In other words those groups of mankind which at an early period found refuge in the Americas, in Australia, in Ethiopia, or in the islands of the sea, represent to a large extent stages in man's physical and cultural development, from which the more energized inhabitants of Eurasia have long since emerged. In some cases, as in Mexico and Peru, the outlying races developed in their isolation a limited culture of their own, but, for the most part, they have exhibited, and continue to this day to exhibit, a lack of capacity for sustained evolution from within as well as a lack of capacity to adjust themselves of their own initiative to the rapid changes which modern times impose upon them from without. In Eurasia itself this same inequality of potential capacity is found, but in a lesser degree, and consequently, in the progress of humanity, there has been constant friction between those who push forward and those who are unable to keep pace with changing conditions. Owing to these causes the history of mankind has been that of a series of impulses from the Eurasiatic continent upon the outlying regions of the globe, but there has been an almost complete lack of reaction, either racial or cultural, from them upon the masses of mankind in Eurasia itself. There have been endless conflicts between the different sections of Eurasia, but neither Amerinds, nor Austroloids, nor Negroes, have ever made a concerted attack upon the great continent. * * * * * Without attempting a scientific classification of the inhabitants of Eurasia, it is sufficient to describe the three main races. The first are the yellow-skinned, straight black-haired, black-eyed, round-skulled Mongols and Mongoloids massed in central and eastern Asia north of the Himalayan system. To the west of them, and merged with them, lie the Alpines, also characterized by dark, but not straight, hair, dark eyes, relatively short stature, and round skulls. These Alpines are thrust like a wedge into Europe between the Nordics and the Mediterraneans, with a tip that reaches the Atlantic Ocean. Those of western Europe are derived from one or more very ancient waves of round-skulled invaders from the East, who probably came by way of Asia Minor and the Balkans, but they have been so long in their present homes that they retain little except their brachycephalic skull-shape to connect them with the Asiatic Mongols. South of the Himalayas and westward in a narrow belt to the Atlantic, and on both sides of the Inland Sea, lies the Mediterranean race, more or less swarthy-skinned, black-haired, dark-eyed, and long-skulled. On the northwest, grouped around the Baltic and North Seas, lies the great Nordic race. It is characterized by a fair white skin, wavy hair with a range of color from dark brown to flaxen, light eyes, tall stature, and long skulls.