The other Night I watched a very interesting documentary on CuriosityStream about whales. “Whale Wisdom” is an awesome documentary that explores the secret life of whales and delves into their incredible problem solving skills, complex family structures, and emotions, and to top it all off the documentary is narrated by Sir David Attenborough. This documentary is incredible and I strongly urge anyone reading this to watch it because whales are amazing creatures. However, arguably the most interesting fact about whales was not even covered in this documentary. Did you know that whales evolved from terrestrial (land) mammals who went back into the sea? This fact has fascinated me since I learned about whale evolution in geoscience my sophomore year of college.
I link to all of my sources throughout the blog and I strongly urge you to check them out if you’re also very interested in whale evolution. My primary source of information is an incredibly well researched and informative episode of PBS Eons.
As weird as it may sound, all Cetaceans (whales, dolphins, and porpoises) are the descendants of terrestrial mammals who decided to go back into the water. This is such a wild fact because all terrestrial animals, particularly mammals, are the descendants of the first tetrapods who left the oceans for a life on land around 375 million years ago. It's funny to think that about 50 million years ago, early Cetaceans decided to reverse course and go back to a life underwater.
The last common ancestor of the Cetaceans was a 47 million year old hoofed deer-like creature the size of a house cat named Indohyus. Although Indohyus was not a Cetacean, it had a specialized ear bone designed for hearing underwater that is only found in whales . We know that the Idohyus was not a Cetacean because it had a very specific ankle bone that is only found in Artiodactyls (hippos, deer, pigs), which suggests that Cetaceans evolved from Artiodactyls. The Indohyus is an interesting transitional fossil that shows us where the Cetaceans split off from the Artiodactyls around 50 million years ago.
Another key species in the evolutionary story of the whale is the Ambulocetus, which was an amphibious species of Cetacean. The name Ambulocetus literally translates to “walking, swimming whale.” This creature lived around 48 million years ago in river deltas and occupied the same ecological niche as the alligator and crocodile. This is a really cool fossil because it shows us how the transition from terrestrial Cetaceans to aquatic ones occurred. Check out this link for a really cool animation of the Cetaceans evolutionary journey from land to sea.
While scientists are still uncertain why Cetaceans moved from a life on land to a life in the sea, there are a few hypotheses. The first hypothesis suggests that 40 million years ago there were fewer predators in the water, making it safer for the Cetaceans. Another hypothesis suggests that prey was more abundant in the water and there less competition, making it advantageous for early Cetaceans to become amphibious. While we don’t know for sure, it was likely a mix of these two hypotheses and possibly some other unknown factors.
Unlike my blogs about cryptozoology, I am not going to provide my two-sense on this issue because the experts know infinitely more than I do and I honestly don’t think I can add anything significant after reading just a few articles and watching two videos. All I will say is that whales and other Cetaceans are majestic creatures, with a very strange past, that should be protected at all costs.
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