While evolution became a big deal in 1859 with the publication of Darwin’s Origin, there were of course people who had the idea of evolutionary change before him. One of these was Jean-Baptiste Lamarck (1744-1839), who suggested that organisms had evolved over long periods of time, but who has become infamous for suggesting that that evolution involved phenotypic changes according to an animal’s “will” that altered heredity via use and disuse of parts (the giraffe evolving a long neck by stretching it to reach high branches is the classic example).
In contrast, his fellow Frenchman, the influential zoologist and naturalist Georges Cuvier (1769-1832) argues for the “fixity of species”: because species’ parts were optimally adapted to each other, species could not and did not change over time.
Their conflicting view of evolution, and how they were subject to a test, albeit a flawed one, is described in this article in the new PLoS Biology (click on the screenshot, reference below and pdf is here).
The tale is brief. When Napoleon and his army invaded Egypt at the end of the 18th century, they found and recovered many animal mummies, which included not only the famous cats, but also jackals, dogs, snakes, the sacred ibis, and of course humans. Many of these were brought back to Paris and put in museums. And there there were lots of them: the paper notes that the catacombs at one site alone contained 4 million mummies of the Sacred Ibis. That bird became the bone of contention between Lamarck and Cuvier.
First, here’s a picture of the extant African Sacred Ibis (Threskiornis aethiopicus), considered sacred as a representation of the Egyptian god Thoth, who, among his other attributes, maintained the Universe. I put a picture of Thoth below the Ibis; his head is that of the bird:
And here are some mummified Ibises (their wrapped bodies were put in pots); the caption is from the paper.
The presence of 3,000 year old Ibises afforded a one-way test of whether the bird had evolved. If the mummified Ibises were very different from present-day ones, then one might claim that evolutionary change had occurred. If not, then Cuvier would claim that their stasis supported his view that species were fixed. (It’s a one-way test because the finding of “no change” could still be consistent with slow evolution.)
After a bit of a mixup between the Sacred Ibis and a similar bird, the yellow-billed stork (Mycteria ibis), Cuvier managed to show that the mummies he studied were indeed the same species as the African Sacred Ibis of today. But had they changed at all? He measured the body parts of mummy skeletons and modern ibises, and the paper gives the data (an assertion, really, with my emphasis below):
Based on these measurements, Cuvier correctly established that the mummies were not storks. He determined that the mummified birds matched the unclassified birds from the museum. Cuvier went on to name these birds Numenius ibis, and they have subsequently been reclassified as T. aethiopicus (Sacred Ibis). Cuvier also recovered a few uniquely shaped black feathers from a mummy that provided further evidence for his identification of the mummified birds as ibis. To Cuvier’s knowledge, these distinctive black feathers were a characteristic of the genus Numenius . Cuvier preserved these feathers for future examination as “a remarkable monument of antiquity and a peremptory proof of the identity of species”.
The measurements of the mummified bones were not a perfect match with those taken from the museum specimens of Sacred Ibis. However, the measurements between the ancient material and the then-contemporary Sacred Ibis were similar, and Cuvier concluded that no detectable anatomical changes had occurred over time. This made him the first to test the idea of evolution.
The debate went on at the French Academy of Science, and Cuvier properly replied that, after all, these birds were only 3,000 years old, and that wasn’t enough time to expect much evolutionary change.
The results thus seem inconclusive, but Cuvier’s objection was reasonable. I’m not sure what the upshot was among zoologists, as the authors don’t report this, but it’s really a one-way test of evolution, and not a very good one given that there was “not a perfect match” between the measurements of extant versus mummified ibises. “Similar” is not “identical”, and some evolution might indeed have taken place based on the measurements.
Still, this is an interesting episode in the history of evolutionary biology, and a “test” of evolution that preceded Darwin by several decades. What surprises me is that this episode is well known to historians of science and to some evolutionists (I’m not among the informed), and I don’t really see a good reason for publishing it in a premier biology journal. Still, I was glad to learn the story, and perhaps you will be, too.
Curtis C, Millar CD, Lambert DM (2018) The Sacred Ibis debate: The first test of evolution. PLOS Biology 16(9): e2005558. https://doi.org/10.1371/journal.pbio.2005558