The World peopled by Migration from one Centre by Pleistocene Man--The Primary Groups evolved each in its special Habitat-- Pleistocene Man: _Pithecanthropus erectus_; The Mauer jaw, _Homo Heidelbergensis_; The Piltdown skull, _Eoanthropus Dawsoni_--General View of Pleistocene Man--The first Migrations--Early Man and his Works--Classification of Human Types: _H. primigenius_, Neandertal or Mousterian Man; _H. recens_, Galley Hill or Aurignacian Man-- Physical Types--Human Culture: Reutelian, Mafflian, Mesvinian, Strepyan, Chellean, Acheulean, Mousterian, Aurignacian, Solutrian, Magdalenian, Azilian--Chronology--The early History of Man a Geological Problem--The Human Varieties the Outcome of their several Environments--Correspondence of Geographical with Racial and Cultural Zones. In order to a clear understanding of the many difficult questions connected with the natural history of the human family, two cardinal points have to be steadily borne in mind--the specific unity of all existing varieties, and the dispersal of their generalised precursors over the whole world in pleistocene times. As both points have elsewhere been dealt with by me somewhat fully[1], it will here suffice to show their direct bearing on the general evolution of the human species from that remote epoch to the present day. It must be obvious that, if man is specifically one, though not necessarily sprung of a single pair, he must have had, in homely language, a single cradle-land, from which the peopling of the earth was brought about by migration, not by independent developments from different species in so many independent geographical areas. It follows further, and this point is all-important, that, since the world was peopled by pleistocene man, it was peopled by a generalised proto-human form, prior to all later racial differences. The existing groups, according to this hypothesis, have developed in different areas independently and divergently by continuous adaptation to their several environments. If they still constitute mere varieties, and not distinct species, the reason is because all come of like pleistocene ancestry, while the divergences have been confined to relatively narrow limits, that is, not wide enough to be regarded zoologically as specific differences.