Invasions of new races have ordinarily arrived in successive waves, the earlier ones being quickly absorbed by the conquered, while the later arrivals usually maintain longer the purity of their type. Consequently the more recent elements are found in a less mixed state than the older and the more primitive strata of the population always contain physical traits derived from still more ancient predecessors. Man has inhabited Europe in some form or other for hundreds of thousands of years and during all this lapse of time the population has been as dense as the food supply permitted. Tribes in the hunting stage are necessarily of small size, no matter how abundant the game and in the Paleolithic period man probably existed only in specially favorable localities and in relatively small communities. In the Neolithic and Bronze periods domesticated animals and the knowledge of agriculture, although of primitive character, afforded an enlarged food supply and the population in consequence greatly increased. The lake dwellers of the Neolithic were, for example, relatively numerous. With the clearing of the forests and the draining of the swamps during the Middle Ages and, above all, with the industrial expansion of the last century the population multiplied with great rapidity. We can, of course, form little or no estimate of the numbers of the Paleolithic population of Europe and not much more of those of Neolithic times, but even the latter must have been very small in comparison with the census of to-day. Some conception of the growth of population in recent times may be based on the increase in England. It has been computed that Saxon England at the time of the Conquest contained about 1,500,000 inhabitants, at the time of Queen Elizabeth the population was about 4,000,000, while in 1911 the census gave for the same area some 35,000,000. The immense range of the subject of race in connection with history from its nebulous dawn and the limitations of space, require that generalizations must often be stated without mention of exceptions. These sweeping statements may even appear to be too bold, but they rest, to the best of the writer’s belief, upon solid foundations of facts or else are legitimate conclusions from evidence now in hand. In a science as recent as modern anthropology, new facts are constantly revealed and require the modification of existing hypotheses. The more the subject is studied, the more provisional even the best-sustained theory appears, but modern research opens a vista of vast interest and significance to man, now that we have discarded the shackles of former false viewpoints and are able to discern, even though dimly, the solution of many of the problems of race. In the future new data will inevitably expand and perhaps change our ideas, but such facts as are now in hand and the conclusions based thereupon are provisionally set forth in the following chapters and necessarily often in a dogmatic form.