Man ranks among the most adaptable organic beings on the earth.  No climate is absolutely intolerable to him.  Only the absence of food supply or of all marketable commodities will exclude him from the most inhospitable region.  His dwellings are found from sea level up to an altitude of 5000 meters or more, where the air pressure is little over one half that on the coast.[1412] Seventeen per cent. of the towns and cities of Bolivia are located at an elevation above 13,000 feet (4000 meters), while Aullagas occupies a site 15,700 feet or nearly 5000 meters above the sea.[1413] Mineral wealth explains these high Bolivian settlements, just as it draws the Mexican sulphur miners to temporary residence in the crater of Popocatepetl at an altitude of 17,787 feet (5420 meters), from their permanent dwellings a thousand meters below.[1414] The laborers employed in the construction of the Oroya railroad in Peru became rapidly accustomed to work in the rarefied air at an elevation of 4000 to 4800 meters.  The trade routes over the Andes and Himalayan ranges often cross passes at similar altitudes; the Karakorum road mounts to 18,548 feet (5,650 meters).  Yet these great elevations do not prevent men going their way and doing the day’s work, although the unacclimated tenderfoot is liable to attacks of mountain sickness in consequence of the rarefied air.[1415]

Man makes himself at home in any zone.  The cold pole of the earth, so far as recorded temperatures show, is the town of Verkhoyansk in northeastern Siberia, whose mean January temperature is 54 F. below zero (-48 Centigrade).  Massawa, one of the hottest spots in the furnace of Africa is the capital of the Italian colony of Eritrea.  However, extremes both of heat and cold reduce the density of population, the scale and efficiency of economic enterprises.  The greatest events of universal history and especially the greatest historical developments belong to the North Temperate Zone.  The decisive voyages of discovery emanated thence, though the needs of trade and the steady winds of low latitudes combined to carry them to the Tropics.  The coldest lands of the earth are either uninhabited, like Spitzenbergen, or sparsely populated, like northern Siberia.  The hottest regions, also, are far from being so densely populated as many temperate countries.[1416] [See maps pages 8, 9, and 612.] The fact that they are for the most part dependencies or former colonial possessions of European powers indicates their retarded economic and political development.  The contrast between the Mongol Tunguse, who lead the life of hunters and herders in Arctic Siberia, and the related Manchus, who conquered and rule the temperate lands of China, shows how climates help differentiate various branches of the same ethnic stock; and this contrast only parallels that between the Eskimo and Aztec offshoots of the American Indians, the Norwegian and Italian divisions of the white race.

[Illustration:  MEAN ANNUAL ISOTHERMS AND HEAT BELTS [Centigrade] 0 deg.C = 32 deg.F. 20 deg.C = 68 deg.F. 30 deg.C = 86 deg.F.]