|Punctuated evolution, (i.e. absence of evidence for speciation). Old species disappear, and new species appear,|
Five score and thirteen years after Origin of Species, Darwinism faced a crisis.
Darwin predicted that evolution by random heritable variation and natural selection would be gradual. The progressive accumulation of beneficial mutations would eventually result in reproductive isolation, and speciation. The fossil record should be full of intermediates. In fact, Darwin's theory posits that all living things are intermediates, links between ancestral species and future species.
The problem was the evidence. Nearly all fossils showed the same pattern: millions and millions of years of stasis, without evidence for evolution, then sudden disappearance, with replacement by a new species. No intermediates.
By the 1970's, the crisis was acute. How to rescue Darwin's theory from its worst threat-- not creationists, but lack of evidence. How could Darwinism-- gradual evolutionary change by random heritable variation and natural selection-- be squared with the lack of fossil evidence for gradual evolutionary change leading to new species?
Two Darwinists hit upon a solution. A solution of genius.
In 1972, Harvard evolutionary biologists Steven Jay Gould and Niles Eldredge published Punctuated equilibria: the tempo and mode of evolution reconsidered. The theory of punctuated equilibrium posits that species remain relatively fixed-- in stasis-- for millions of years. Then, a catastrophic event causes extinction of the species, and another nearby small population of individuals, who are undergoing rapid evolution, move into the niche abandoned by the extinct species. The small population, having already quickly evolved, flourishes, remaining and fossilizing for millions of years, until it too undergoes a catastrophic extinction, and is replaced by another small rapidly-evolved population, etc., etc.
The salient feature of the fossil record left by this evolutionary musical-chairs is that evolution is never observed. Speciation occurs in tiny populations too small to leave enough fossils to be found. The fossil record records replacement of species that have evolved rapidly, without leaving evidence of their evolution. If punctuated evolution were true, speciation in the fossil record would never be detected, only appearance, stasis, and disappearance of species. If punctuated evolution were true, evidence for speciation in the fossil record would not be found.
Which fit the fossil evidence perfectly.
Gould and Eldredge's theory calls to mind the conundrum faced by physicists in the late 19th century, who were confronted by the failure of the Michaelson-Morely experiment to detect the 'ether wind' through which the earth moved. Michaelson and Morely used a complex array of mirrors to attempt to demonstrate a doppler effect on the speed of light, according to the direction in which the light traveled with respect to the revolution of the earth around the sun. When the light was propagated into the ether wind, it was anticipated that it would propagate more slowly; with the wind, more rapidly.
In fact, regardless of the direction of the light, its speed was unchanged. The ether wind didn't seem to exist.
Some scientists, in an effort to salvage the ether wind, proposed that the measuring instruments were contracted and stretched by the wind to the same proportion the light was impeded or boosted. This would explain the absence of evidence for the wind.
Other scientists, wags, pointed out that this explanation rendered the ether wind undetectable. Absence of evidence for the wind would then be evidence for the wind.
Physicists were smart folks without an agenda, except the search for truth, and the ether hypothesis was discarded.
Not so in evolutionary biology. The theory of punctuated equilibrium is able to explain a fossil record-- a record of prolonged stasis interrupted by (geologically) instantaneous disappearance of one species and appearance of another-- as arising by a Darwinian mechanism. Even better, the actual Darwinian evolution could never be observed, because the actual evolution of species via intermediates occurred too quickly in populations too tiny to leave a record.
The evidence for punctuated equilibrium, then, is the absence of evidence.
How could you not love this stuff?