The key to the resurrection of extinct species lies in DNA and cloning. A complete genome can be obtained from genome sequences, and using technology not available at present, the DNA with the correct amount of chromosomes could be recreated using DNA building blocks. The chromosomes would then be packaged into an artificial nucleus and inserted into the egg of a surrogate species. Mammal embryos of the extinct species would hten be omplanted into the womb of a surrogate mother. This is but one way to revive a species.
Jack Horner believes there is an alternate way to revive the famous dinosaurs other than obtaining their DNA. From the field of evolutionary developmental biology, Horner wants to change the embryological development of the living descendants of the dinosaurs, chickens. Chicken embryos start to grow tails, like that of the Archaeopteryx, the earliest known bird, but then stops and is converted into a pygostyle. A pygostyle is a bone that holds the tail feathers for birds. When studying this process, scientists discovered that two sets of genes control the growth of the tail, one to grow the bones and another to control the transformation of the tail bones into other structures.
Horner proposes to alter the latter set of gene so that the chicken, instead of growing a pygostyle, would instead grow the long tail of the Archaeopteryx. Hans Larsson then thought that by splicing the the tail of a young embryo onto an older embryo, the older embryo would continue growing a tail, as opposed to forming the pygostyle. Although this experimentation did not succeed, it is worthwhile to look further into Horner's theory.
