How did animals first make the giant step from water to land? Evolutionary biologist Sean B. Carroll explains how the discovery of Tiktaalik—a fossil with both fish and limb-like features—revealed a key moment in evolution.

For more, check out the <a href="https://www.wgbh.org/podcasts/particles-of-thought/evolution-of-new-species-venom-wings-and-more-extended-interview-with-sean-b-carroll">extended interview </a>with Sean B. Carroll.

Learn more about <a href="https://www.pbs.org/wgbh/nova/">NOVA</a> and subscribe to our <a href="https://www.youtube.com/channel/UCjHz5SVHeMT0AViCYZvsGDA">YouTube </a>channel.

The Air You Breathe Is Bacteria Poop | Peter Girguis

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