Producer Graham Chedd thought a chat en plein air would add some visual variation from the two-guys-sitting-on-a-couch-type shot that's always easy to get in a professor’s office.

Here are some additional behind-the-scenes photos of the "Human Spark" nighttime campfire shoot with archaeologist Curtis Marean.

In Arizona, Alan and archeologist Curtis Marean had a fireside chat about how modern humans replaced the Neanderthals. Check out this video to see how the scene was made.