The current issue of Science has an article on the costs and benefits of de-extinction, i.e., using biotechnology to resurrect species. The article by Stanford University scholars Jacob Sherkow and Henry Greely note that extinct species might be brought back to life by means of back-breeding, cloning, or genetic engineering.
Back-breeding would use selective breeding of species closely related aim at producing the phenotype of the extinct species, e.g., the Tauros Project is working to revive the auroch. Cloning could be used if a sufficiently well-preserved nucleus from the tissue of an extinct species could be tranferred into the enucleated egg of a similar species and then implanted in a surrogate. So far this has only been attempted with the recently extinct Pyrenean ibex. A kid was born but died of lung malformations soon after.
Perhaps the more promising, though more technically difficult route toward de-extinction, would be to isolate DNA from preserved tissue of an extinct species and then sequence it, e.g., a wooly mammoth. Then that information could be used to alter the genetic sequences in a closely related species, e.g., an Indian elephant, resulting in a wooly mammoth.
The authors observe:
De-extinction is a particularly intriguing application of our increasing control over life. We think it will happen. The most interesting and important question is how humanity will deal with it.
They suggest that some might object to de-extinction on the grounds that the resurrected creatures might be exploited, vectors for pathogens, invasive, examples of "playing god," or lessen people's concerns about extinction. On the benefit side, the authors them as …
… falling into five categories: scientific knowledge, technological advancement, concrete environmental benefits, justice, and "wonder."
To my mind, those benefits clearly outweigh the rather insubstantial objections cited by the authors, especially the last one. As the authors write:
The last benefit might be called "wonder," or, more colloquially "coolness." This may be the biggest attraction, and possibly the biggest benefit, of de-extinction. It would surely be very cool to see a living wooly mammoth. And while this is rarely viewed as a substantial benefit, much of what we do as individuals—even many aspects of science—we do because it's "cool."
See below 1933 footage of the last Tasmanian Tiger.