On the Generation and Growth of a Population

1. Some of the factors which complicate the theoretical and practical quantitative study of human populations may be negligible in the treatment of certain lower biological populations. The comparatively short lifetime and the regularity of breeding epochs is one simplification, which, incidentally suggests the interval between breeding epochs as a natural unit of age. It may also be that fertility and mortality rates at ages are more nearly constant in time in any case, time fluctuations in these rates due to environment changes are more amenable to experimental control in colonies of lower animals or plants than in human popu lations.