We’ve already brought back DNA from extinct species. Not we are recovering DNA from ancient human races:
Viking DNA Extracted From 1,000 Year Old Skeleton | Scientific Blogging
Analysis of DNA from the remains of ancient humans provides valuable insights into such important questions as the origin of genetic diseases, migration patterns of our forefathers and tribal and family patterns.
Unfortunately, severe problems connected with the retrieval and analysis of DNA from ancient organisms (like the scarcity of intact molecules) are further aggravated in the case of ancient humans. This is because of the great risk of contamination with abundant DNA from modern humans. Humans, then, are involved at all steps, from excavation to laboratory analyses. This means that many previous results have subsequently been disputed as attributed to the presence of contaminant DNA, and some researchers even claim that it is impossible to obtain reliable results with ancient human DNA.
Extremely cool. There’s no reason to be limited to the human biodiversity that currently exists on the planet. While evolution has doubtless optimized many modern humans for life in the modern world, there doubtless were good variants in the past that were lost either before they became valuable or because of genetic drift.