frosted weeds, giant leaps of evolution versus punctuated equilibrium

Nu couché- Les femmes d’Alger (Delacroix) by Picasso 1954

There were four versions – all part of a series – of this painting. From a Babelfish translation of a pamphlet available from The Louvre,

Throughout its life, since its academic training with last years of its life, while passing by the revolution cubist and the neo-classic period, Picasso nourishes painting of the past. In the Fifties, it paints three great series of variations d’ after chiefs-d’ work of the last one: women of Algiers according to Delacroix in 1954, Menines according to Velasquez in 1957…

If you have a few million they’re listed in art auction catalogs as versions O, H, M and K. The painting is a woman in the technical sense, but it is also a self-portrait in its depiction of Picasso’s personal torment over his masculine and feminine side.

frosted weeds

Evolution may take giant leaps

A new study of thousands of species of plants and animals suggests new species may arise from rare events instead of through an accumulation of small changes made in response to changes in the environment.

The traditionally accepted idea of species evolving through gradual changes is the Red Queen hypothesis, named after a character in Alice in Wonderland, who explains to Alice that “it takes all the running you can do, to keep in the same place.” The hypothesis, that species continually change and adapt to compete with co-evolving species and retain their ecological niche, was proposed in 1973 by Leigh Van Valen.

[   ]…The researchers then compared four models of speciation to determine which best accounted for the rate of speciation actually found. The Red Queen hypothesis, of species arising as a result of an accumulation of small changes, fitted only eight percent of the evolutionary trees. A model in which species arise from single rare events fitted eighty percent of the trees.

The late Professor of science history and paleontologist Stephen Jay Gould, along with paleontologist Niles Eldredge actually came to a similar conclusion years ago in a sub-theory of evolution called Punctuated equilibrium,

Punctuated equilibrium is a theory in evolutionary biology which proposes that most sexually reproducing species will experience little evolutionary change for most of their geological history (in an extended state called stasis). When evolution occurs, it is localized in rare, rapid events of branching speciation (called cladogenesis). Cladogenesis is simply the process by which species split into two distinct species, rather than one species gradually transforming into another. Thus, “punctuated equilibria is a model for discontinuous tempos of change (in) the process of speciation and the deployment of species in geological time.”[1]

Punctuated equilibrium is commonly contrasted against the theory of phyletic gradualism, which states that evolution generally occurs uniformly and by the steady and gradual transformation of whole lineages (anagenesis). In this view, evolution is seen as generally smooth and continuous.

One criticism that was made regarding Eldredge and Gould was the misconception of time frames. They never proposed that species suddenly disappeared and new ones evolved, say due to a catastrophic geological event. Their concept of time saw a 100,000 years as a punctuation. It makes sense in that fossil species are found corresponding to millions of years than suddenly disappear. Where Dr Pagel is probably off is his claim that speciation is not the result of  millions of years of small events. Darwin, who went by the fossil record of his time saw a kind of continuous gradualism. Eldredge and Gould saw that, but included sudden changes or relatively sudden in terms geological time – hundreds of millions of years. Punctuated equilibrium saw a continuum of biological types that even once they stopped evolving stayed around a phenotypic mean. If Pagel thinks gradualism is a dead concept he is going have to have more evidence then missing some transitional types. Its weird that like Eldredge and Gould, Pagel does acknowledge that big climate shifts, mutations and geological changes ( like suddenly isolating a species on an island) play a integral role in evolution, but discounts gradualism altogether.


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