Taco Cowboy (5327) writes "A few ancient ticks, some 15-million to 20-million years old, trapped inside a piece of amber were bought by a researcher some 25 years ago, in the Dominican Republic. Upon examination, he found ancient spirochetes bacterium, a group of rotini-shaped bacteria responsible for many human diseases, in one of the ticks. Although Lyme disease did not exist back then, the spirochetes in the fossil tick probably contributed to the genetic diversity of the 12 or more species of Borrelia that cause Lyme and similar diseases today, says George Poinar. 'Parasites represent at least half of all modern animal species, and that distribution probably held true millions of years ago, too. “In a sense, this [finding] is not surprising since virtually every species on the planet is parasitized,” says Armand Kuris, a parasitologist at the University of California, Santa Barbara, who was not involved in the study. Evidence of those ancient parasite–host associations is difficult to come by, however. “In terms of finding any kind of physical documentation in the fossil record, that’s really rare — especially for a microbial pathogen,” Kuris says. “That’s what makes this paper just plain interesting.”'"