Ever since “Jurassic Park,” people have wondered if it might one day be possible to clone a living, breathing T-Rex from an ancient fragment of DNA. This is one of those ideas that sounds eminently sane in principle—after all, biologists have managed to clone an entire sheep, and sheep are much farther up the evolutionary ladder than dinosaurs—but there are some huge hurdles that will probably keep dinosaur theme parks in the realm of science fiction.
First—and easiest to surmount—is the problem of finding intact dinosaur DNA. Although this hasn’t quite happened yet, and many scientists doubt it ever will, there was a time when millions of dinosaurs roamed the earth—so somewhere, somehow, there may be an iguanodon egg preserved perfectly in an improbably gigantic piece of amber.
After that, the hurdles get bigger. Since it’s hugely improbable that we’ll ever find a single, undegraded cell carrying the complete dinosaur genome, scientists will likely have to piece together many separate strands of DNA, from different sources—and without knowing the complete, exact sequence of any one dinosaur species’ DNA, the odds of creating a fully functioning organism are extremely slim (most likely, the embryo would self-destruct very early on in the development process).
Then, of course, there’s the problem of gestation. Dolly the Sheep didn’t grow in a test tube—she was implanted as an embryo into the womb of an ordinary ewe. Yes, dinosaurs hatch from eggs rather than growing in utero, but somewhere along the line there still has to be a surrogate mom, and without any dinosaurs around that’s a bit of a problem. Since it has now been pretty much established that birds are directly descended from dinosaurs, some folks have considered recruiting ostriches for this purpose (in the same way scientists have discussed cloning woolly mammoths by way of modern elephants). Feel free to picture the difficulties yourself.