revived when available technology allows it (a concept which has been termed "de-extinction"), using genetic material from such specimens. In 2003, the Pyrenean ibex (Capra pyrenaica pyrenaica, a subspecies of the Spanish ibex) was the first extinct animal to be cloned back to life; the clone lived for only seven minutes before dying of lung defects. A hindrance to cloning the passenger pigeon is the fact that the DNA of museum specimens has been contaminated and fragmented, due to exposure to heat and oxygen. American geneticist George M. Church has proposed that the passenger pigeon genome can be reconstructed by piecing together DNA fragments from different specimens. The next step would be to splice these genes into the stem cells of rock pigeons (or band-tailed pigeons), which would then be transformed into egg and sperm cells, and placed into the eggs of rock pigeons, resulting in rock pigeons bearing passenger pigeon sperm and eggs. The offspring of these would have passenger pigeon traits, and would be further bred to favor unique features of the extinct species. The general idea of re-creating extinct species has been criticized, since the large funds needed could be spent on conserving currently threatened species and habitats, and because conservation efforts might be viewed as less urgent. In the case of the passenger pigeon, since it was very social, it is unlikely that enough birds could be created for revival to be successful, and it is unclear whether there is enough appropriate habitat left for its reintroduction. Furthermore, the parent pigeons that would raise the cloned passenger pigeons would belong to a different species, with a different way of rearing young. Bibliography Notes References Cited texts External links Project Passenger Pigeon: Lessons from the Past for a Sustainable Future The Demise of the Passenger Pigeon (as broadcast on National Public Radio's Day to Day) 360 Degree View of Martha, the Last Passenger Pigeon (Smithsonian Institution) passenger pigeon Extinct animals of Canada Pleistocene first appearances Native birds of the Eastern United States Extinct birds of North America Extinct animals of the United States Species made extinct by human activities Bird extinctions since 1500 Game birds passenger pigeon 1914 in the environment passenger pigeon Articles containing video clips Species endangered by deforestation Species endangered by use as food