Smithsonian.com

Seeing a hadrosaur alive would be a fantastic sight. Or any non-avian dinosaur, for that matter. As lovely as today’s avian dinosaurs are, it’s their distant, extinct cousins that fire my imagination. Sadly, despite the speculations of theoretical physicist Michio Kaku, I don’t think my dinosaur dreams are going to come true.

In a Big Think video posted last week, Kaku rhapsodized about the possibility of resurrecting extinct species through genetic techniques. I’m not as optimistic as he is, especially since Kaku glosses over some essential steps in his confused editorial.

Kaku spends most of the video talking about Neanderthals and woolly mammoths. These species went extinct so recently that, in some cases, researchers can extract DNA from their remains and go about reconstructing their genomes. Pretty cool science. Whether I’ll ever be able to cuddle a fuzzy baby woolly mammoth is another matter. (I’ve heard promises ever since I was a child. I’m still waiting.) But non-avian dinosaurs obviously present a different problem. They went extinct about 66 million years ago, and, given the circumstances required for genetic preservation, there’s no hope of ever obtaining Mesozoic dinosaur DNA.

But, Kaku says, “we have soft tissue from the dinosaurs.” He makes it sound as if dinosaur skeletons are saturated with bits of prehistoric flesh. “If you take a hadrosaur and crack open the thigh bones, bingo,” he says, “You find soft tissue right there in the bone marrow.”

Kaku’s going far afield from what science has actually revealed. Since 2007, paleontologists and molecular biologists have been tussling over the possibility that some non-avian dinosaur fossils might preserved the degraded remnants of soft tissue structures such as blood vessels. A Tyrannosaurus femur kicked off the debate, which has since extended to the hadrosaur Brachylophosaurus, as well.

Even though researchers Mary Schweitzer, John Asara and colleagues have hypothesized that they’ve detected preserved proteins from remnants of dinosaur soft tissues, their results have been heavily criticized. The supposed dinosaur leftovers may be microfossils created by bacterial biofilms that broke down the creature’s bodies, and the protein analysis–which placed the supposed T. rex protein close to bird protein–might have suffered from contamination. As yet, there’s no definitive proof that non-avian dinosaur soft tissues or proteins have actually been recovered, and the debate is set to go on for years to come. Contrary to what Kaku says, you can’t simply break open a dinosaur skeleton and start scooping out marrow.

Not that preserved protein would bring us closer to resurrecting Tyrannosaurus or Brachylophosaurus, anyway. The biomolecules could tell us a bit about dinosaur biology, and possibly become another way to test evolutionary relationships, but we’d still lack dinosaur DNA. And even if we could reconstruct a dinosaur’s genome, that doesn’t mean that we could easily clone one. Much like Michael Crichton before him, Kaku skips over an essential and complicated step–the development of the embryo inside the mother. How do you go from a genetic map to a viable embryo? And how can we account for interactions between the embryo and the surrogate mother–a member of a different, living species–that could influence the experimental animal’s development?

Studying the genetics and biomolecular makeup of prehistoric organisms is a fascinating area of research. And even though the dinosaur protein issue remains contentious, the debate has the potential to refine a new way to look at dinosaurs. That’s where the real value of this science is. Non-avian dinosaurs are long gone, and I don’t believe that we’ll ever be able to bring them back to life. But the more we understand about their biology, the better we can reconstruct dinosaurs in our scientific imagination.

Among living dinosaurs, the cassowary is one of the most fantastic. Photo by Paul IJsendoorn, from Wikipedia.

One of the reasons Jurassic Park was so successful–as a novel and a blockbuster film–is that it presented a plausible way to bring dinosaurs back to life. The idea that viable dinosaur DNA might be retrieved from bloodsucking prehistoric insects seemed like a project that could actually succeed. Even though the actual methodology is hopelessly flawed and would never work, the premise was science-ish enough to let us suspend our disbelief and revel in the return of the dinosaurs.

Nevertheless, Jurassic Park brought up the tantalizing possibility that scientists might one day resurrect a Brachiosaurus, Velociraptor or Triceratops. And every once in a while, rumors arise about someone who might just give the project a try. According to the latest round of internet gossip, Australian billionaire Clive Palmer is hoping to clone a dinosaur for an exotic vacation retreat. Palmer has since denied the rumors, but, for a moment, let’s run with the assumption that someone is going to pour millions of dollars into a dinosaur cloning project. Would it actually work?

As Rob Desalle and David Lindley pointed out in The Science of Jurassic Park and the Lost World, there were a lot of steps that Michael Crichton glossed over in his dinosaur cloning regime. The novelist never explained how scientists overcame issues of genetic contamination, figured out what a complete dinosaur genome should look like and, most important of all, figured out how to actually translate all that DNA into a viable dinosaur embryo. It’s not simply a matter of accumulating DNA pieces until scientists have mapped every gene. A creature’s genetics must be read and interpreted within a biological system that will create an actual living organism. There are innumerable hurdles to any speculative dinosaur cloning project, starting with the effort to actually obtain unaltered dinosaur DNA–something that has never been done, and may never be.

If Palmer, or anyone else, wants to create a dinosaur park, it would be far easier to set up a reserve for living dinosaurs. The cassowary–a flightless, helmeted bird–is sufficiently prehistoric-looking to make it a draw for visitors. True, it’s not a Velociraptor, but a cassowary is most certainly a dinosaur that does pack a mean kick. There are plenty of living dinosaurs that could use a hand through conservation programs, so perhaps it would be better to try to save some avian dinosaurs rather than bring their non-avian cousins back from the dead.

How to Build a Dinosaur by Jack Horner and James Gorman

When the film adaptation of the science fiction novel Jurassic Park premiered in the summer of 1993, scientists and the public alike wondered if it was possible to bring dinosaurs back from the dead. It was a tantalizing prospect, but the general consensus was that even if dinosaur DNA could be recovered, there were simply too many obstacles. Cloning a non-avian dinosaur appeared to be all but impossible.

Yet perhaps there was another way. In the 1993 NOVA program “The Real Jurassic Park,” paleontologist Robert Bakker suggested that since birds were living dinosaurs, they still carried the genetic code for the formation of teeth, a long tail, and other “dinosaurian” features. If these genetic “switches” could be turned back on then scientists could, to a limited extent, reverse-engineer a dinosaur. Sixteen years later paleontologist Jack Horner has further developed this hypothesis and, with science writer James Gorman, explained it in his new book How to Build a Dinosaur.

When I hear the word “paleontologist” I almost always think of a flannel-clad scientist prying an ancient monster from the rock of a dusty and barren landscape. To some extent this association is accurate, but during the past few decades the discipline of paleontology has diversified to include researchers who specialize in microbiology, development, and genetics. From the structure of dinosaur bone to the controversy over potential Tyrannosaurus rex soft tissue, the first half of the book focuses on how paleontology has been married to laboratory biology. While readers may be itching to get to Horner’s recipe for a dinosaur, this section is important. It summarizes the emergence of new areas of study within paleontology and confirms that it is unlikely that we will ever clone a dinosaur from preserved tissue. Dinosaurs, as they were from about 230 to 65 million years ago, are lost forever. Only bones and other rare traces of their existence remain.

This does not seem like a promising start for a book that claiming to explain how to build a dinosaur, but once the changing nature of paleontology is established, Horner & Gorman set off on another route. The science of evolutionary developmental biology, or evo-devo for short, can provide significant clues about major evolutionary changes. This is because evolution is constantly adapting existing structures to new functions. During the evolution of birds, for instance, dinosaurs did not lose their arms only to evolve wings from nothing. Instead the dinosaur forelimb, already feather-clad, was modified for flight.

It is also true that genes, particularly regulatory genes that organize the formation of the body during development, can be preserved and put to new functions just as parts of skeletal anatomy can. This means that by studying the embryological development of living birds, scientists can find clues as to how the bodies of some dinosaurs were formed. By tweaking the development of a chicken embryo they might be able to create a creature with a long tail, clawed hands, and teeth, just as Bakker suggested in 1993. The precise details of how this could be done are still largely unknown, Horner has no “recipe” to share, but the hypothesis that it could be done has merit.

(Wired magazine has an interview with Horner in which he proposes that by switching certain genes on or off during the development of a chicken, you could create something that looked more like Velociraptor and less like something destined to be made into deep fried nuggets.)

If these experiment were successful, the resulting creature would not be a true dinosaur; it would simply be a genetically manipulated chicken that would appear dinosaur-like. It would mostly be informative about the small maniraptoran dinosaurs from which birds evolved and would be less informative for the sauropods and the vast array of ornithischian dinosaurs (hadrosaurs, stegosaurs, ceratopsians, etc.). Horner & Gorman readily recognize this, and it is just as well. The goal of the project is not to create a living dinosaur but to understand how evolution works. If a creature could be created that revealed how the genetic code for ancient characteristics has been retained and re-activated, the animal would be a striking illustration of evolution. More than that, by bringing these traits out paleontologists may be able to understand the details of how birds evolved from theropod dinosaurs.

The importance of How to Build a Dinosaur does not lie in Horner’s wish to create a dinochicken. That makes up only a small part of the book. Instead the slim volume indicates how paleontology is becoming more of an interdisciplinary science where studies of development and genetics are just as important as fossilized bones. It remains to be seen whether Horner will be able to open a “Jurassic Barnyard”, but that is not the point. The bodies of living things hold records of the past just as the strata of the earth do, and when both lines of evidence are studied together scientists can finally begin to answer evolutionary questions that have puzzled researchers for decades.

Charles R. Knight's 1896 painting of Dryptosaurus. From Wikipedia.

When the film adaptation of Jurassic Park came out in 1993 the idea that scientists may one day be able to clone dinosaurs had everybody talking. It is still more science fiction than science fact (check out The Science of Jurassic Park and the Lost World), but suppose for a moment that there was some breakthrough that allowed scientists to bring back the dinosaurs. Which dinosaur would you want to see brought back to life?

I know it would be difficult for me to choose. There are just so many fascinating dinosaurs that I would love to see them all in the flesh. If I had to pick just one, though, I think I would vote for Dryptosaurus. It is not a particularly popular dinosaur but it was very significant in revolutionizing the image of dinosaurs in the late 19th century. Found in my home state of New Jersey in 1866, it was one of the first dinosaurs to confirm that some of them walked on two legs and had bird-like characteristics.

What did Dryptosaurus look like? It is hard to say. Enough of its skeleton has been found to determine that it was a tyrannosauroid and may have been similar to Eotyrannus from England, but it is still only known from bits and pieces. Many of the sites in which more Dryptosaurus fossils might be found have either been closed down or built over by suburban sprawl, too, so we may never get a more complete understanding of this dinosaur. That’s why I would love to see it restored.

How about you? If you could tell scientists to clone any dinosaur which one would you choose?