What is a species? That's not a simple question.
And it's even harder to answer after you've had a few.
Intrepid science journalist Charles Q. Choi takes inspiration from both the Drunk History series of videos and a really awful lot of whiskey to try and help you better understand a scientific concept (and also the finer points of orc biology). This was an idea I had, which came together with the help of several science journalist friends during the Science Online conference back in January. I'm still impressed with how accurate Charles was on the science while in that state. I can't speak to the Tolkien mythology.
Video Link (Note: This seems to play softly on some computers. If you're having trouble hearing it, plug in headphones or turn up your speakers.)
Thanks to Rose Eveleth, Colin Schultz, and Jennifer Honn — whose work on editing and producing this video was invaluable. Also thanks to John Rennie, Steve Ashley, Olivia Koski, Maki Naro, and Stephen Granade — whose input and assistance made this possible. And, of course, special thanks to Charles, who really was fully recovered by the next morning.