THE ECOLOGY OF MAN—SEARS 391 
In support we hear further of the sparsely settled Tropics, the vast 
reaches of the sea, the present (United States) agricultural surplus, 
the continuing progress of synthetic chemistry, and the possibilities 
of energy from sun and atom. The extreme advocates have even been 
known to say without a smile that overpopulation is not a menace 
because we’ll soon have space travel. Anyone who has traveled 
bumper to bumper trying to get out of a great metropolis on a holiday 
or to get an inexpensive reservation on a transatlantic steamer on 
short notice might reserve judgment on this latter point, especially 
if he recalled that perhaps 120,000 people are added daily to the 
world’s population. Incidentally, to provide adequate food, fiber, 
and living space for these new guests would require the equivalent 
of one Ohio county—some 400 square miles—added to the productive 
land of our planet each 24 hours. This, of course, is not happening 
and in consequence many, perhaps most, of those born in ancient and 
overcrowded lands are doomed to lifetimes of want and privation. 
In the past these lifetimes have been, on the average, brief, owing to 
high infant mortality and the incidence of disease. 
Recently, however, the effects of modern medicine and public health 
measures have been extended over the earth. More people are now 
living for a longer time. To some extent the production of food 
in overcrowded nations has been improved, but this contributes to 
greater numbers surviving rather than a better dietary for all. 
Meanwhile there has been little adjustment, outside of Europe, in the 
birth rate. So we see doubling of the population of Ceylon—an 
inelastic island—in less than a score of years, and agonizing pressures 
in another island, Puerto Rico. In our own country the net rate of 
increase is actually higher than in the overpopulated Orient owing 
to better sanitation, more food, more space, and other advantages 
that protect us for the present. I suspect that we now have the best 
chance we shall have to avoid the fate of older nations, for we still 
have a freedom of choice and action that they have lost. 
A convenient way to show the process in which modern man, no less 
than his ancestors, is involved is by means of the following memoran- 
dum. Using R for resources from the environment, P for population 
in numbers of individuals in a given group, and C for the culture 
of that group, we first write a fraction 
R 
Pp 
This means plainly enough that the per capita share of resources, or 
any of them (space, water, minerals, timber, etc.) , increases with their 
abundance and decreases with rising population. But if we compare, 
say, Brazil rich in resources and Denmark with few, we see that our 
4925205926 
