SOUTHERN ARABIA—COON 389 
present. The Empty Quarter, after all, is nothing but an eastward 
extension of the Sahara, a part of the general belt of arid uplands 
extending across vast expanses of Africa and Asia. Since the climatic 
history of the Sahara is now partly known, it is possible to reason by 
analogy with some hope of justification. 
During the Pleistocene, a number of pluvial periods turned the 
Sahara, at alternate intervals, into a great plain of grass and park- 
lands, drained by huge rivers which carved its deep wadies, now water- 
less and denuded, into sculptural masterpieces of erosion. In south- 
ern Arabia, the size and volume of the dry river courses bear evidence 
that the same process took place here as well, and that during these 
periods of abundant rainfall the Empty Quarter itself formed a 
grassy plain of lesser size, offering food and shelter to herds of rumi- 
nant mammals, and to man. 
After the last pluvial maximum, Arabia, like the Sahara, began to 
dry out. The abandonment of Marib, the gradual disuse of the ter- 
races along the Yemen escarpment, and the turning of the northern 
Arabs to pastoral nomadism with dependence on the camel, may all 
have been secondary manifestations of this increasing desiccation, 
and we have no evidence that the drying-out process has yet come to 
an end. Arabia today holds somewhat less than 6 million people. 
Five thousand years ago, when agriculture was already old but lit- 
erate civilization new, Arabia might presumably have held twice that 
number. If we are to reconstruct the history of Arabia, however, we 
must turn back still farther, and postulate a time in which the whole 
southern border of the peninsula resembled the present Dhofar, and 
in which the Empty Quarter and the regions north of it were grassy 
plains. 
At that time, it is possible that Arabia was a home of human beings 
of ancestral European type, and advanced beyond their fellows in the 
glacial north. It is too early, however, to present this hypothesis with 
conviction, for at present Paleolithic archeology in Arabia may be 
said hardly to have begun. In the Nejd, Doughty * found Paleolithic 
implements, in the form of hand axes; Henry Field,‘ in a motor trip 
across Transjordania and the desert border of Iraq, established the 
presence of Paleolithic industries from the Acheulean stage upward, 
while Philby,* in his recent trip along the southern border of the 
Empty Quarter, has likewise discovered Paleolithic implements of 
nature as yet unstated. 
Miss Caton-Thompson,* however, has found paleoliths in situ in 
the Hadhramaut; these are of Levalloisian type, and poorly executed. 
® Doughty, 1923. 
‘Field, 1934. 
5Philby, 1937. 
*Caton-Thompson and Gardner, 1939. 
