An area conforming to these requirements is offered by the forests and plains of eastern Germany, Poland and Russia. It was here that the Proto-Nordic type evolved and here their remnants are found. They were protected from Asia on the east by the then almost continuous water connections across eastern Russia between the White Sea and the old Caspian-Aral Sea. During the last glacial advance (known as the Würm) which, like the preceding glaciations, is believed to have been a period of land depression, the White Sea extended far to the south of its present limits, while the enlarged Caspian Sea, then and long afterward connected with the Sea of Aral, extended northward to the great bend of the Volga. The intermediate area was studded with large lakes and morasses. Thus an almost complete water barrier of shallow sea located just west of the low Ural Mountains, separated Europe from Asia during the Würm glaciation and the following period of glacial retreat. The broken connection was restored just before the dawn of history by a slight elevation of the land and the shrinking of the Caspian-Aral Sea through the increasing desiccation which has left its present surface below sea level. An important element in the maintenance of the isolation of this Nordic cradle on the south is the fact that from earliest times down to this day the pressure of population has been unchangeably from the bleak and sterile north, southward and eastward, into the sunny but enervating lands of France, Italy, Greece, Persia and India. In these forests and steppes of the north, the Nordic race gradually evolved in isolation and at an early date spread north over the Scandinavian Peninsula together with much of the land now submerged under the Baltic and North Seas. Nordic strains form everywhere a substratum of population throughout Russia and underlie the round skulled Slavs who first appear a little over a thousand years ago as coming not from the direction of Asia but from south Poland. Burial mounds called kurgans are widely scattered throughout Russia from the Carpathians to the Urals and contain numerous remains of a dolichocephalic race,—in fact, more than three-fourths of the skulls are of this type. Round skulls first become numerous in ancient Russian graveyards about 900 A. D. and soon increase to such an extent that in the Slavic period from the ninth to the thirteenth centuries one-half of the skulls were brachycephalic, while in modern cemeteries the proportion of round skulls is still greater. The ancient Nordic element, however, still forms a very considerable portion of the population of northern Russia and contributes the blondness and the red-headedness so characteristic of the Russian of to-day. As we leave the Baltic coasts the Nordic characters fade out both toward the south and east. The blond element in the nobility of Russia is of later Scandinavian and Teutonic origin.