540 BIOLOGY AND HUMAN LIFE 



from these to the highest. Likewise, the cohesion of individuals, 

 that is, their sticking together, and the division of labor are both 

 rather weak among the lowest races of mankind and become 

 more marked as we go from these to the highest. 



The great drawback of such highly organized cooperative 

 societies lies in the danger that they will grow^ too fast. A hu- 

 mane society saves many people who in a cruder civilization 

 would die of one disease or another— many people who are not 

 very competent and who would in a simpler society be unable 

 to make a living. We do not expose our weaklings and cripples 

 and aged on the rocks or in the desert ; we help them with their 

 burdens and carry them along. This ability to save the weak 

 lowers the death rate among civilized people. This means that 

 as time goes on w^e require that more and more people shall be 

 supported on every acre of usable ground, and that more and 

 more food and other material must be obtained for every day's 

 work. This gives to man's struggle a totally different character 

 from that which we see among other living things. It is no 

 longer a question of swiftness or sharp teeth, of tough hide or 

 long claws, of ability to stand punishment or cruelty in combat. 

 It is more and more a question of skill and intelHgence in uti- 

 lizing both the resources and abilities of our bodies and the 

 resources and conditions of our environment. 



389. Intensive production. The first step in man's conquest 

 of the earth was his learning to produce food by cultivating 

 animals and plants instead of waiting for fisherman's luck— 

 the finding and catching or killing of wild forms. Through 

 steady improvements in the management of the soil and of 

 crops there has been a steady improvement in the yield of man's 

 efforts. To the weapons for defense against wild animals and 

 for the hunt, man had added tools for work (see Fig. 223). 

 The increase of production for labor expended has steadily con- 

 tinued. Sometimes the increase came from improvements in 

 the manner of working, sometimes from improvements in the 

 variety of organism cultivated, sometimes from improvement in 

 the tools. In modern times man has been making systematic 



