I’ve been reading the second edition of Michael Benton’s, When Life Nearly Died: The Greatest Mass Extinction of All Time, which tells of what we know of the Permian extinction prior to the rise of the dinosaurs.
Unlike the Cretaceous extinction that spelled doom for the dinosaurs (with a few bird-like exceptions), the Permian extinction killed off 90% of life on earth. It’s the most devastating extinction to date and one which our ancestry almost didn’t live through.
When discussing the Permian extinction and the history of its discovery, one has to inevitably talk about some of the great English and French natural philosophers of the late Georgian and Victorian eras in order to understand why evidence for the Permian extinction was known but remained unrecognized well into the late 20th century.
Many natural philosophers of the late Georgian period were Christian, and while they didn’t generally hold to a literal interpretation of the Biblical, Genesis, they did nevertheless presume that a great flood had occurred that would have left evidence of massive death in the fossil record.
One such diluvialist was the French scientist, George Cuvier. Cuvier was an exceptional anatomist and was essentially the inventor of what we now know as Comparative Anatomy– which is the study of physical similarities and differences across species.
The French naturalist, Georges Cuvier (1769-1832).
In part because of his belief in the great flood, Cuvier was a proponent of Catastrophism, which is the theory that geological change is not gradual but has occurred in catastrophic sputters and spurts throughout historical time.
It was apparent to the English geologist, Charles Lyell, however, that there was evidence in the geologic record that earth’s revolutions can and do occur in a gradual manner as well. Lyell observed, for instance, on a tour of Italy that the ruins of the Temple of Serapis provided a perfect example of exactly this. Originally, the temple had been constructed during the age of the Roman Empire but had over time sunk below sea level, only to later rise above it again. In Lyell’s age, the tops of the pillar ruins showed dark rings, which were evidence of mollusk holes and the slow upheaval of geologic change. He provided an image of the ruins in his Principles.
The ruins of the Temple of Serapis.
Lyell’s theory was known as Uniformitarianism and, according to Benton, proposed several things (p. 64):
- The laws of nature are constant throughout time.
- Scientists should use observations of modern phenomena to interpret the past.
- Processes in the past occurred at the same rate they do today. (This precludes the use of major catastrophes to explain these phenomena.)
- Geologic change occurs cyclically rather than linearly, which is known as “nonprogressionism.”
The first two of Lyell’s ideas about uniformity are sound ones that all scientists today should agree with. The latter two, however, were Lyellian assumptions, namely that cataclysmic events could not be used to explain geologic change and that, essentially, there was no progression of history but it was instead cyclical. (Both Lyell and Cuvier didn’t believe in the extinction of entire species but believed instead in their constancy as an ordained creation of God.)
Although Cuvier was incorrect that all geological change is the result of catastrophes, we now know that Lyell was equally as incorrect in presuming that catastrophes never occurred to effect the course of life on earth.
The geologist, Charles Lyell (1797-1875).
Unfortunately, Lyell’s Principles was far more influential to the field of Geology than was Cuvier’s work. This was in part due to European and British perceptions of the French Revolution and especially of the Reign of Terror, after which many “French” ideas were deemed revolutionary and potentially dangerous. Therefore, while Catastrophism became known as decidedly French, Uniformitarianism was inherently English and “sensible”.
According to the author, Michael Benton, even during his training in the 1970s, geologic hypotheses invoking major catastrophes were thoroughly frowned upon and it wasn’t until a decade later that slowly scientists began to accept evidence that major extinction events have occurred in earth’s history that have severely impacted life on earth. There has been only a single massive extinction, the Permian, but there have been several intermediate extinctions, including the Cretaceous that led to the rise of mammals, and there have been many small extinctions littering our historical past (and, undoubtedly, our future).
So, as Cuvier would have it, geological evolution does indeed occur in sputters and spurts, yet it also occurs in a gradual, uniform Lyellian way. Both men were partly right even though history has remembered Lyell more kindly.
Of relevance to our own fates, geological knowledge gives us the foresight to understand that the recent human past has been blessed by a time of relative geological and climate quiet. However, in spite of how much we may fear to admit it, catastrophic change is inevitable and part of the rich and turbulent history of life on earth. While we shouldn’t work to usher such change in any sooner than need be, we must also admit to ourselves that it is coming.