Which Came First: the Dinosaur or the Egg?

One of the things that fascinated me most in my high school and university biology classes was study of vertebrate evolution, and specifically that sequence of photos in the textbooks showing various vertebrate embryos at different stages of development during gestation: at some point in the womb, human beings look a lot like lizards, and birds, and all sorts of other things that we used to be on our way to be primates and eventually homo sapiens.

Well, now this same principle is being considered by some scientists to create what you might call “chickenosaurus”. While not exactly Jurrasic Park, some evolutionary biologists are teaming with paleontologists in hopes of genetically altering a chicken embryo to express some of the dormant traits held over from the days when birds used to be dinosaurs.

It wouldn’t be a dinosaur, and while genetically chickenosaurus would still be a domestic chicken, it wouldn’t exactly be a chicken, either. It might look something like Archaeopteryx–the earliest and most primitive bird known–having arms with claws instead of wings, teeth, and a tail; what science calls “atavistic structures”. Chickenosaurus would be a sort of evolutionary throwback–certain genetic signaling switches would be turned off or on depending on what features we were trying to express.

The book How To Build A Dinosaur by Jack Horner and James Gorman came out last week and an excerpt of the book in the Globe and Mail can be found here.

I may have to pick up that book…

– S.


Which comes first? The dinosaur or the egg?
It may sound like a Jurassic Park sequel, but scientists at McGill and several U.S. universities are working toward hatching a live dinosaur from a regular chicken’s egg. In this excerpt from their book How To Build a Dinosaur, paleontologist Jack Horner and co-author James Gorman explore why we should take this leap.


From Saturday’s Globe and Mail

March 28, 2009 at [12:00] AM EDT

Among the potential benefits of causing a chicken embryo to develop dinosaurian characteristics is that this is a project that could capture the popular imagination. It could be a demonstration of evolution that would be felt at gut level by nonscientists who might be uninterested in the details of genomes and embryos.

Anything that brings home to the public the reality of evolution, and its place as the foundation idea of modern biology, is important. Anything that dispels the fog of confusion about science and religion would be enormously positive.

Hatching a dino-chicken would be shockingly vivid evidence of the reality of evolution – not a thought experiment but an Oprah-ready show-and-tell exhibit. The creature would be its own sound- and vision-bite. It certainly wouldn’t convince anybody who didn’t want to be convinced. But it would cause discussion and thought.

Creating a demonstration suitable for sound-bite television is not, however a reason to do scientific experiments. In order to get to the point where the question “How did you do that?” could be answered, we would have to learn a great deal. And we would tie molecular biology to macroevolution. We would zero in on a significant passage in vertebrate evolution, the transition from non-avian dinosaurs to birds, and pin it down to molecular changes in embryonic cells.
It may sound like a Jurassic Park sequel, but scientists at McGill and several U.S. universities are working toward hatching a live dinosaur from a regular chicken’s egg.
Enlarge Image

It may sound like a Jurassic Park sequel, but scientists at McGill and several U.S. universities are working toward hatching a live dinosaur from a regular chicken’s egg.

This is the heart of the promise of evolutionary developmental biology.

Vertebrate paleontology may seem to be so remote from the daily problems of the modern world that it exists apart from society. If I were to be harsh, I might ask, “What good is it?”

There is an aspect of vertebrate paleontology that is highly useful and of great importance to us as vertebrates. That vertebrate body plan is one we share with dinosaurs, chickens, and countless other creatures.

The result of this commonality of life, in this case in the specific fraternity of four-limbed vertebrates, is that lessons we learn about the growth of any tetrapod embryos may have significance for the growth of human embryos.

If we learn about the growth factors that signal the neural tube to continue developing, it’s possible that this knowledge could be useful in preventing birth defects.

In spina bifida, for instance, incomplete development of the spinal cord can leave an infant with painful and sometimes lethal birth defects.

In the 1980s researchers pinned down the importance of folic acid to the development of the spinal cord in human embryos. This discovery was made partly by gathering information about the diets of pregnant women and the incidence of spinal-cord birth defects like spina bifida, and partly with animal research. The simple remedy of adding folic acid to the diet of pregnant women now prevents countless cases of these defects.

Knowing that there are great potential benefits answers some questions about whether such research should be done. But there are others. Is it a morally justifiable act to play with life in order to go back in time? Is it cruel? Is it dangerous?

Experimentation of all sorts on chicken embryos is widely accepted and, I think, the correct assumption is that we are not causing the embryo pain. As to ultimately sacrificing the embryo, or a fully grown chicken, there are far greater injustices and indignities that billions of chickens face every day. Common sense would suggest that not allowing an egg to hatch, or humanely killing even a full-grown chicken, are actions that society recognizes as legitimate, given even the small return of a meal. The potential return is much greater here.

No one is ready to let an embryo experiment hatch yet. But when that point is reached, when the plan is to have a fully formed dinosaurlike chick hatch, then the experiment will come under review boards that deal with animal welfare. My sense is that providing a chicken with arms with claws instead of wings, with teeth, and with a tail, would not be cruel. In fact, if the atavistic structures grew improperly or were malformed in a way that would cause the animal pain, that in itself would mark a clear failure, since the whole point is to re-create functioning atavistic characteristics, not monstrosities.

There is a whole range of possible objections that have nothing to do with the health or life conditions of what we could probably call chickenosaurus. And that is fear for the environment, for interfering with the delicate ecological balance of the planet.

But if the embryo is not allowed to hatch, then it won’t be out in the environment at all. If it were allowed to hatch, and somehow escaped, the only problem would be the chickenosaur figuring out how to survive. It would not be a danger to the environment or to the billions of chickens in the world, because we would not be changing its genetic makeup. By manipulating growth signalling factors we would be switching genes on and off at different times during development, but not changing the genes themselves. Genetically, chickenosaurus would still be a domestic chicken. And if it were somehow to breed with a chicken, the result would only be more chickens.

I can say what interventions I would find reasonable, but I am not the one to decide. That is for society at large.

What I and other scientists can decide is whether or not to pursue knowledge that has the potential to teach us a great deal and to provide powerful tools that could be used for good purposes and bad.

My work is all about finding things out, about learning, and I operate on the principle that we should try to find out as much as we can about the way the world works.

I don’t stop and say, “Could this research find out something that might be misused, might cause more evil than good?”

I follow my nose to see what is interesting. When it comes to the question of how that knowledge is used, I am just another citizen.

Reprinted by arrangement with Dutton, a member of Penguin Group (USA) Inc., from How to Build a Dinosaur, by Jack Horner and James Gorman.

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