The powerful Habsburg dynasty ruled Spain and its empire from 1516 to 1700 but when King Charles II died in 1700 without any children from his two marriages, the male line died out and the French Bourbon dynasty came to power in Spain.
Using genealogical information for Charles II and 3,000 of his relatives and ancestors across 16 generations, Gonzalo Alvarez and colleagues at the University of Santiago de Compostela, Spain have provided genetic evidence to support the historical evidence that the high frequency of inbreeding (mating between closely related individuals) within the dynasty was a major cause for the extinction of its male line.
You can read more at http://www.sciencedaily.com/releases/2009/04/090415075148.htm.
My thanks to Dave McDonald for telling me about this article.
