An engaging example of genetic engineering, or synthetic biology, is creating living dinosaurs. Think Jurassic Park, the popular 1993 film. Imagine creating a living, breathing, Velociraptor or even a Neanderthal man.
Jurassic Park portrayed extracting dinosaur DNA from mosquitoes embedded for millions of years in amber, the transparent yellow and hardened tree sap. Scientists feel that while this approach might work, the chances of success are very small. One problem is that DNA can only survive for about 6.3 million years or so, and dinosaurs died out 65 million years ago. Another approach, which has more promise, is working backwards from birds. Reversing time, so to speak.
Paleontologists generally agree that birds descended from raptor dinosaurs. McGill University professor Hans Larsson and a former graduate student found that carnivorous dinosaur limb lengths showed a relatively stable scaling relationship with body size. The limb scaling changed when fore- and hind limbs dramatically decoupled from body size, which allowed birds to evolve from the dinosaurs. The hind legs shortened from monster thighs to very short and stick-like. The front legs evolved into wings. The long, heavy tails became residuals and were replaced by fans of feathers. The new bird species, of course, also had to develop hollow bones, small body sizes and high metabolic rates. Some dinosaurs already had feathers.
Their bigger discovery, however, was that the dinosaurs’ ancestral DNA is still present in the birds. In 2007, Larsson was examining a chicken embryo and with his microscope could find 16 vertebrae instead of the expected four to eight vertebrae—the bird had a residual reptilian tail. Larsson said, “For about 150 million years, this kind of tail has never existed in birds, but they have always carried it deep in their embryology.” Then he decided to see what would happen by manipulating the genetic make-up of the tail. He extended it by another three vertebrae. He had demonstrated a method for turning on dormant dinosaur genes.
A corroborating find was by Matt Harris and John Fallow at the University of Wisconsin in 2005. They found signs of undeveloped teeth in mutant chickens. Harris and Fallow turned-on the “teeth gene” using a triggering virus and their chicken grew the curved teeth like those of a dinosaur. (Can we still say “Scarce as hen’s teeth”?) They also programmed the chickens to grow feathers on their legs instead of scales. The dinosaurs’ genome, which was mutated to become a bird, could be reversed so a bird could become a dinosaur.
Larsson believes that in a hundred years or sooner geneticists will be able to retro-engineer dinosaurs including the gigantic Tyrannosaurus Rex. All the genetic coding is in the bird.
This will be discussed in more detail in my forthcoming book, Winter of the Genomes.