During recent years much light has been shed on the physiographical conditions of Central Asia in early times. Stein's[570] explorations in 1900-1 and 1906-8 in Chinese Turkestan, the Pumpelly Expeditions[571] in 1903 and 1904 in Russian Turkestan, the travels of Sven Hedin[572] in 1899-1902, and 1906-8, of Carruthers[573] in N.W. Mongolia, and the researches of Ellsworth Huntington[574] (a member of the first Pumpelly Expedition) in 1905-7 all bear testimony to the variation in climate which the districts of Central Asia have undergone since glacial times. There has been a general trend towards arid conditions, alternating with periods of greater humidity, when tracts, now deserted, were capable of maintaining a dense population. Abundant evidence of man's occupation has been found in delta oases formed by snow-fed mountain streams, or on the banks of vanished rivers, where now-a-days all is desolation, though, as T. Peisker[575] points out, climate was not the sole or even the main factor in many areas. In some places, as at Merv, the earliest occupation was only a few centuries before the Christian era, but at Anau near Askhabad some 300 miles east of the Caspian, explored by the Pumpelly Expedition, the earliest strata contained remains of Stone Age culture. The North Kurgan or tumulus, rising some 40 or 50 feet above the plain, showed a definite stratification of structures in sun-dried bricks, raised by successive generations of occupants. H. Schmidt, who was in charge of the excavations, was able to collect a valuable series of potsherds, showing a gradual evolution in form, technique and ornamentation, from the earliest to the latest periods. One point of great significance for establishing cultural if not physical relationships in this obscure region is the resemblance between the geometrical designs on pots of the early period and similar pottery found by MM. Gautier and Lampre[576] at Mussian, and by M. J. de Morgan[576] at Susa, while clay figurines from the South Kurgan (copper culture) are clearly of Babylonian type, the influence of which is seen much later in terra-cotta figurines discovered by Stein[577] at Yotkan.