of some note and authority, and which, if accepted, would altogether deprive it of ethnological value. The assertion, namely, is put forth, that the apparent unity of the languages of this family is not due to a prevailing identity of descent in the nations to which they belong, but to the influence of some single tribe, whose superior character, capacity, and prowess enabled it to impose its linguistic usages on distant and diverse races.
