Population cycle

Olaus Magnus, the Archbishop of Uppsala in central Sweden, identified that species of northern rodents had periodic peaks in population and published two reports on the subject in the middle of the 16th century.

When their population outgrows the resources of their habitat, lemmings migrate, although contrary to popular myth, they do not jump into the sea.

There are other species which have irregular population explosions such as grasshoppers where overpopulation results in locust swarms in Africa and Australia.

Societies as diverse as those of England and France during the Roman, medieval, and early modern eras, of Egypt during Greco-Roman and Ottoman rule, and of various dynasties in China all showed similar patterns of political instability and violence becoming considerably more common after times of relative peace, prosperity, and sustained population growth.

Quantitatively, periods of unrest included many times more events of instability per decade and occurred when the population was declining, rather than increasing.