374 POPULAR SCIENCE MONTHLY. 



the Himalayan line. In these early days, moreover, the penisula por- 

 tion of the Old World constituted a practically continuous land-mass. 

 Toward the west India was connected with Africa, and Africa was 

 joined to Europe by two or more isthmuses. In the opposite direction, 

 the Malaysian peninsula was extended toward Australia through what 

 are now the separate islands of Sumatra, Borneo and Java; Australia 

 was likewise connected with New Guinea, and the immense island con- 

 tinent thus constituted was to all intents and purposes coterminous 

 with the southeasterly extensions of Malaysia. It must have been pos- 

 sible, therefore, at this time for primeval man to proceed from the 

 Indo-Malaysian abode along the central latitudes, to the Atlantic on 

 the west, and far out across the Pacific on the east, without having to 

 cross the open seas. 



During the course of the pleistocene period the ice disappeared from 

 the north and glaciation set in from the south, the glaciers in this in- 

 stance proceeding from the antarctic regions and from the highlands of 

 the southern peninsulas. The thermal equator also moved north of the 

 geographical equator at this time, and during the long interglacial epoch 

 that followed, lasting at least ten thousand years, the whole Northern 

 Hemisphere enjoyed an equable climate, ranging from tropical to tem- 

 perate conditions and devoid of great seasonal variations. The effect of 

 this change must have been to limit the lines of migration toward the 

 far south, and greatly to extend the course of dispersion towards the 

 northeast and northwest. Or to put it more exactly : entry into South 

 Africa was probably barred by the increasing cold, but as the influence 

 of the southern glaciers did not extend as far north as the Indo-Medi- 

 terranean-Malaysian belt, the inhabitants of this region were doubtless 

 free to wander east and west as before along the central latitudes. Nor 

 did climatic conditions any longer prevent men from penetrating into 

 the continental area beyond. Mountain masses still barred the way 

 in the center, to be sure ; but passages were open on either side ; from 

 the Mediterranean region into Europe, and from the Malaysian region 

 into Asia. Above the Himalayan line the Tibetan plateau interposed 

 itself between these Mediterranean and Malaysian emigrants and prob- 

 ably kept them for long ages apart. For this reason, and doubtless also 

 because the maritime regions offered greater attractions to primeval 

 man than the inland areas, the earliest lines of migration appear to 

 have followed the Atlantic and Pacific coasts of the Eastern Hemi- 

 sphere into the northern latitudes, where the shore lines of the 

 Eurasian continent stretch out toward America. During the first and 

 second interglacial epochs the two hemispheres were, indeed, practically 

 coterminous in these parts. This was due to the fact that the level of the 

 northern oceans was lowered at these times, leaving land-bridges exposed 

 to view which have since become covered by the sea. As a result, the 



