Will We Ever Be Able to Clone Dinosaurs?

Image credit: 
Lost-World.Com

Jurassic Park turns 20 this year, and today, a 3D version of the film hits screens nationwide. We asked Brian Switek, a science writer specializing in evolution, paleontology, and natural history, to weigh in on the movie's basic premise—that dinosaurs are cloned using DNA taken from mosquitoes.

When I was a little dinosaur fan, all I wanted was a pet dinosaur. An Apatosaurus would have been choice—big enough to be impressive, but not especially likely to eat me. But that’s never going to happen. As much as I hate to say that science will never solve a particular question or problem, the barriers to a real life Jurassic Park are insurmountable.

Time is the critical factor. The last of the non-avian dinosaurs—the undeniably awesome ones that haunt museum halls and our dreams—died out 66 million years ago. That’s so distant from us that we can’t even really comprehend how long that is, and we lost whatever chance we might have had at cloning dinosaurs within a relatively short time following the end-Cretaceous mass extinction.

This is not the dinosaur goo you’re looking for…

You may have heard that paleontologist Mary Schweitzer and colleagues have extracted some soft tissue remnants from the Cretaceous dinosaurs Tyrannosaurus and the hadrosaur Brachylophosaurus. These claims have been controversial, but they cannot be discounted. Schweitzer and others have built a startling argument that in exceptional cases, fragments of original dinosaur protein may have survived to this day. But that’s not what we need to clone a dinosaur. The starting point of any dinosaur resurrection exercise is DNA. Unfortunately for paleo nerds such as myself, DNA has a relatively short half life. There’s virtually no chance of ever recovering dinosaur genetic material.

For years, researchers have known that DNA starts to break down almost immediately after an organism perishes. Even in exceptionally-preserved animals from more recent times—such as frozen woolly mammoths found in Arctic permafrost—the genetic material of the creatures has unraveled into fragments of what once was. But it was only late last year that University of Copenhagen palaeogeneticist Morten Allentoft and coauthors figured out what the rate of DNA degradation is.

The disintegration of “Mr. DNA”

By looking to bones of recently-extinct avian dinosaurs—specifically, the 8000- to 600-year-old bones of giant, flightless birds called moa that once strode over New Zealand—the geneticists calculated that DNA has a half-life of 521 years. That’s longer than researchers expected, but not nearly long enough to allow us to ever obtain Tyrannosaurus or Triceratops DNA (much less far more ancient dinosaurs such as Brachiosaurus and Dilophosaurus). Even under ideal conditions wherein bones would remain dry and chilled at a temperature of 23 degrees Fahrenheit or lower, the entirety of a creature’s genome would be obliterated within 6.8 million years, or about 59 million years short of the last non-avian dinosaurs.

It’s really as simple as that. No DNA, no revived Velociraptor. (I’m not entirely sure whether that’s a good or bad thing.) And the whole “dinosaur blood from amber” would not have worked, either.

Let’s assume for a second that the fossilized tree sap and insect within were exempt from biological reality and actually contained DNA. Drilling through the amber to get to the insect’s gut contents would be an exercise in contamination—mashing genetic material from the tree, insect, and dinosaur gunk together.

But for the sake of the movies, let’s stretch our suspension of disbelief a little bit further. Let’s say that through magic or other equally impossible methodology, scientists are able to extract dinosaur DNA from ancient bone or other source. That is just the very first step in getting anywhere near recreating a Spinosaurus.

Parasaurolophus Puzzle

Any ancient dinosaur DNA would have come in dribs and drabs, just as with Ice Age mammoths, Neanderthals, giant sloths, and sabercats that have yielded genetic tidbits. The trick is identifying those pieces and figuring out where they belonged in an animal’s complete genome. That requires a baseline acquired from a close relative—modern Asian elephants work for mammoths, and our own genome for Neanderthals. But living avian dinosaurs are so far removed from Pachycephalosaurus and kin that their utility in figuring out the arrangement of non-avian dinosaur genomes would be quite limited. And that’s to say nothing of the pseudogenes and non-functional parts of the genome. We haven’t even completely sequenced the genome of our own species—we’re still at about 99 percent of the functional part—so we’re quite far from fully reconstructing an extinct genome.

Jurassic Park recognized this difficulty. That’s why the fictional engineers of the book and film took the boneheaded move of mixing frog DNA with dinosaur genes to create complete animals. And I don’t say “boneheaded” because of the plot twist consequence of “unauthorized mating” among the dinosaurs. By the time Jurassic Park came out, paleontologists were confident that birds were a surviving lineage of dinosaurs—a fact beautifully supported by a slew of fuzzy, fluffy, feathery dinosaurs that started popping out of the fossil record in 1996. Patching Velociraptor with bird DNA would have made a lot more sense, especially given the fictional paleontologist Alan Grant’s virtual obsession with pointing out how bird-like Jurassic Park’s dinosaurs were.

A Raptor By Any Other Name

So a Velociraptor or Tyrannosaurus genome wouldn’t be a feat of resurrection, but reinvention. Even if it were possible to retrieve dinosaur DNA, we’d have to reverse engineer the dinosaur genomes according to our best possible estimates of their anatomy and behavior. More hurdles abound.

Creating a complete DNA profile doesn’t get you anywhere if those genetic cues can’t be translated into a viable embryo that is going to grow to term. Understandably, Michael Crichton and the film adaptations of his work totally glossed over this point, especially since researchers can’t clone birds. It’s easy enough to say “We’ll stick an artificial nucleus inside an ostrich egg and the rest will take care of itself,” but that ignores the essentially biological interactions that actually constitute a living, growing organism. Since birds have outsourced the growth of their offspring outside the body, there may not even be a way to successfully clone a bird, and so there would be no method by which we could bring dinosaurs back even if we had all the requisite raw materials. It’d be like assembling all the materials for a cake and turning on the oven, but having no clue about the cooking chemistry of how to achieve the desired, tasty result.

There will never be a real Jurassic Park. But I’m not especially sad about that. Our favorite dinosaurs may never come back to life in a literal sense, but paleontologists are finding ways to extract ever-more details about dinosaur lives from what remains of the creatures. Science fuels our speculation, allowing dinosaurs to still live in the place where fossil facts and imagination meet. We still have our dinosaur dreams.  

Brian Switek tried really hard not to be a killjoy in this post. So much for that. He enthuses about fossil finds on his National Geographic blog Laelaps, and in his books Written in Stone and My Beloved Brontosaurus, out this month. “Brontosaurus” was slain by science over a century ago, yet the great dinosaur’s ghost is still with us. In My Beloved Brontosaurus, Brian follows the legacy of the cherished sauropod to explore how science has changed dinosaurs over the past thirty years, and has transformed familiar Mesozoic species into creatures more wonderful than anything we could have imagined. He lives in Salt Lake City, Utah, to be closer to the petrified inspirations of his writing.

More from mental_floss...

April 5, 2013 - 9:30am
submit to reddit