One of the lies creationists claim about the Theory of Evolution is that there are no transitional fossils. There are thousands of species in the fossil record that could be considered transitional. The evolutionary lineage of many extant species is well documented, and there are many potential transitional species living today. Moreover, the fossil record of transitional species is well supported by genetic evidence. The fossil record shows the most ancient known ancestor of modern whales was hippo-like. And genetic evidence proves hippos are the closest living land relative of whales. An animal very similar to the earliest known ancestor of whales is still extant. The same is true for seals. The oldest known ancestor of seals was an otter-like animal. And genetic evidence proves the mustelids (a group including weasels, otters, skunks, and badgers) are the closest living land relatives of seals. Present day species of otters and hippos might be transitional species evolving from a terrestrial existence to an even more aquatic life.
Artists’s representation of Puzilla darwini, the oldest known ancestor of modern seals. It is otter-like, and genetic evidence shows mustelids are the closest living relatives of seals.
Artist’s representation of enaliarctos. It clearly has features transitional between a mustelid and a seal.
Allodesmus was yet another evolutionary step between mustelids and seals.
Genetic evidence suggests pinnipeds (seals, sea lions, and walruses) diverged from the other caniformes (a group including bears, dogs, weasels, and raccoons) about 50 million years ago. They diverged from mustelids 46.15 million years ago. The pinnipeds are considered to be a sister group to weasels, skunks, raccoons, and red pandas. The earliest known ancestor of seals dates to 30 million years ago and is known by the scientific name of Puzilla darwini. It’s remarkably otter-like. Other ancestral species of seal include enaliarctos, pteranarctos, allodesmus, desmatophoca, and leptophoca. Genetic evidence suggests ancestors of earless seals diverged from ancestors of sea lions 25 million years ago. The oldest fossils of walruses date to 18-16 million years ago. The extinction rate for walruses exceeded the speciation rate between 12-6 million years ago. Scientists don’t know whether this is due to fluctuating sea levels or competition with newly evolved species of sea lions. Species with near global distribution are more resistant to extinction.
Today, there are 3 families of seals and 33 species. These include 18 species of true seals (the phocidae), 14 species of sea lions and fur seals (the otaridae), and 1 species of walrus (the odenibae).
References:
Park, T.; et. al.
“Charting the Course of Pinniped Evolution: Insights from Molecular Phylogeny and Fossil Interpretation”
Evolution 78 (7) July 2024
Paterson, R.; N. Rybcynski, N. Kohno, H. Mudd
“A Total Evidence Phylogenetic Analysis of Pinniped Phylogeny and the Possibility of Parallel Evolution”
Frontiers Ecology and Evolution January 2020
https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2019.00457/full
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