As we are on the track to lose species at a mass-extinction pace, researchers are trying to clone them back to existence. Researchers in Russia and South Korea are trying to recover genetic material from a frozen woolly mammoth carcass and repopulate a "Pleistocene Park" with cloned herds of the currently extinct species. However, evolutionary biologist Beth Shapiro of the University of California at Santa Cruz said, "It's not possible to bring an extinct species back to life. The main reason for that is, once an animal is extinct, there are no longer living cells." Instead of actually cloning, researchers are aiming to insert snippets of specially designed DNA coding into a species' genome. Theoretically, it might be possible to add genetic traits from the extinct passenger pigeon's reconstructed genome to a closely related species.