These are the steps that could, theoretically, allow an Asian elephant to give birth to a hybrid woolly mammoth, which could eventually breed with other hybrids to produce an animal that closely resembles the extinct species. A number of scientific hurdles, described below, still need to be overcome to make this a reality.
1. Map the woolly mammoth genome. Some of this work has already been done – researchers at Penn State University mapped roughly 70 percent of the woolly mammoth genome in 2008 using hairs from mammoths preserved in Siberian permafrost.
2. Determine how/where the woolly mammoth genome is different from the Asian elephant's, and change those genes accordingly. The Asian elephant is the woolly mammoth's closest living relative, and should, therefore, have the most genes in common with it than any other living animal. Researchers are still in the process of mapping the complete Asian elephant genome.
3. Introduce the modified genome into Asian elephant germ cells, or the cells involved in sexual reproduction. Scientists still haven't determined how to do this for mammals. The process is, theoretically, more plausible for animals with eggs that develop externally to mothers, such as birds, than for mammals. Methods are still in the works, and may not ultimately work.
4. Artificially inseminate a surrogate Asian elephant with new germ cells.
5. Germ cells become incorporated into a growing embryo. Techniques will need to be developed to ensure that the mammoth germ cells populate the gonads in greater numbers than the host's own germ cells.
6. A hybrid that looks like an Asian elephant is born through a C-section. The first hybrids will look like their Asian elephant surrogate mothers, but will contain mammoth DNA that will become more increasingly prominent once hybrids breed with one another. A C-section would be used during birth to avoid complications.
7. When two of the hybrid animals mate, their offspring would look like woolly mammoths. In principle, this should work, though depending on which germ cells become fertilized, the result may just look like a hybrid mammoth-elephant. The end product will not be an exact replica of a woolly mammoth, but should bear a close resemblance.