History, Evolution, and The Darwin Debate

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More Darwin junk on the left: will the left ever disentangle from Darwinism?

October 11th, 2012 · 2 Comments

This source, which we have discussed and criticized repeatedly has another in the series: http://www.marxist.com/marx-darwin-gould-revolution-of-evolution-pt-4.htm:
You can get the commentary here:
I won’t continue with my bashing of these articles: you can read all that at the link. This article shows clearly where even the punctuated equilibrium goes wrong. Gould/Eldredge didn’t really break with Darwinism. They left the natural selection scenario inside the new paradigm. But that won’t really work. Where is the real evidence here? The evidence shows rapid speciation, why? We don’t know. I don’t think that we can actually generalize about speciation: they are probably many different cases. The diverse speciation of insects is probably not the same process as what we see in hominids.
The term ‘punctuated equilibrium’ needs a new perspective, and gets one in Descent of Man Revisited:
http://descentofmanrevisited.com/DMR_pdf/DMR_Chap_4.pdf has a new take on punctuated equilibrium, which is a neat phrase, better used in a different way.

Punctuated equilibria: a revolution in biology

When Stephen Jay Gould and Niles Eldredge published Punctuated Equilibria: an alternative to phyletic gradualism in 1972, they introduced a new question: if Mayr’s geographic speciation is true, what are the consequences for the speed of evolution? It was like a bomb exploding in the scientific debate. Gould and Eldredge reversed the Synthesis’ view applying the geographic speciation of Ernst Mayr to the interpretation of the fossil records. As they explained:

“The theory of allopatric (or geographic) speciation suggests a different interpretation of paleontological data. If new species arise very rapidly in small, peripherally, isolated local populations, then the great expectation of insensibly graded fossil sequences is a chimera. A new species does not evolve in the area of its ancestors.”[2]

This view on evolution leaves no room for missing links. Breaks in the fossil records reflect the actual geographic speciation over the generations. The fossil records show also the stasis in which founder populations found themselves after they adapted to a new environment. As Gould and Eldredge underline:

“The central concept of allopatric speciation is that new species can arise only when a small local population becomes isolated at the margin of the geographic range of its parent species. Such local populations are termed ‘peripheral isolates’. A peripheral isolate develops into new species if isolating mechanisms evolve that will prevent the re-initiation of gene flow if the new form re-encounters its ancestors at some future time. As a consequence of the allopatric theory, new fossils species do not originate in the placed where their ancestors lived” (Ibid.)

In the theory of Gould and Eldredge, evolution proceeds from quantitative accumulation to qualitative leaps as is clearly recorded by the fossil records. It was a new way of reading the natural history of our planet: in other words, it gave a new tempo and new mode to evolution. Moreover, punctuated equilibria encompassed the previous theory of biological species and geographical species, not by rejecing them completely but by applying to these concepts a dialectical view. Small founder populations and different rhythms marked by fossil records: these are the ingredients of this revolutionary theory.

In the words of the two scientists:

“In summary, we contrast the tenets and predictions of allopatric speciation with the corresponding statements of phyletic gradualism previously given: 1) New species arise by the splitting of lineages; 2) New species develop rapidly; 3) A small sub-population of the ancestral form gives rise to the new species; 4) The new species originates in a very small part of the ancestral species’ geographic extent – in a isolated area at the periphery of the range. These four statements again entail two important consequences: 1) In any local section containing the ancestral species, the fossil record for the descendant’s origin should consist of a sharp morphological break between the two forms. The break marks the migration of the ancestral range. (…) 2) Many breaks in the fossil record are real: they express the way in which evolution occurs, not the fragments of an imperfect record.” (Ibid.)

After the publication of their first work, Gould and Eldredge were often accused of rejecting the core of Darwinism. On the contrary, they gave to it a solid foundation. The theory of punctuated equilibria is based on natural selection because geographical speciation and the biological theory of species are based on natural selection. The new conditions (such as the potential lack of predators in the new environment) in which a small founder population finds itself give a boost to the rhythm of change.

Gould and Eldredge explain that fossil records can actually reflect episodes of acceleration in natural selection as well as the stability of species for long periods of time. Many years later, on the basis of new discoveries in the mechanisms of evolution, Gould and Eldredge were to extend the Darwinian core of natural selection from populations to species. In fact, punctuated equilibria is incompatible with the extrapolation of micro-evolution to macro-evolution made by the Modern Synthesis: taxa formation from plants to mammals requires different mechanisms that are not reducible to micro-evolution that operates on populations. These mechanisms include natural selection, but they are not reducible to it. It is a pluralistic view of evolution based on a principle of emergent properties.

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