Scientists still have to be careful about which tools they use to answer a particular question about a particular species, said Steve Gniadek, wildlife biologist at Glacier National Park. And even with high-tech techniques, he admits, there are still a handful of assumptions that must be made in any study, assumptions that might taint pure results. Those guys work with beans that can be easily counted. When you try to count animals, even with DNA, you ratchet up the number of variables quite a bit. And the older the DNA, the greater the number of variables.
Genetic markers deteriorate with time, and become contaminated by the DNA of other species.
That often makes studying very old samples nearly impossible. And studying modern samples has its own set of problems. If you want to know how human disturbance has changed the adaptive genetics of grizzly bears, for instance, you need to track several generations. McKelvey hopes the answer to that dilemma can be found by studying the viral community that lives inside the bears. A virus might reproduce every 20 minutes, he said, making it a perfect sample by which to measure adaptive genetic change.