Cloning the Thylacine: Fact or Fantasy?

Scientists have recently succeeded in cloning sheep, pigs and mice from single living cells. Some scientists now claim that it will be possible to resurrect extinct animals using similar technology.

Can the Thylacine, an extinct Australian marsupial, be brought back to life using ancient DNA extracted from a joey (Thylacine pup) preserved in ethanol since 1866, as recently claimed?

To resurrect the Thylacine scientists would need to:

1. Extract intact DNA from the cells of the Thylacine joey,
2. Place the DNA in an artificial cell membrane,
3. Transfer the enclosed DNA into the live cell of some other animal, and
4. Grow this cell in the womb of a surrogate host.

This is unlikely to succeed because the DNA of the Thylacine will not be preserved intact. As soon as an animal dies biological molecules know as enzymes begin to break down its cells and the DNA contained within them. Not only would the DNA recovered from the Thylacine joey be fragmented, it would represent only a tiny portion of the animals genome (the entire genetic code of the animal).

Another problem is the absence of a suitable host in which to clone the Thylacine. The closest living relatives of the Thylacine are the dasyurid marsupials (e.g. Tasmanian devil) and perhaps the numbat. Not only are these animals considerably smaller than the Thylacine, they are not even that closely related. At least 25 million years of evolution separates these groups!

Imagine trying to clone a human using a small monkey as a host and you can begin to see what the problems are. Will the reproductive system of the host be large enough to accommodate the growing Thylacine embryo? Will the gestation period be the right length? Will the newly born Thylacine be able to suckle the milk of its distantly related host?

These are just a few of the problems but they are enough to illustrate that cloning the Thylacine quite firmly in the realm of fantasy.

See also: Prehistoric Life: Can dinosaurs be re-created from ancient DNA?