THE UNITY OF ECOLOGY — DARLING 469 



ment not as uniform as our school geography books would lead us to 

 believe. Cattle are much more efficient converters, as individuals, of 

 forage into meat, milk, and leather, and they can be used for traction 

 and as weight carriers ; but their heavy water requirements govern the 

 possible nomadic routes. The camel, on the other hand, gives the 

 nomad the greatest penetration or retreat into arid regions. Lastly, 

 the horse was of great benefit as a producer of meat, milk, and tractive 

 power. Domestication of these animals meant their presence where 

 and when they were wanted, their mental and even physical charac- 

 teristics so far modified that they did not move as quickly as wild ones. 

 In consequence, the animals were in general on the ground for a 

 longer period and in greater numbers than when they were wild. The 

 nomad society arising gradually from the more sedentary agricultural 

 group would early realize that overgrazing hung like a sword of 

 Damocles. The price of the life-way of grazing animals is move- 

 ment, the brand of Ishmael. In the ideal, agriculture is concentra- 

 tion of effort, or intensification: pastoralism is conscious, well-or- 

 ganized diffusion. 



Yet man does not prefer constant or random movement. Even 

 the most highly developed nomads do not go far, no more than 150 

 or possibly 200 miles of farthest distance in the year, and relatively 

 long spells of pitched tents are desired. The women wish it so, caring 

 nothing for floristic composition of the grazing. At best the nomad 

 was on the chernozem soils of the Ukraine or in delectable valleys : at 

 worst in the wastes of the Gobi or the Tarim Depression. Nomadism 

 in its highest development did not occur until after 1500 B.C. and it 

 came with achievement of that maximum state of mobility, the mas- 

 tery of riding horses, as distinct from using this animal for traction. 



Horse riding seems to have arisen on the plateau of northwest 

 Persia. If you have ever ridden a pony of stocky Prjewalski type you 

 will know the relief of getting off it for a rest: but once you have 

 ridden one of the delicately controllable, long-gaited creatures of 

 what we now call the Arab type, one's whole outlook changes on the 

 mounted state. Man well mounted is a superior being, and the nomad 

 soon geared his way of life to that which gave the male element swift 

 and far range ; even his eyes are a yard higher above the ground — no 

 mean advantage. We cannot know the details of the dominant muta- 

 tion which produced the dish-faced, long-necked, sloping-shouldered, 

 fine-boned "horse of heaven," as it came to be called, but nomadic man 

 quickly made use of it. Even his status changed, producing the cheva- 

 lier, the caballero, and the knight, who were with us till the Land 

 Rover came and the girls took over the pony clubs. 



Now came maximum exploitation of the steppe environment, not 

 only nomadism which, as I have said, is never over a very long dis- 

 tance, but in migration. The Indo-European tribes began their great 



