What remains is not intact DNA molecules that can be straightforwardly extracted and sequenced, but highly fragmented material with chemical modifications that complicate analysis.

The method developed by Eske Willerslev’s group and applied to Sitting Bull’s hair was specifically designed to address this kind of badly degraded material.

Willerslev is a Danish evolutionary geneticist at the University of Cambridge and the University of Copenhagen who has done extensive work on ancient DNA — the recovery and analysis of genetic material from archaeological specimens, permafrost-preserved organisms, and other sources where DNA has survived in degraded form for long periods.

His laboratory has been at the forefront of developing techniques for extracting and interpreting genetic information that would be inaccessible to standard methods.