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Photo: 5-week-old human embryo showing tail. Credit: Ed Uthman, Wikimedia Commons

Animals

How Humans Lost Their Tail, Twice

You started off your life with a tail, but now just have a tailbone. This is why that happened.

December 5, 2016
12:00 PM EST
Illustration: The early double-tailed fish Aetheretmon swimming alongside a singled-tailed modern pufferfish and an early tetrapod in a 350-million-year old river. Credit: John Megahan