Quite a number of interesting bits, like cetaceans lost the gene
for saliva.
https://arstechnica.com/science/2022/11/the-evolution-of-whales-from-land-to-sea/
Genomes of cetaceans help tell story of mammals who returned to life
aquatic.
...
But their body plans are just the start of cetaceans’
weirdness. To survive in the sea, they also had to make i
nternal modifications, altering their blood, saliva,
lungs, and skin. Many of those changes aren’t obvious
in fossils, and cetaceans aren’t easily studied in the
lab. Instead it was, once again, genetics that brought
them to light.
With an increasing availability of cetacean genomes,
geneticists can now look for the molecular changes that
accompanied the back-to-water transition. While it’s
impossible to be certain about the influence of any
particular mutation, scientists suspect that many of
the ones they see correspond to adaptations that allow
cetaceans to dive and thrive in the deep blue sea.
...
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