The chief sources of flint are the chalk deposits of Cretaceous age that occur so plentifully in western Europe, as seen, for example, in the white cliffs along the southern coast of England. Approaching one of these cliffs, you will find it studded with parallel beds of flint nodules. Wherever flint occurs stone-age relics are apt to be abundant. The chalk of England, Belgium and northern France is the same age as the flint-bearing calcareous deposits of Spain and southern France; but the latter have not the white chalky appearance and are much harder;
hence are full of caverns and rock shelters about which we shall speak later.
One great difficulty that confronts the student of human origins is the paucity and fragmentary character of the evidence. This evidence is limited to two kinds: skeletal and cultural remains. The first of these is the rarest and at the same time the most incontrovertible. Not one complete skeleton has as yet been found. The less durable parts are missing. The cranial cap, the lower jaw, a few teeth, bones of the extremities, are the somatologist's chief sources of information. Except in rare instances, the face bones and the base of the skull are missing.
