About 50 million years ago, dog-like mammals returned to the seas, eventually evolving into whales and dolphins.
Around then, too, an early cousin of elephants took the plunge, giving rise to manatees and dugongs.
A version of this article appeared in the print edition of The Straits Times on August 16, 2018, with the headline 'Marine mammals have lost a gene they may now desperately need'. Print Edition | Subscribe
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