A marine biologist explores the unbelievable evolution of seven different mammal lineages that transitioned back to the sea after 300 million years on land.

00:00 – Marine Mammal Evolution
01:58 – Evolution of Sirenians
03:19 – Vestigial Structures
04:56 – Indohyus, the Missing Link
06:35 – Pakicetus, the First Whale
08:32 – Whale Evolution
10:47 – Basilosaurus, the First Fully Aquatic Whale
14:14 – Evolution of Sea Lions, Seals, and Walruses
15:44 – Thalassocnus, the Aquatic Ground Sloth
17:15 – Evolution of Sea Otters and Polar Bears

The first whales lived about 50 million years ago and resembled wolves with hooves. Over time, their hooves evolved into flippers, their nostrils turned into blowholes, and their bodies streamlined until they became hyper specialized for life in the ocean. But they’re not alone land mammals returned to the ocean at least seven separate times. Two of these ancient lineages went extinct, but five still exist today. Sirenians (manatees and dugongs), cetaceans (whales and dolphins), pinnipeds (seals, sea lions, and walruses), sea otters, and polar bears. Together, these five clades are collectively known as marine mammals.

Sources
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[8] https://www.climatechangenews.com/201…
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[11] https://journals.plos.org/plosone/art…
[12] https://www.sciencenews.org/article/e…
[13] https://www.newscientist.com/article/…
[14] https://royalsocietypublishing.org/do…
[15] https://www.science.org/content/artic…
[16] https://hakaimagazine.com/news/sloths…
[17] https://www.researchgate.net/publicat…
[18] https://www.researchgate.net/publicat…
[19] https://commons.wikimedia.org/wiki/Fi…
[20] • Amazing Antelope – The Water chevrotain di…
[22] • Incredible Dolphin Birth at Dolphin Quest …
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