- The coelacanths are an ancient group of lobe-finned fishes, with weird appendages that take the form of bony, fleshy, muscular stalks. They’re well-represented in the fossil record all the way back to the Devonian period, some 390 million years ago. However, about 66 million years ago – the time of the dinosaurs’ demise – coelacanths disappear completely. It looked like they went extinct. Then, in 1938, someone caught a coelacanth in a fishing net off the coast of South Africa.
- The lesson here is that the absence of evidence – in this case, the lack of coelacanth fossils – is not the same as evidence of an absence. Take a kookier example. There’s a subculture of ‘cryptozoologists’ who believe that populations of pterodactyls are hiding out in remote parts of the globe, such as Papua New Guinea or the Brazilian rainforest. Pterosaurs, too, disappeared from the fossil record around 66 million years ago, and there is no proof that any of them exist today. Should we apply the same test as for the coelacanths? Or in this case, for some reason, does the absence of evidence amount to the same thing as the evidence of an absence?
- The case of the coelacanth and the pterodactyl are similar in one respect. Both fossils have been missing for the past 66 million years. But for pterosaurs, the best explanation is just that the animals went extinct. For the coelacanth, the message is more complex. Accounting for the gap might invoke the small population size, when and how fossilisation occurs in marine environments, and the fact that much of the rock on the ocean floor is quite young. For both creatures, at least one thing is clear: what doesn’t fossilise is often as revealing as what does.
For the full text, see Aeon: Currie - The missing fossils matter as much as the ones we have found.
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