[Varda]

Fossilized doesn't always mean mineralized. It's more like preserved. This link has an article that talks a little about how they extracted the DNA (hope it comes up for you)- Researchers, led by UO archaeologist, find pre-Clovis human DNA

[allmendream]

They also did mitochondrial DNA which makes it much easier to get a good sample and arrive at a consensus sequence.

Genomic DNA is only one copy per cell. Mitochondrial DNA is in thousands of copies per cell.