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7. Some readers may regard the evolution of dinosaurs into birds and vice versa as science fictions or fairy tales. The experiments in the following two articles show the possibility of turning chickens into dinosaurs.|
Following are excerpts from Zoe Brennan's 13 June 2008 article headlined "Jurassic Park comes true: How scientists are bringing dinosaurs back to life with the help of the humble chicken" at the dailymaildotcodotuk website.
.....It is generally accepted by palaeontologists that birds are descended from a class of theropod dinosaurs called raptors.
‘If we want to see a dinosaur in our lifetime, we need to start with a bird and work backwards,’ says Horner (professor of palaeontology at Montana State University).
‘As long as birds exist, we have the ability to reach back to dinosaurs.’
In the 1990s, scientists discovered dinosaurs in China buried in a fine ash.
They were preserved in remarkable detail and bird-like features, including claws and feathers, were recognisable.
Horner believes that a modern bird’s DNA contains a genetic memory that could be ‘switched on’ again, resurrecting long-dormant dinosaur traits.
To make such a creature, he would start with the genome (the whole hereditary information encoded in the DNA) of an emu.
‘Emus have all the features we need in order to make a Velociraptor-sized dinosaur,’ he says.
‘If I were to make a dinosaur, that is where I’d start.’
Far-fetched as this sounds, his work is supported by other leading academics.
Sean Carroll, a geneticist at the University of Wisconsin, says: ‘The inventory of genes in a bird would be very similar to the inventory of genes in a dinosaur.
‘It is differences in the decision-making that takes during development that make the difference between a chicken and a tyrannosaurus.’
Hans Larsson, a palaeontologist at McGill University in Canada, conducted an experiment in November 2007 into the evolution from dinosaurs’ long tails into birds’ short tails more than 150 million years ago.
Looking at a two-day-old chicken embryo, he made an unexpected discovery.
Expecting to see between four and eight vertebrae present in the developing spine, his microscope instead picked out 16 vertebrae — effectively a reptilian tail.
As the embryo developed, the ‘tail’ became shorter and shorter, until the young bird hatched with only five vertebrae.
Larsson says of the significance of the find: ‘For about 150 million years, this kind of a tail has never existed in birds.
'But they have always carried it deep inside their embryology.’
So, the blueprint for a dinosaur remained locked inside the modern-day bird.
Larsson decided to move from theory to reality.
He wanted to see if he could make a chicken grow a dinosaur’s tail, turning the clock back millions of years.
Manipulating the genetic make-up, he was able to extend the tail by a further three vertebrae.
Larsson had pinpointed a method for turning on dormant dinosaur genes.
If birds retained a dormant tail imprint, did they still retain a memory of dinosaur teeth?
In 2005, Matt Harris and John Fallon, developmental biologists at the University of Wisconsin, noticed something strange while researching mutant chickens.
Harris says: ‘Looking at an embryonic 14-day-old head, I came across the beak and these structures that were not supposed to be there.’
Could they really be teeth? Peeling away the beak in this tiny, mutant bird, the academics revealed sabreshaped formations almost identical to embryonic alligator teeth.
Next, Harris and Fallon attempted to trigger the formation of teeth in a normal chicken, by injecting the embryo with a virus designed to ‘turn on’ the relevant gene.
It was a long shot.
‘Making a tooth is complex,’ says Harris. ‘So the idea of turning on one gene that might be able to do this in an animal that hasn’t made teeth in over 70 million years, was somewhat of a stretch.’
Examining the growing embryo two weeks later, he called colleagues to look at what had happened.
‘You could see very clearly paired structures on the lower jaw.
'And so, a normal chicken can actually grow teeth.’
This was unexpected. Furthermore, the teeth had the same curved shape as dinosaur fangs.
Following this, Harris and Fallon began to find other dinosaur traits in the DNA of birds, such as scales.
They looked at an ancient Chinese breed of chicken called a Silkie.
It has primitive plumage similar to that believed to grow on some dinosaurs.
By activating a dormant gene, Harris and Fallon attempted to ‘trick’ the chicken’s leg into growing feathers instead of scales.
It worked — they had uncovered the genetic changes that had taken place as the dinosaur evolved into a bird.
Meanwhile, in Canada, Larsson had found that the three-fingered dinosaur claw structure remains hidden within a bird’s wing to this day.
‘The dinosaur fingers are adapted for grasping and snatching prey,’ he explains.
‘If we compare this to modern birds, we see the same structures in their wings but adapted for flight.’
With further research, he believes scientists should be able to transform a bird’s wing back into a dinosaur arm.
So, will it one day be possible to reverse evolution?
Mark Westhusin is a world-renowned expert in creating life forms from DNA.
Together with his colleague, Dewey Kramer, at Texas A&M University, he has cloned more species than researchers at any other laboratory, including a White-tailed deer and a Black Angus bull.
Westhusin explains that soon, the relevant DNA to turn back the clock could be manufactured and implanted into an emu egg, for instance, to trigger dormant genes.
‘We already have small artificial chromosomes that have been put into embryos and develop and divide and express their genes,’ he explains.
‘The technology is advancing so fast, in sequencing genes and in putting genes back together, and in manufacturing long stretches of DNA.’
Larsson now believes that in a hundred years or so, geneticists could retro-engineer animals that appear identical to Mesozoic dinosaurs.
‘Why can’t we take all the genetics, just change it around a little bit, and produce a Tyrannosaurus Rex, or something that looks like one?’ he asks.
‘I think that kind of scenario is quite possible. Maybe sooner than we think.’
Fallon agrees, saying: ‘As we learn more, we’ll be able to do it.
'The genetic knowledge is in the bird.’
For his part, Horner imagines creating the first example.
‘I have to admit that I’ve certainly imagined walking up on a stage to give a talk, and having a little dino chicken walk up behind me,’ he says.
‘That would be kind of cool.
‘There is now nothing to stop us bringing back dinosaurs but ourselves.
'People who don’t believe it don’t know much about evolution.’
Pausing for a second, he adds: ‘Whether it is a good idea or not is another question...’ (End excerpts)