Lyme Bacterium's Possible Ancestor Found In Ancient Tick

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.”'"

Let me calm your fears.

[mmell]

The longer a bacterium or virus has been present on the planet, the more likely it is that animals will have inherited a natural defense mechanism to cope with it. That's not an absolute; our inherited resistance to specified pathogens might be 'forgotten' over the course of centuries or millenia, but those immunities are theorized to be the reason that pathogens also evolve. In effect, pathogens learn to live in us. We learn how to evict them. They learn how to sneak back in. We learn how to catch them and eject them.

Yes, I know it's not a very scientific or thorough explanation. If you accept the principals of the theory of evolution and the concept of genetic drift, it makes sense. In any event, I suspect the modern forms of this bacteria are more virulent than their primitive ancestors.