“Punctuated Equilibria: an Alternative to Phyletic Gradualism” offers a different perspective to evolution than Darwin’s theory of phyletic gradualism. Phyletic gradualism suggests that new species arise from the slow and steady transformation of entire populations. This implies that the fossil record should consist of a long sequence of continuous intermediate forms linking ancestors and descendants and that morphological breaks in a phyletic sequence is due to imperfections in the fossil record.
Eldredge and Gould proposed a “more adequate” picture to explain evolution especially the rarity of transitional species. Punctuated equilibrium provides an explanation of overall homeostatic equilibria, disturbed rarely, by rapid speciation. Furthermore, aligned with the concept of punctuated equilibria, allopatric speciation is the rapid splitting of lineages from a small sub-population originating in a geographically isolated area from the ancestral species. The descendants then migrate back into the ancestral range. If punctuated equilibria and allopatric speciation did occur, the fossil record would no longer be imperfect. The sharp morphological breaks between ancestors and descendants would mark the breaks of the migration of the descendants.
The distinction between the two theories of evolution provides a new perspective for explaining the history of life. Eldredge and Gould thought this distinction was important because they were trying to persuade the audience to accept punctuated equilibria and see the faults of phyletic gradualism.
The most interesting part of this paper was how the authors used philosophy to support their point of view. “Innocent, unbiased observation is a myth.” Eldredge and Gould argue that people do not encounter facts as data. “All observation is colored by theory and expectation;” scientists have a biased and inadequate picture guiding their thoughts on speciation.
I was confused by some of the figures of Gould’s experiment. I would like to go over figure 5-6 and 5-8 in class.
For more on punctuated equilibria, see Eldredge, N. and Gould, S. 1972. “Punctuated Equilibria: an Alternative to Phyletic Gradualism.” Reprinted from Models in Paleobiology Chapter 5: 82-115.