Hardened plaque from 700-year-old teeth has yielded complete mitochondrial genomes for six people.

Calcified dental plaque, or calculus, is often preserved on ancient teeth, and studies have identified human and bacterial proteins in the build-up. A team led by Christina Warinner at the University of Oklahoma in Norman sequenced DNA in the calculus on 700-year-old remains from a cemetery in Illinois. The samples contained enough DNA to reconstruct full mitochondrial genomes.

The calculus can be useful when analysing remains that are considered to be sacred and that cannot be sampled using destructive methods, the authors note.

Am. J. Phys. Anthropol. http://doi.org/bdnb (2016)