CHAPTER IV: ORIGINAL INTERNAL FACTORS.

§ 22. As with the original external factors, so with the original internal factors—an adequate account of them supposes a far greater knowledge of the past than we can get. On the one hand, from men’s bones, and objects betraying men’s actions, found in recent strata and in cave-deposits, dating back to periods since which there have been great changes of climate and re-distributions of land and sea, we must infer that the habitats of tribes have been ever undergoing modifications; though what modifications we can but vaguely guess. On the other hand, alterations of habitats imply in the races subject to them adaptive changes of function and structure; respecting most of which we can know little more than their occurrence.

Such fragmentary evidence as we have does not warrant definite conclusions respecting the ways and degrees in which men of the remote past differed from men now existing. There are, indeed, remains which, taken alone, indicate inferiority of type in ancestral races. The Neanderthal-skull and others like it, with their enormous supra-orbital ridges so simian in character, are among these. There is also the skull lately found by Mr. Gillman, in a mound on the Detroit river, Michigan, and described by him as chimpanzee-like in the largeness of the areas over which the temporal muscles were inserted. But as this remarkable skull was found along with others that were not remarkable, and Edition: current; Page: [39] as such skulls as that from the cave in the Neanderthal are not proved to be of more ancient date than skulls which deviate little from common forms, no decisive inferences can be drawn. A kindred, but perhaps a more positive, statement, may be made respecting that compression of the tibiæ in certain ancient races, which is expressed by the epithet “platycnemic.” First pointed out by Prof. Busk and Dr. Falconer, as characterizing the men who left their bones in the caves of Gibraltar, this peculiarity, shortly afterwards discovered by M. Broca in the remains of cavemen in France, was observed afresh by Mr. Busk in remains from caves in Denbighshire; and more recently Mr. Gillman has shown that it is a trait of tibiæ found along with the rudest stone-implements in mounds on the St. Claire river, Michigan. As this trait is not known to distinguish any races now living, while it existed in races which lived in localities so far apart as Gibraltar, France, Wales, and North America, we must infer that an ancient race, distributed over a wide area, was in so far unlike races which have survived.

Two general conclusions only seem warranted by the facts at present known. The first is that in remote epochs there were, as there are now, varieties of men distinguished by differences of osseous structure considerable in degree, and probably by other differences; and the second is, that some traits of brutality and inferiority exhibited in certain of these ancient varieties, have either disappeared or now occur only as unusual variations.

§ 23. So that about the original internal factors, taken in that comprehensive sense which includes the traits of prehistoric man, we can ascertain little that helps us. Still we may fairly draw from the researches of geologists and archæologists the important general inferences that throughout long-past periods, as since the commencement of history, there has been going on a continuous differentiation Edition: current; Page: [40] of races, a continuous over-running of the less powerful or less adapted by the more powerful or more adapted, a driving of inferior varieties into undesirable habitats, and, occasionally, an extermination of inferior varieties.

And now, carrying with us this dim conception of primitive man and his history, we must be content to give it what definition we may, by studying those existing races of men which, as judged by their visible characters and their implements, approach most nearly to primitive man. Instead of including in one chapter all the classes and sub-classes of traits to be set down, it will be most convenient to group them into three chapters. We will take first the physical, then the emotional, lastly the intellectual.