These quotations come from a recent paper in Paleobiology by Stephen Jay Gould. What is the new theory? Is it indeed likely to replace the currently orthodox ‘neo-Darwinian’ view? Proponents of the new view make a minimum and a maximum claim. The minimum claim is an empirical one concerning the nature of the fossil record. It is that species, once they come into existence, persist with little or no change, often for millions of years (‘stasis’), and that evolutionary change is concentrated into relatively brief periods (‘punctuation’), these punctuational changes occurring at the moment when a single species splits into two. The maximal claim is a deduction from this, together with arguments drawn from the study of development: it is that evolutionary change, when it does occur, is not caused by natural selection operating on the genetic differences between members of populations, as Darwin argued and as most contemporary evolutionists would agree, but by some other process. I shall discuss these claims in turn; as will be apparent, it would be possible to accept the first without being driven to accept the second.
KeywordsFossil Record Evolutionary Change Nerve Cord Rift Valley Ventral Nerve Cord
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