animal anatomy

Once upon a time, there were no anuses. These ingenious organs allowed our primordial ancestors to grow bigger and more complex, but scientists still don’t understand how they evolved. And they’re still grasping at a mystery that literally surrounds it: Why is the human butt so big? For more go to http://vox.com/unexplainable It's a great place to sign up for our newsletter, view show transcripts, and read more about the topics on our show. Also email us! unexplainable@vox.com We read every email. Support Unexplainable by making a financial contribution to Vox! bit.ly/givepodcasts Learn more about your ad choices. Visit podcastchoices.com/adchoices

The anus is an evolutionary marvel. But how and when did this organ evolve into what it is today? Today on Short Wave, Maddie gets to the bottom of these questions with The Atlantic's science writer Katherine Wu.

For more of Katherine's reporting, check out 'The Body's Most Embarrassing Organ Is an Evolutionary Marvel' from The Atlantic.

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