GRASSLAND AND FARMLAND—SMITH 363 
and finally the teachers of the human race. From this base many cul- 
ture elements have spread to all parts of the world. It is fortunate 
for those of this generation that the Mesopotamians wrote on endur- 
ing tablets of clay. 
Then, as now, men who traveled carried with them ideas, techniques, 
and various culture elements. A trail of fragments of painted pottery 
leads from Shushan, near the eastern edge of Mesopotamia, and marks 
the road by which culture elements went from Mesopotamia to China. 
Through this dry land a natural road proceeds from oasis to oasis. 
Where mountain streams reach the plains at the foot of the mountains 
Equator DISTRIBUTION 
—OF the 
TRACTION PLOW 
—BEFORE THE - 
AGE OF DISCOVERY 
aoric OF CANCE 
a ag a ~ 
LA, 
Ly, 
Zp 
Ficure 4.—Distribution of the traction plow before the age of discovery. (After 
Carl Bishop.) The plow had wider spread than wheat. It was drawn by ox, 
buffalo, and donkey, and occasionally by the elephant. 
natural refreshment stations exist. No one knows how long these 
little Niles have been feeding humanity. These fertile spots en- 
courage travel across Iran, western Turkestan, and eastern Turkestan. 
Thence the trail continues eastward across Mongolia and down the 
Wei River valley, past the present city of Sian and on to the great 
bend of the Hwangho at the southwest corner of the province of 
Shansi. 
No one knows when culture elements first began to pass northeast- 
ward from Mesopotamia over these stepping stones of fertility. This 
seems to make logical the Chinese claim that Chinese civilization had 
its origin in the Sian Valley near the great bend of the Hwangho. 
