De-extinction

De-extinction, or resurrection biology, or species revivalism is the process of creating an organism, which is either a member of, or resembles an extinct species, or breeding population of such organisms.Cloning is the most widely proposed method, although selective breeding has also been proposed. Similar techniques have been applied to endangered species.

There is significant controversy over de-extinction. Critics assert that efforts would be better spent conserving existing species, that the habitat necessary for formerly extinct species to survive is too limited to warrant de-extinction, and that the evolutionary conservation benefits of these operations are questionable.

Cloning is one method discussed as an option for bringing extinct species back. Proponents include author Stewart Brand, and proposed species include the passenger pigeon and the woolly mammoth. De-extinction efforts are now underway to revive the passenger pigeon by extracting DNA fragments and taking skin samples from preserved specimens and, later, using band-tailed pigeons or rock pigeons as surrogate parents.

A team of Russian and South Korean scientists are, as of April 2013, in the planning stages of cloning a woolly mammoth using an Asian elephant as a surrogate mother. Large amounts of well-preserved mammoth tissue have been found in Siberia. If the process can be completed, there are plans to introduce the mammoths to , a wildlife reserve in Siberia. (Evolutionary biologist Beth Shapiro points out that "cloning" is a specific technique which cannot be accomplished without a living cell, none of which are available for mammoths, but suggests genome editing might be feasible.)

Although de-extinction efforts have not yet succeeded in producing viable offspring of a previously extinct species, the same process has been applied successfully to endangered species. The banteng is the second endangered species to be successfully cloned, and the first to survive for more than a week (the first was a gaur that died two days after being born). Scientists at Advanced Cell Technology in Worcester, Massachusetts, United States extracted DNA from banteng cells kept in the San Diego Zoo's "Frozen Zoo" facility, and transferred it into eggs from domestic cattle, a process called somatic cell nuclear transfer. Thirty hybrid embryos were created and sent to Trans Ova Genetics, which implanted the fertilized eggs in domestic cattle. Two were carried to term and delivered by Caesarian section. The first hybrid was born on April 1, 2003, and the second two days later. The second was euthanized, but the first survived and, as of September 2006, remained in good health at the San Diego Zoo.

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