The first step is to have a clear idea of what actually exists at the present moment. There are an almost endless number of minor varieties of the human race, but none of them of sufficient importance to imply diversity of origin, with the exception of four, or at the most five or six fundamental types, which stand so widely apart that it is difficult to imagine that they are all descended from a common pair of ancestors. These are the white, yellow, and black races of the Old World, the copper-coloured of America, and perhaps the olive-coloured of Malaysia and Polynesia, and the pygmy races of Africa and Eastern Asia. The difficulty of supposing these races to have all sprung from a single pair will at once be apparent if we personify this pair under the name of Adam for the first man and Eve for the first woman, and ask ourselves the question, what do we suppose to have been their colour? But colour alone, though the most obvious, is by no means the sole criterion of difference of race. The evidence is cumulative, and other equally marked and persistent characters, both of physical structure and of physiological and mental peculiarities, stand out as distinctly as differences of colour in the great typical races. For instance, the hair is a very persistent index of race. When the section of it is circular, the hair is straight and lank; when flattened, woolly; and when oval, curly or wavy. Now these characters are so persistent that many of the best anthropologists have taken hair as the surest test of race. Everywhere the lank and straight hair and circular section go with the yellow and copper-coloured races; the woolly hair and flat section with the black; and the wavy hair and oval section with the white races. The solid framework of the skeleton also affords very distinctive types of race, especially where it is looked at in a general way as applicable to great masses of pure races, and not to individuals of mixed race, like most Europeans. The skull is most important, for it affords the measure of the size and shape of the brain, which is the highest organ, and that on which the differentiation of man from the lower animals mainly depends. The size of the brain alone does not always afford a conclusive proof of mental superiority, for it varies with sex, height, and other individual characters, and often seems to depend more on quality than on quantity. Still, if we take general averages, we find that superior and civilized races have larger brains than inferior and savage ones. Thus the average brain of the European is about 1500 cubic centimètres, while that of the Australian and Bushman does not exceed 1200.