Hi everyone! Our guest blogger this week, Rick, has kindly shared this thoughtful article below, discussing his take on 2 competing theories of evolution. Do also check out his excellent trilobite collection at http://thedepotenclave.wordpress.com/
Mass Rapid Transit in the Evolutionary Perspective
In the arena of scientific discourse, it is common to encounter opposing schools of thought. The fiercest of evolutionary debates are still seen in the camps from those who buy the theory of ‘Punctuated Equilibrium’ vs. ‘Phyletic Gradualism’.
The former proposes that most species are stuck in a state of stasis whereby there is hardly any net evolutionary change for most of their geological history. If anything is to happen at all, it is largely due to rare and geologically rapid events of speciation, called ‘cladogenesis’. Cladogenesis in effect is like a species becoming two distinct species, rather than through a process of gradual transformation. This theory was first proposed by paleontologists Prof Niles Elderedge and Prof Stephen Jay Gould, because they observed enough discrepancy against classic Phyletic Gradualism in the fossil records – much to the delight of creationists.
Essentially this whole business of Punctuated Equilibrium works like the “Mass Rapid Transit” (pun intended); it is somewhat befitting of the sudden explosion of species, in particular the sudden appearance of the great diversity of life forms – like the complex trilobites with fully specialized eyes – during the epic Cambrian “big bang”. This was a mystery that doesn’t seem to have a fitting prelude.
Now Phyletic Gradualism is a product of classical Darwinism. It maintains that speciation, instead of being immediate, is a slow, uniform, and gradual process. This model is a steady transformation of a whole species into a new one through ‘anagenesis’. This theory at least is consistent with specific taxa like Foraminifera fossils, a group of marine plankton that demonstrated consistent morphological changes from the Paleocene period through to the next 66 million years. Richard Dawkins, not the best atheist but a brilliant evolution theorist, elaborates on more cases of Phyletic Gradualism. This cause will be better fought in the future with more fossil records to mark out the changes not yet exemplified with empirical evidence.
The distinction between Phyletic Gradualism and Punctuate Equilibrium is not always clear and the time scale is of crucial importance. I personally feel that the cases of punctuation in evolution is gradual but compressed, and we need to correctly put it within the context of the grand old evolutionary time scales to get a better picture. This sneaky suspicion is of course extended to the great Cambrian explosion mystery. In conclusion, Gradualism is a better match to rates of change observed in the present, while Punctuated Equilibrium, a better match to rates of change observed through geological history.