Whale evolution has always fascinated me, ever since I learned that their evolutionary path took them from sea to land and then back to the sea. Here’s an animation showing how the land-to-sea-again transition may have occurred.
Scientists have now learned about a new aspect of this transition in the baleen found in the jaws of whales.
If you observe a feeding fin, blue or humpback whale, you are likely to catch a glimpse of the bristles of baleen that fill its gaping jaws. Baleen is unlike any other feeding structure on the planet. Made of keratin, the same material as hair and finger nails, baleen hangs from the roof of a whale’s mouth and is used to filter small fish and crustaceans from large gulps of water. As water rushes into the mouth of a whale, the small creatures easily pass through the comb-like bristles, but once a whale’s mouth is full of water, it flushes the water back out, trapping the tiny creatures in the wall of baleen to be swallowed whole.
Scientists don’t know how or when baleen evolved, but the recent discovery of an ancient whale fossil—roughly 30 to 33 million years old—hidden in the collections of the Smithsonian National Museum of Natural History may hold a critical clue.
Scientists have speculated that baleen may have come to replace teeth and the fossil they studied seems to have had both, making it a transitional fossil.
With such a unique method for feeding, it is only logical to ask why this whale would evolve in such a way. What could be the advantage to losing an important feeding tool like teeth?`
First, teeth are expensive. It takes a lot of energy an d resources to build teeth with strong enamel. Slurping food is much more economical when soft food is readily available. Second, this whale lived at a time in Earth’s history when the environment was rapidly changing. As Antarctica broke away from South America at the end of the Eocene, the ocean’s currents were disrupted. Now, with Antarctica alone, a massive current encircles the continent—a change that had massive implications for both atmospheric and ocean temperatures around the globe. While it remains unclear as to how this might specifically have impacted whales, what is clear is that the change in Earth’s climate was a spark that ignited dramatic evolutionary change.