Before the whales faded, they were toothless – Quartz

Whales about 33 million years ago were not polite guests. They lacked teeth, so like powerful prehistoric aspirators, they sucked entire fish and squid, swallowing them whole.

The image of a gummy and toothless whale disrupts the current evolutionary theories that the teeth that ancient whales had to chew on their food turned into baleen – straw-shaped keratin structures that filter prey. Tiny, like krill, of sea water. However, recently discovered remains belonging to an ancient whale species suggest that whales initially lost all their teeth, and then evolved to become baleen whales. Researchers led by a team from George Mason University in Virginia described their findings in an article published today (November 29) in the journal Current Biology.

The researchers examined the remains of an ancient whale discovered in Oregon in 1977 by an amateur fossil collector, which was stored for decades in a Maryland warehouse. To this day, all we know about this whale is that it lived about 33 million years ago; the scientists called him Maiabalaena, or "whale mother".

When George Mason's team was finally able to examine the bones, she was surprised to find a jaw and throat structure more compatible with sucking rather than biting or chewing. Because Maiabalaena The team felt it was an intermediate step in the history of the whale. She lived 55 million years ago and the emergence of baleen whales, appeared 25 million years ago.

Peredo et al., 2018 / Screen capture

Maibalaena According to Carlos Peredo, a graduate student in paleontology and lead author of the book, whales living at that time did not need teeth to live long enough to reproduce.

Ancestors to Maibalaena had plenty of teeth to catch and chew on his prey. At one point, however, they began to eat smaller and smaller animals requiring less chewing, which meant that toothed whales were no more likely to reproduce than animals without. Ultimately, however, teeth may have hindered suction feeding, or perhaps toothless whales need less food than toothed whales during maturation, making them more likely to survive. As more and more toothless survivors were breeding, the whales had completely lost their teeth.

Peredo postulates that the baleen have evolved to solve a problem that faced vacuum cleaners: absorbing too much salt water during meals. Baleen eliminates krill and other types of small prey to swallow, while allowing the whale to evacuate any excess water.

This work shows that evolution does not necessarily follow a rectilinear path, but that it progresses in favor of the animals that it takes to live long enough to reproduce in their environment. Inevitably, modern baleen whales will have to evolve again to keep pace with their ocean dwellings, which are changing rapidly due to warmer waters resulting from climate change. Marine biologists still do not know how these changes will affect their food sources or their physiology. Although evolution can occur in the space of 100 generations (a wink, in biological terms), some baleen whales live more than a century. With such a long life, it is unclear if they will evolve quickly enough to keep pace with their changing environment.