The Two Imperatives

Abstract

The two basic evolutionary needs of all species of higher animal are survival to reproductive age, and death when survival offers no reproductive advantages to the species. The thesis of this essay is that both requirements are solved genetically by methods which involve control of mutability in the broad sense. For survival there must be an adequate appearance of mutants to ensure possibilities of adjusting to changes in the ecosystem or occupying any new ecological niches which may become available. It is, however, just as important biologically that the old generation should be discarded as soon as the new one is established. The mechanism is that of senescence, by which, once reproductive performance is completed, ageing develops almost certainly by the progressive acceleration of somatic mutation. Either by way of increasing vulnerability to environmental impacts or by intrinsically developed disease (cancer, etc.), death eventually ensues.