GRANTS PASS, Ore. — Fossilized bacteria found inside a tick encased in 15 million-year-old amber indicates the bacteria that cause Lyme disease were likely around long before there were humans.

George Poinar Jr. bought the amber about 30 years ago in the Dominican Republic while researching the ancient origins of diseases spread by ticks and mosquitoes. Poinar is a professor emeritus of entomology at Oregon State University