Plants and Animals

Fossilized Tooth Sheds Light On Whales' Evolutionary History

Today, baleen whales have a reputation for being gentle giants, but new research shows this wasn’t always the case. In fact, the teeth of ancient whales far more closely resemble those of an African lion than those of 21st-century blue whales. 

Whales can be split into two categories: those with teeth and those with baleen, a tough but flexible material made of keratin that works a bit like a comb to filter prey from the water. In the first category, you’ll find killer whales, sperm whales, and beluga whales. In the second, you have blue whales, southern right whales, and humpbacks. 

How baleen developed has been something of a mystery. Some scientists suggest that ancient baleen whales ate food in the same way crabeater seals and leopard seals do today. That is their teeth were shaped to form a zig-zag when shut. This would have worked like a sieve, trapping food inside while letting water move in and out of the mouth. 

But this theory has now been debunked by a study published in Biology Letters. 

Paleontologists at Museums Victoria and Monash University in Melbourne, Australia, created 3D digital models to compare the fossilized tooth of a prehistoric whale (a janjucetus) with the teeth of modern-day mammals. They discovered that the teeth of ancient baleen whales were much sharper than those of baleen whales today, and are almost as sharp as an African lion’s. This, they say, suggests that the ancient beasts were not gentle giants, but predators who used their teeth to kill and chew their prey.

“These results are the first to show that ancient baleen whales had extremely sharp teeth with one function – cutting the flesh of their prey,” explained Erich Fitzgerald, Museums Victoria’s senior curator of vertebrate palaeontology. “Contrary to what many people thought, whales never used their teeth as a sieve, and instead evolved their signature filter feeding technique later – maybe after their teeth had already been lost.”

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