Comparing neanderthals to homo sapiens

Can Neanderthal DNA help identify what makes humans human?

This is the question Nature and Science magazines are asking (in their November 2006 issues) after paleogenetist Svante Paabo and his team succeeded in extracting DNA from the upper leg bone of a Neanderthal who lived 38,000 years ago. Using a new technique called “pyrosequencing,” Paabo’s team helped decode one million out of the three billion base pairs of the Neanderthal genome, a task that will take at least another two years to complete. But why should scientists be so interested in decoding the genome of a species that became extinct 30,000 years ago? What questions will it help us answer?

1) Did Neanderthals and early Homo sapiens (the species to which we contemporary humans belong) share a common ancestor?

2) Given that Neanderthals were the closest known relative to Homo sapiens and that these two species shared at least 99.5% of their DNA, what are those remaining 0.5% of difference (the specific genes) that make human beings human?

3) If Neanderthals and Homo sapiens diverged around 500,000 to 700,000 years ago and settled in different geographical regions (Neanderthals in Europe and Western Asia around 130,000 years ago and Homo Sapiens in Africa around the same time), and then re-encountered each other 40,000 to 50,000 years ago (when humans spread into Europe and Asia), why did the Neanderthals become extinct 10,000 years later and why did only the humans survive?