So, Guillaume has answered his second letter for Guillaume’s Mailbag. As usual, this will be much more readable at the Darwin Eats Cake site:

Best URL for sharing: http://www.darwineatscake.com/?id=43 Permanent image URL for hotlinking or embedding: http://www.darwineatscake.com/img/comic/43.jpg

Hat-tips go to Alejandro Weinstein for his question, and to Lizzie Foley, for consulting with Guillaume on the answer.

Guillaume also wanted to point out that if armpit hair were not adaptive, then why would Kevin Grennan have included it in this artificial armpit?

The robotic armpit releases “Japanese standard artificial sweat,” which is apparently a thing. Image via CNET.

We leave you now with this music video, which, if Pop Up Video is to be believed, was referred to by its director as a “celebration of the armpit.” Enjoy.