938 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1949 
Marett held that people having food deficient in some essential ele- 
ment, say calcium, phosphorus, or iodine, gradually develop the ability 
to conserve this element. That is, in the evolutionary process the 
ability to get along satisfactorily with only a little of some element 
would have survival value. Such people would be most likely to have 
children able to thrive and grow strong. But in the process, size, 
skin color, and other features, even the psychological characteristics 
and social traits, are altered. Marett believed that differences in food 
composition, most of which were closely related to the local environ- 
ment before the modern period, had a great deal to do with the origin 
of races, with the physical and social differences among the different 
peoples of the earth. 
Marett argued, for example, that in regions with acid soils deficient 
in calcium, people of small size would be favored. The physiological 
strain of lactation upon females would be much greater in humid 
regions where soils are generally leached and acid and the foods de- 
ficient in calcium and phosphorus, than in arid regions where soils 
usually contain abundant lime (calcium). Thus on acid soils where 
food is deficient in calcium the bodily strain would lead to adjustments 
for economizing lime through decreased size, especially of bones. He 
suggested that the operation of these forces may have been important 
in the development of fine bones among modern people as contrasted 
to our more coarse-boned ancestors. Such changes are very gradual, 
and are not marked until after long-living in a particular landscape. 
MAN AS A CULTIVATOR 
As civilization developed, man became a cultivator. He began to 
direct the course of nature toward his own ends, and ceased to be 
simply a food gatherer dependent only upon the natural bounty of 
the landscape. He ceased to be primarily a thief, and became a 
grower, 2 homemaker, a planner, and a conservationist in the only 
sense the term has any social meaning. As he gained in experience 
he learned to satisfy himself more easily; in fact, some people in the 
society could cease to be food gatherers. Social structures rose with 
the evolution of trades and professions. As the efficiency of food 
production increased, more and more people could be released from 
food gathering to develop the arts and sciences, to make the other 
things man needed for his health and comfort, and, unfortunately, 
to make war. 
From the dawn of history to the rise of modern science the accumu- 
lation of learning about agriculture was a terribly slow process. 
Experience, which was passed down from father to son over the genera- 
tions, was the only guide. Only a few departures were made, because 
there was no substitute for such experience. Further, there was little 
