Ancient footprints in New Mexico raise questions about when humans inhabited North America
16:42
The world's most heavily debated footprints
7:39
Discovery of 2-million-year-old DNA in Greenland reveals new details about ancient life
17:09
The Secrets of the Oldest Footprints Ever Found
14:29
99 Years Later... We Solved It
12:06
Why are these 32 symbols found in caves all over Europe | Genevieve von Petzinger | TED
9:20
Researchers race to answer questions about the unintended consequences of wind energy
53:11
Ice Age Footprints (FULL SPECIAL) | NOVA | PBS America
55:40