What if I told you that, more than two billion years ago, some tiny living thing started to live inside another living thing … and never left? And now, the descendants of both of those things are in you?
Aired:
01/14/18
| Expires: | Runtime: 7m 39s
You are leaving GBH.org
You are leaving gbh.org and going to a web page that is not owned by GBH. If you are streaming, your experience will be interrupted.