(banging head on desk)
The writer was profiling a book, “Return of the Black Death: The World’s Greatest Serial Killer” by Scott and Duncan. I’m sure there’s some serious evidence in their 318 page book.
Well, it appears to be a slam dunk. :)
At the time that the book was written (2005), there hadn’t been a lot of good research done on genetic material from the mass graves from the black death. In 2010, a very detailed study came to light.
Since then, there have been additional studies. For example, see Haensch S, Bianucci R, Signoli M, Rajerison M, Schultz M, Kacki S, Vermunt M, Weston DA, Hurst D, Achtman M, Carniel E, Bramanti B (2010). “Distinct Clones of Yersinia pestis Caused the Black Death”. In Besansky, Nora J. PLoS Pathogens 6 (10): e1001134. Try
http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1001134
(or http://www.ncbi.nlm.nih.gov/pubmed/20949072 [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2951374/]).
They studied bodies from plague pits in multiple areas, as well as controls, and found the Y. pestis indications in plague-pit samples at multiple locations. As the authors state:
“In summary, two independent methods demonstrate that humans buried in mass graves that were historically and contextually associated with the Black Death and its resurgences, were consistently infected by Y. pestis in southern, central and northern Europe. Thus, the second pandemic was probably caused in large part by Y. pestis.”