Episode 231 - Back to the Water (Secondarily Aquatic Vertebrates)

The Common Descent Podcast

Common Descent

Science, Natural Sciences, Education, Earth Sciences, Science:natural Sciences

4.8 • 764 Ratings

🗓️ 23 November 2025

⏱️ 163 minutes

🔗️ Recording | iTunes | RSS

🧾️ Download transcript

Summary

Nearly 400 million years ago, an unusual group of fish gave rise to the first land-dwelling vertebrates. Since then, their descendants have repeatedly moved back into the water. This episode, we explore the many ways these species adapt to the challenges of turning a terrestrial body into one that can survive at sea, and we investigate some of the most famous and confusing cases from the fossil record. In the news: post-extinction oceans, croc eggs, damaged dino tails, and meat-eating dung beetles. Time markers:Intro & Announcements: 00:00:00News: 00:05:45 Main discussion, Part 1: 00:40:15Main discussion, Part 2: 01:31:35Patron question: 02:30:30 Check out our website for this episode’s blog post and more: http://commondescentpodcast.com/ Join us on Patreon to support the podcast and enjoy bonus content: https://www.patreon.com/commondescentpodcast Got a topic you want to hear about? Submit your episode request here: https://commondescentpodcast.com/request-a-topic/ Lots more ways to connect with us: https://linktr.ee/common_descent The Intro and Outro music is “On the Origin of Species” by Protodome. More music like this at http://ocremix.org Musical Interludes are "Professor Umlaut" by Kevin MacLeod (incompetech.com). Licensed under Creative Commons: By Attribution 3.0 http://creativecommons.org/licenses/by/3.0

Transcript

Click on a timestamp to play from that location

0:00.0	You're listening to the Common Descent Podcast.
0:19.0	Hello, David. Hello, Will.
0:21.9	And hello, listeners.
0:23.5	Welcome to episode 231 of the Common Descent Podcast.
0:29.7	This episode, we are talking about secondarily aquatic vertebrates.
0:35.0	Yes, vertebrate animals that went back to the water.
0:39.4	That mist being wet and getting to swim.
0:42.6	Tired of being in the sun.
0:44.4	I feel it.
0:45.4	I get it.
0:45.8	This is whales, seals, sea turtles, all of the things that went out of their way to evolve to be great at living on land and then
0:58.0	decided they were having none of it.
1:00.0	Decided it was overrated and Tectolic made a terrible mistake.
1:04.0	Yes.
1:05.0	It was only a fish.
1:07.0	These were, if you've seen the meme of people being like, I know who to blame for all of my problems, and then it's a picture of Tictolic, yes.
1:14.6	These were the first ones who had that feeling. These were the first vertebrates.
1:20.2	In this episode, we will discuss what it means to be secondary aquatic, what it takes, the adaptations, the difficulties, the challenges to going back
1:29.6	to a life in the water, as well as how we recognize it in the fossil record, and what evolutionary
1:35.5	trends we tend to see in the evolution of secondarily aquatic features. This will be a ton of fun with a bunch of cool examples,
1:46.0	and we are discussing it because it was requested quite a bit.
1:50.3	We got requests for this topic from Hans, Matthew, Anna, Richard, Drew, and Teo Rannosaurus.
	...

Please login to see the full transcript.

Previous episode | Next episode

Disclaimer: The podcast and artwork embedded on this page are from Common Descent, and are the property of its owner and not affiliated with or endorsed by Tapesearch.

Generated transcripts are the property of Common Descent and are distributed freely under the Fair Use doctrine. Transcripts generated by Tapesearch are not guaranteed to be accurate.