It is clear at least that there were great movements of population, much mingling of types and commercial interchange of products, so that we have the constant conditions of advance. A last invasion seems to have taken place some two or three thousand years before the Christian era, when the Aryans overspread Europe. After all the controversy about the Aryans it seems clear that a powerful race, representing the ancestors of most of the actual peoples of Europe and speaking the dialects which have been modified into the related languages of the Greeks, Romans, Germans, Celts, Lithuanians, etc., imposed its speech on nearly the whole of the continent. Only in the Basques and Picts do we seem to find some remnants of the earlier non-Aryan tongues. But whether these Aryans really came from Asia, as it used to be thought, or developed in the east of Europe, is uncertain. We seem justified in thinking that a very robust race had been growing in numbers and power during the Neolithic Age, somewhere in the region of South-east Europe and Southwest Asia, and that a few thousand years before the Christian Era one branch of it descended upon India, another upon the Persian region, and another overspread Europe. We will return to the point later. Instead of being the bearers of a higher civilisation, these primitive Aryans seem to have been lower in culture than the peoples on whom they fell. The Neolithic Age had meantime passed into the Age of Metal. Copper was probably the first metal to be used. It is easily worked, and is found in nature. But the few copper implements we possess do not suggest a "Copper Age" of any length or extent. It was soon found, apparently, that an admixture of tin hardened the copper, and the Bronze Age followed. The use of bronze was known in Egypt about 4800 B.C. (Flinders Petrie), but little used until about 2000 B.C. By that time (or a few centuries later) it had spread as far as Scandinavia and Britain. The region of invention is not known, but we have large numbers of beautiful specimens of bronze work--including brooches and hair-pins--in all parts of Europe. Finally, about the thirteenth century B.C., we find the first traces of the use of iron. The first great centre for the making of iron weapons seems to have been Hallstatt, in the Austrian Alps, whence it spread slowly over Europe, reaching Scandinavia and Britain between 500 and 300 B.C. But the story of man had long before this entered the historical period, to which we now turn. CHAPTER XXI. EVOLUTION IN HISTORY