More than 150 years after the first Neanderthal was discovered, we still can't agree on whether they were a separate species. Scientists excavate caves, chip flint to make stone tools, and use the very latest DNA sequencing techniques to try to understand them. IDEAS producer Dave Redel digs into the mysteries of the Neanderthals and discovers that knowing them is really about knowing ourselves. Part 2 airs Thursday, April 30.