India, June 7 -- F or 150 million years, a group of species derided by anglers as "trash fish" (because they're too bony to eat, and eat fish that are delicious) have stayed precisely the same, a rare consistency not seen even in sharks. Across all that time, the gar, which looks like a cross between a fish and an alligator and is shaped somewhat like a torpedo, has seen DNA and RNA change up to three orders of magnitude more slowly than any other major group of vertebrates, including living fossils such as the coelacanth. Its DNA is so strong, in fact, that it can still procreate by hybridising, or fertilising the eggs of other gar species. Molecular mutations are so rare that studies indicate they amount to only 0.00009 mutations per mill...