Natural selection and the regulation of density in cyclic and non-cyclic populations

What determines population density? Animal ecologists debated this question in the postwar years with as much fervour as bishops at an Ecumenical Council, and with as little thought of settling their differences experimentally. As one of the heretics, I was in schism with the orthodox doctrine of density dependence to which David Lack adhered (Nicholson, 1933; Smith, 1935; Lack 1954a). One of Lack’s contributions was putting this doctrine into an evolutionary context; it is therefore ironical that certain ideas he disapproved of (Chitty, 1952; Lack 1954b) should, after a long metamorphosis, have led to my outdoing him in attempting to tie together natural selection and the regulation of numbers (Chitty, 1967a; 1970). However gross the errors of this still-untested view, they are at least in a direction Lack approved of.