DNA, teeth and disease

A tooth is rot-resistant and even resists to a certain degree of carbonization. Its DNA constitutes a valuable element in investigations, even centuries after someone dies. For instance, it gives information about a direct line of descent, an identification, a poisoning or chronobiology, since it has been proved that a Neanderthal lies dormant in every man. Surprisingly that dental DNA can reveal a disease that would have affected someone centuries before. To that extent researchers managed to sharpen their knowledge of a disease - how it emerged, how it developed, how it spread. Then it was ascertained that 30 percent of the soldiers of the Great Army who were retreating during the Russian Campaign (1812) had died from the typhus spread by lice, and not in fighting. Moreover the way the Great Black Plague proliferated in the Middle Ages (1348-1352) got better understood. It has also been found out that the leprosy virus has never mutated for 1000 years, which gives hope to the prospect of a vaccine made on a centuries-old gene basis. All that from a simple tooth...