On the eschatology of the human condition  (Page 6/7)

Time-lags

There is yet another factor which must be recognized in our description of the future population. We know that the modification of social attitudes or the realization of any great enterprise requires a certain lead time; between the decision and the effect there often intervene many years. Such time lags also occur in natural phenomena and have the utmost significance for the questions that concern us here. We may decide today to ban the use of pesticides, but the maximum value of pesticide contamination of, let us say, fish, will nevertheless not be realized for many years; we may decide, or be constrained, to stabilize population now, but population will nevertheless continue to increase for some time into the future due: to actions and decisions taken earlier but whose consequence have not yet unfolded. Even so apparently simple a matter as the national reduction of speed limits requires a not incon­siderable time interval between the impulse of necessity and reaction of implementation. So too it is amongst microcosmic societies. The natural "velocity" of population growth may carry population to magnitudes greater than those sustainable in equilibrium conditions (just as a ball thrown upward against the restraining force of gravity continues to rise for some time despite the downward tug), thereby setting the stage for subsequent decline which itself may carry population below sustainable levels. Thus we come to anticipate the possibility and indeed the probability of cyclical oscillations in the population life cycle curve, oscillations superimposed upon the general long term decline which itself follows the initial surge of exponential growth and logistic constraint. The early portions of such a curve are shown in [link] , which illustrates the life cycle of a population of Paramecia grown in a limited environment. During the first three days, the initially small Paramecia population increases exponentially; at the end of that time, the constraints of their limited environment become significant and the rate of increase of population declines to zero, while the population itself attains its maximum value at the end of 6 days. Thereafter, -it declines, at first rapidly, and then, as its density decreases, more slowly, until a local minimum value is attained at about 16 days, after which another period of increase is observed, which slows to another but this time lesser maximum, and is followed by a decline initiating a new cycle.

The period from 6 to 8 days constitutes an era of catastrophe for the Paramecia: population collapses to about 60 percent of its maximum value within a relatively brief interval. We can imagine governments crumbling, learning and art extinguished, a mean, brief and ugly life the reward for those who survive. By contrast, the long stable interval from 8 to 17 days which follows must appear most agreeable by contrast. One can hardly avoid drawing the parallel with the Fall of Rome and the subsequent stable medieval period.