Did whales gain the ability to live in the water by shedding genes?

humpback whale
Image: Aquatic Adventures

Like stripping down to swim, the ancestors of whales and dolphins may have shed some genes during their transition from being landlubbers to aquatic dwellers.

Ancestors of orcas, bottlenosed dolphins and other cetaceans lost function of at least 85 genes as the animals adapted to live full time in water, researchers report September 25 in Science Advances.

Scientists compared DNA of whales and dolphins with that of other mammals to find 236 genes missing from cetaceans. Of those missing genes, 85 are still present in hippopotamuses, cetaceans’ closest relatives, suggesting that the genes were lost during the land-to-water transition about 50 million years ago.

Cetaceans may have adapted to diving by jettisoning genes involved in regulating blood pressure and blood clotting, and in repairing DNA. DNA undergoes damage from cycles of low and high oxygen as animals dive to deep water and resurface again. One of the lost genes, POLM, encodes a DNA repair enzyme that is error-prone even under the best of circumstances, so getting rid of it may have given cetacean ancestors an advantage. “We think that by losing the sloppiest protein involved, you probably increase the fidelity of DNA repair,” says evolutionary genomicist Michael Hiller.

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Read full, original post: Losing genes may have helped whales’ ancestors adapt to life under the sea

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