Genome change and evolutionary change

Abstract

The word ‘evolution’, which literally means unfolding, describes the changes of form which have taken place in living organisms over time. As such, it necessarily involves internal and external morphological modifications, resulting in the production of new forms of life from pre-existing forms. The essential problem in evolution, therefore, is to account for such changes. Any permanent change in morphology must, of necessity, involve a change in development, so that evolution can only be satisfactorily defined in terms of the changes in the developmental programmes that have ultimately been responsible for producing different morphologies. In relation to such changes we can ask six critical questions:

• Q. 1 How is morphological novelty generated? Is it simply that the same genes, or else divergent duplicates of them, have been assembled into different developmental circuits, or has there been a genuine evolution of new genes with new functions?

• Q.2 What do changes at the molecular level tell us about morphological change?

• Q.3 Do chromosome changes play any role in producing morphological change?

• Q.4 Do evolutionary changes depend on large-scale genomic reorganization?

• Q.5 Is speciation in any way involved with the inception of major morphological change?

‘The past consists of not what actually happened but what men believe happened.’ Gerald White Jackson