Gradualism, Contingency, and Punctuated Equilibria

Since Ed is in Vegas again, I offered to put up some guest posts to help alleviate the terrible burden being placed on him.  And today being Darwin Day, I thought I’d put up a post on evolution.

As a consequence of lacking data supporting their own explanations, creationists, like other denialists, have to rely on attacking perceived weaknesses in the mainstream theories.  A popular target arises whenever disagreements between scientists over aspects of the theory crop up.  These disagreements are then exaggerated so as to makeit seem as if the whole edifice is crumbling, when in reality it is just a minor difference in opinions, both of which can be explained by the theory.

In evolution, one such disagreement is between gradualism and punctuated equilibria.  Broadly speaking, gradualism is the idea that changes accumulate over time, while punctuated equilibria is the idea that there are short periods of lots of change interspersed among long periods of little change.  Since these two ideas appear to be contradictory, creationists love to use the debate over the two concepts as evidence that evolution is wrong.  However, the two concepts are not only not contradictory, under the right circumstances gradualism results in punctuated equilibria.

Read the rest of this entry »