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An
insect (the dark spot) trapped inside a chunk of amber
. (Copyright Lee Krytek 1996)
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How to Make a Dinosaur
In the book Jurassic Park (later turned into
a movie of the same name) author Michael Crichton describes a
formula to bring dinosaurs, extinct
for 65 million years, back to life:
STEP 1)Find a piece of amber with a blood
sucking insect from the dinosaur era trapped in it.
STEP 2)Extract the blood that insect sucked
from a dinosaur.
STEP 3)Use the dinosaur's genetic code
(DNA) found in the blood cells as blueprints for another dinosaur.
If pieces of the DNA are missing, fill in the gaps with frog
DNA.
STEP 4)Use these blue prints to create
a dinosaur egg.
STEP 5)Hatch the dinosaur in an incubator.
STEP 6)Raise the dinosaur to full size.
STEP 7)Enjoy!
Could we really use this formula to recreate dinosaurs?
If we can't today, could we reasonably expect our technology
to get good enough that we could do it in the future?
Let's look at step one. The idea of getting dinosaur
DNA from biting insects trapped in amber originated with George
O. Poinar in the 1980's. Amber is fossilized
tree sap. Usually it is clear with a yellowish tint. Sometimes
insects are trapped in the tree sap before it hardens. Some
amber dates from the Mesozoic Era when the dinosaurs lived and
it is not impossible insects, carrying dinosaur blood, might
be trapped in amber. Step one looks okay if we are willing to
spend the time and money to search for the right pieces of amber.
Amber is extremely useful for ancient DNA research.
In most fossilized bones the actual organic material has been
replaced by minerals. Amber preserves the soft tissue of an
animal, though, for vast amounts of time.
Step two is to remove the dinosaur DNA from the
insect. DNA, often called the blueprint of life, is found in
every cell in a living body. It is not unreasonable that we
might be able to extract some dino DNA from the blood cells
we recover. After that, though, we run into trouble. Scientists
have already extracted DNA fragments from an extinct weevil
that was trapped in amber some 120 to 135 million years ago.
Note that it was only a fragment of DNA of the weevil
(less than one millionth of the entire sequence), and not
the blood of something it bit.
A full set of DNA does carry the blue prints of
the creature of which it is a part of. However, this code is
made up of billions of individual "base pairs" (like letters
in an alphabet) and the order of these are very important to
the code. DNA is relatively fragile and breaks down over time.
The DNA we are likely to recover from the stomach of an insect
will have disintegrated into tiny pieces and most of it will
be missing. Unfortunately we cannot just replace the missing
section with frog DNA. If we did that we would wind up with
frog DNA with a few tiny dinosaur sections rather than dino
DNA with a few frog sections.
It's going to be difficult for scientists to even
be sure they have a fragment of dino DNA and not a part of the
insect or contamination from something under the researchers
fingernails. Remember nobody has ever seen dinosaur DNA before
so we they can only identify it by comparing and contrasting
it to DNA from animals alive today.
If we were going to fill in missing section of
dinosaur DNA it would be more logical to borrow it from birds
since they seem to be the closest living creatures to a dinosaur.
When we reach Step Three things really get difficult.
DNA is often likened to a software program on a computer because
it contains instructions on how to build a living creature.
(Whereas the instructions in a computer program might tell the
machine how to do your taxes.) To do something on a computer,
though, you need not only the software, but the hardware (the
computer itself) to run it. In the same way, we are missing
the "hardware" needed to execute the DNA. This would normally
be a mommy dinosaur that produces an egg with the DNA in it.
Unfortunately not any old chicken egg will do it. We need a
dinosaur egg. Probably one from the same species we are trying
to duplicate. Could we alter something like an Ostrich egg for
this purpose? Maybe, but today we don't know how to do it, or
what kind of changes are needed.
Assuming we do find some way past this obstacle,
what's next? Hatching the dinosaur in an incubator. This we
have plenty of experience with. If the eggs are good we can
probably get them to hatch.
Now we have to raise our baby dinosaurs to adulthood.
Our experience with raising other species will help. California
condors in captivity were raised using puppets to play the parts
of the parents. This way they did not get too comfortable with
human beings and the transition to living on their own in nature
was made easier. The logistics of providing an eighty foot long
Apatasaurs puppet for this purpose might be difficult, but not
insurmountable.
Still, we'd have to be concerned about the health
of our dinosaur. What do we feed it? Many of the plants it ate
back in the Mesozoic will be extinct themselves. What kind of
new germs have developed in the past 65 million years to which
our dinosaur has no resistance? What kind of medicine can we
give our dinosaur if it gets sick? With no past history of dinosaur
behavior to work from it will be hard to tell if our dinosaur
is acting "normal" or not.
Even if we never are able to build a dinosaur
from fossilized DNA scientists can still learn a lot about these
creatures, and life in general by studying sections of ancient
DNA to see how it has changed though the ages.
And who knows? If we can get past all these obstacles
perhaps we can someday build a dinosaur. Meanwhile, until we
do, we'll have to be satisfied with watching them in the movies.
Amber may turn out not to be the only potential
source of dinosaur DNA. While most fossilized
bones no longer contain any biological material there maybe
rare cases where organic material has survived the fossilization
process. Scott Woodward, of Brigham Young University,
has reported finding DNA in bones recovered from an underground
coal mine.
Woodward knew that carcasses found in peat bogs
were often well preserved for long periods of time. He also
knew that ancient bogs became modern coal veins. Getting a hold
of some bone fragments found in a coal mine Woodward decided
to look for DNA.
As Woodward had hoped the bone wasn't completely
fossilized and portions were "waxy, like hard soap." Microscopic
examination of the bone showed that the cell structures were
still preserved, so he began to look for DNA.
One gene segment, 174 base pair long, was found.
It didn't look like the same gene from any living animal, a
strong indication it wasn't the result of laboratory contamination.
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A fragment
of dinosaur bone.
(Copyright Lee Krystek
1996)
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Though Woodward cannot say for sure that the bone
fragments found in coal were from a particular dinosaur, he
does know that whatever animal it was large and lived some 80
million years ago during the Certaceous. A dinosaur seems like
a good candidate.
If Woodward can show he actually has dinosaur
DNA his technique may be extremely useful for learning more
about extinct creatures. Unlike with insects in amber, getting
DNA right from dinosaur bone would allow a specific DNA sequences
to be associated with specific dinosaur species.
Paleontologist Jack Horner and graduate
student Mary Schwietzer had already been trying to isolateTyrannosaurus
Rex DNA from bones even before Woodward started his
work.
While getting DNA from dinosaurs is difficult,
recovering it from more recently extinct species may be fairly
easy. Hendrik Polinar of the University of Munich has managed
to identify a Giant Sloth from the DNA
in the creature's softball sized droppings. The dung was left
in a cave near Las Vegas some 20,000 years ago. As time when
on the DNA became "caramelized" as the protein and sugar molecules
became intertwinded. This protected the DNA from decay. Polinar
was able to later split the bonds and read the genetic sequences.
Dispite the preservation much of the DNA material was still
lost, though, and it seems unlikely that this process could
be used to create a Giant Sloth for a "Jurassic Park."
Next
Stop on Dinosaur Safari
Book:
"The Science of Jurassic Park"
Copyright Lee Krystek
1996, 1998. All Rights Reserved.