Monday, 22 July 2024
Yet more uncommon descent?
Fossil Friday: Saber-Toothed Tigers Originated Multiple Times
This Fossil Friday features the saber-toothed tiger Smilodon populator from the Pleistocene of Brazil. Just like dinosaurs and mammoths, saber-toothed tigers are among the most iconic prehistoric animals. The La Brea Tar Pits near Los Angeles are just one of the famous fossil localities where well-preserved skeletons of saber-toothed tigers have been found.
A recent study by scientists from the University of Liege (2024) looked into the origin of this peculiar dental trait. Actually, unlike many other instances of biological novelty saber teeth did not appear abruptly and do not represent a morphological discontinuity, but rather show a continuum of sizes and shapes of the canine teeth in cat-like carnivores. This is not so surprising, as the character of saber teeth is not a complex one, but rather just an instance of allometric differential change of size and shape, which might well be within the realm of gradualist Darwinian mechanisms.
Signs of Design
However, there is another phenomenon concerning saber-toothed predators that may suggest design. The comparison of the different saber-toothed cat-like animals shows that they do not form a clade of most closely related forms, so that “sabertooth morphology stands as a classic case of convergence, manifesting recurrently across various vertebrate groups” (Chatar et al. 2024). These include the Miocene Barbourofelidae, the Nimravidae, which lived from the Eocene to the Miocene in Eurasia and North America, and of course the saber-toothed tiger subfamily Machairodontinae among true felids, which had a wide distribution from the Miocene to the Pleistocene. But saber-tooth morphology is also found in gorgonopsid mammal-like reptiles from the Permian period, the marsupial Thylacosmilidae from the Neogene of South America, as well as the machaeroidine Oxyaenidae from the Eocene of Asia and North America.
Convergence is a ubiquitous phenomenon in biology and a genuine problem for Darwinism, which calls for an alternative explanation. This has been recognized by some mainstream scientists such as the famous paleontologist Simon Conway Morris, who authored several books (Conway Morris 2003, 2015) and scientific articles on this subject. The reuse of the same design in different independent instantiations is a typical design pattern in engineering. The same idea is applied whenever it makes sense, in different instantiations
What Causal Mechanism?
To me this suggests that the evolution of saber-toothed cats may well have been gradual as suggested by the new study (Chatar et al. 2024; also see University of Liege 2024) but was rather a teleological, goal-directed process than an unguided neo-Darwinian mechanism of natural selection acting on random variations. This is also supported by the fact that the new study showed that “rapid evolutionary rates emerge as key components in the development of a sabertooth morphology in multiple clades” (Chatar et al. 2024) and “saber-toothed species seemed to show faster changes to skull and jaw shapes earlier in their evolutionary history than species with shorter canines — essentially a ‘recipe’ for evolving into saber-toothed feline-like predators” (Chatar quoted in Smaglik 2024). What causal mechanism accelerated the evolutionary speed? According to evolutionists (Chatar et al. 2024), “a rapid burst at the beginning of the nimravid evolutionary history” just happened, and likewise “machairodontine felids rapidly moved away from the most common cat-like morphology.” No explanations offered, but no intelligence allowed either. Maybe scientists should stop shutting their eyes and ears to what nature wants to tell them.
References
Chatar N, Michaud M, Tamagnini D Fischer V 2024. “Evolutionary patterns of cat-like carnivorans unveil drivers of the sabertooth morphology.” Current Biology 34(11), 2460–2473. DOI: https://doi.org/10.1016/j.cub.2024.04.055
Conway Morris S 2003. Life’s Solution: Inevitable Humans in a Lonely Universe. Cambridge: Cambridge University Press.
Conway Morris S 2015. The Runes of Evolution: How the Universe Became Self-Aware. Templeton Press, West Conshohocken (PA), 528 pp.
Smaglik P 2024. “Saber Teeth are as Mysterious Evolutionarily as They are Iconic Visually.” Discover Magazine May 17, 2024. https://www.discovermagazine.com/the-sciences/saber-teeth-are-as-mysterious-evolutionarily-as-they-are-iconic-visually
University de Liege 2024. “How saber-toothed tigers acquired their long upper canine teeth.” Phys.org May 16, 2024. https://phys.org/news/2024-05-saber-toothed-tigers-upper-canine.html
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