Larry Engel and the crew head to Stony Brook, where Alan Alda gets a lesson in primitive weapon- and bead-making from experimental archaeologist John Shea.

Alan enters the lab at Yerkes hoping to learn about chimpanzees and facial recognition. But instead, the chimps show Alan and the crew who's boss.

Psychologist Vicky Horner discusses research into chimpanzee cultural transmission. Do chimps have "culture" like humans?

Can you use Google and Twitter? If so, wrangle with these trivia questions to receive free science DVDs.

See what other people said they think makes us human. Then, share YOUR spark in text, photos, artwork, or video.

Submit your drawings, photos, videos, or text that answer the question, "What makes us human?" Your responses will be posted on this web site, and a selection will appear on-screen during the broadcast!

Amanda Henry showed us how she very gently scrapes dental plaque from the Skhul 5 skull’s molars to find out what our ancestors may have eaten.

We went to the North Carolina Zoo to meet the chimpanzees -- and evolutionary anthropologist Brian Hare. Here's what happened...

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.

Check out these behind-the-scenes photos from our day filming with Helen Neville and colleagues at the Brain Development Lab at the University of Oregon.