64 THE HYPOTHESIS OF THE OASIS-WORLD. 
much progress in breaking up the continuity of the loess steppes, and to widen 
the distance between habitable areas within the region thus isolated. The reac- 
tion did not begin until the inflow of water became insufficient to maintain the 
inland sea at its maximum of expansion. After this would come the change to 
segregation of communities, first into larger groups of loosely connected units, 
then the breaking up of.these into smaller groups. Within the wider limits of 
the region more or less intercourse could exist between the delta-oases on some 
stretches along the piedmont belt, and often still more easily between those on 
opposite sides of relatively low mountain ranges. The essential condition was 
a sufficient frequency of springs or streams to permit travel on foot. 
Under such conditions, continued through thousands of years, the related 
peoples, beconiing isolated in oases or oasis groups, or in high mountain valleys, 
would differentiate, each evolving its own culture along lines influenced by 
inherited traditions, environment, and racial character. The development would, 
in general, on account of isolation, be peaceful, and, while alone and uninterrupted, 
would lack the benefit of acquisition of the new factors that come with inter- 
course with unrelated peoples. The growth of population on these restricted 
areas was necessarily accompanied by evolution in social organization. We find 
the people living in towns, where the long continuance of life under individual 
town government, practically without external relations, while developing indi- 
viduality, must have given the many separate peoples thus situated certain fun- 
damental political characteristics common to all. In the same way, in so far as 
the physical environment was similar, certain classes of customs, arts, and occu- 
pations must have evolved along similar lines. In so far as the peoples of larger 
or minor groups of oases differentiated from the same stock or from the same 
language stock, their languages would retain traces of the original generalized 
speech. All these are ethnographic data to be carefully searched for in sifting 
and analyzing the results of future investigations. 
But several data among our finds from this earliest Anau culture show 
that more or less intercourse existed with other parts of the oasis-world. Tur- 
quoise beads, used as burial gifts with the skeleton of a child, must have come 
from Persia, where turquoise is known both to the south of Anau and farther 
eastward on the plateau; the same inference is to be drawn from the presence of 
copper. 
We have at present no means of knowing how the earliest culture of the 
settlements at Anau stands in relation to the generalized cultures of Central Asia 
before the segregation into isolated communities, for there have been made no 
other systematic excavations anywhere to discover traces of the older civilizations, 
excepting in Susiana, southwest of the Iranian plateau, to which I shall refer 
farther on. The constituents of the earliest culture found at Anau presuppose 
a previous evolution during many thousand years. How slow it must have been 
is shown by the almost unvarying character of the pottery during the two mil- 
lenniums at the North Kurgan. 
When we compare this culture with that which succeeded it (No. II) on the 
same kurgan, we find both differences and points in common. Each has its own 
peculiar technique in pottery and scheme of ornamentation in painted decoration. 
The mace and artificially formed slingstones appear. But both cultures had in 
