In 2011, a team led by McMaster University paleogeneticist Hendrik Poinar became the first to reconstruct a full genome for Black Death era Yersinia pestis.
This was not a full and complete genome drawn from a single bacterium inhabiting the body of a single victim. Instead, the genome was patched together from bits and pieces of DNA in remains taken from London's East Smithfield cemetery. The small chunks were lined up to create a whole, similar to the way you make a panoramic photo by combining a series of different shots. Hendrik Poinar calls it a "draft" of the genome, rather than a smooth, polished work of biology.
The draft tells us a couple of things. First, the Y. pestis of the Black Death era is related to modern Y. pestis. In fact, it's probably the ancestor of all the strains of Y. pestis that exist today. Second — and this is the weird part — there is really not much difference between the old Y. pestis and the new. It boils down to about 100 genetic changes, few of which seem to have given the bacteria enough of an evolutionary advantage that they spread widely through the population.
Genetically, Y. pestis has barely changed. Its infection profile in the real world, though, has changed massively. That suggests that at least some of those small alterations in the genome must have been extremely important. But which ones? And why? To answer those questions, you could reverse-engineer the evolution of Y. pestis in the lab. "We'd have an opportunity to test those changes, one at a time, and find out," Poinar said. "... If we could do it in a form or fashion that wouldn't terrify people."
So, who's going to join me in volunteering to be infected with ancient plague for Science? After all, with modern medical care, there's probably at least an 80% chance of survival. I like those odds!