Still more obscure is the problem of their racial affinity. The obliquely set eyes of the figures in the earlier reliefs, due mainly to an ignorance of perspective characteristic of all primitive art, first suggested the theory that the Sumerians were of Mongol type; and the further developments of this view, according to which a Chinese origin is to be sought both for Sumerian roots and for the cuneiform character, are too improbable to need detailed refutation. A more recent suggestion, that their language is of Indo-European origin and structure,[59] is scarcely less improbable, while resemblances which have been pointed out between isolated words in Sumerian and in Armenian, Turkish, and other languages of Western Asia, may well be fortuitous. With the Elamites upon their eastern border the Sumerians had close relations from the first, but the two races do not appear to be related either in language or by physical characteristics. The scientific study of the Sumerian tongue, inaugurated by Professors Zimmern and Jensen, and more especially by the work of M. Thureau-Dangin on the early texts, will doubtless lead in time to more accurate knowledge on this subject; but, until the phonetic elements of the language are firmly established, all theories based upon linguistic comparisons are necessarily insecure.
In view of the absence of Semitic influence in Sumer during the earlier periods, it may be conjectured that the Semitic immigrants did not reach Babylonia from the south, but from the north-west, after traversing the Syrian coast-lands. This first great influx of Semitic nomad tribes left colonists behind them in that region, who afterwards as the Amurru, or Western Semites, pressed on in their turn into Babylonia and established the earliest independent dynasty in Babylon. The original movement continued into Northern Babylonia, and its representatives in history were the early Semitic kings of Kish and Akkad. But the movement did not stop there; it passed on to the foot of the Zagros hills, and left its traces in the independent principalities of Lulubu and Gutiu. Such in outline appears to have been the course of this early migratory movement, which, after colonizing the areas through which it passed, eventually expended itself in the western mountains of Persia. It was mainly through contact with the higher culture of the Sumerians that the tribes which settled in Akkad were enabled later on to play so important a part in the history of Western Asia.