How does novelty arise?

 

 

Natural selection is a force for both change and conservation (see Lecture 4). Indeed, selection often acts to keep things the "same." For example, finches on the Galapagos islands are under intense selection pressure, but show little long term evolutionary change.

 

How then, do we get novelty? One source is changes in developmental timing. This might explain some features of human evolution, such as the shape of our skull (see Campbell p. 459, fig. 24.14)

 

Another source might be gene (and genome) duplications.

  • One copy of a gene, natural selection acts to conserve function Ébut, if the gene duplicates
  • Two copies, one retains original function, other may become non-function (pseudogene) or may evolve a new function

Gene duplication may have played a major role in the evolution of vertebrates (see Campbell p. 460, fig. 24.16)