Test Tube Dinosaurs? - London Student
19 Nov 2012 | News
and Features
Written by Helga Groll
Dinosaurs, the giant primeval beasts, have fascinated old and young for
generations. Michael Crichton and Steven Spielberg’s Jurassic Park has inspired
fantasies that we might one day see these prehistoric creatures in real life.
In the movie, scientists used dinosaur blood from the stomachs of fossilised
parasitic insects that were once sucking on T-rex and Co to extract DNA and
bring the fearsome reptiles back to life.
Recent studies have investigated how plausible this DNA preservation
and extraction could be. An Australian research team used buried Moa bones to
conclude that DNA would not survive longer than 6.8 million years. A pretty
impressive time span, however dinosaurs first appeared around 230 millions of
years ago, and died out almost 70 million years ago.
The international research group examined 150 leg bones of the Moa, a
giant extinct bird. The bones ranged between about 600 and 8,000 years old and
were collected from three different sites. Palaeo-geneticists led by Morten
Allentoft at the University of Copenhagen and Michael Bunce at Murdoch
University in Perth, Australia found the half-life of DNA to be 521 years. This
meant that after 521 years, half of the bonds in DNA had degraded, leaving half
of the genetic information unreadable.
DNA has a limited ‘life span’ or, more accurately, chemical stability.
Without the repair mechanisms present in a living cell, DNA decays and is eaten
by micro-organisms. After 6.8 million years, the DNA would be completely
destroyed. This makes finding intact DNA from more than 100 million years ago,
the ‘prime time’ of dinosaurs, very unlikely. As for DNA long enough to be
sequenced in a lab and studied, Dr Allenthoft says “such fragments will be gone
long before the 6.8 million year mark”. Such a result would shatter hopes that
we will be buying our tickets to a real Jurassic Park in the near future.
However, another recent study of ancient bones suggests there could be
a twist in the story. The team analysed bones cells (osteocytes) of two
dinosaurs, Tyrannosaurus
rex and Brachylophosaurus
canadensis. They claim to have
found remnants of osteocytes, which could contain DNA. These remains are yet to
be verified; and even if the cells contained DNA there may not be enough left
to confirm its origin. Osteocytes are comparatively ‘invincible’ and cannot be
destroyed and could be preserved in ancient tissue.
Dr Mary H Schweitzer, lead author of the study criticised the previous
study, stating that “These authors did not test fossils dating back older,
rather predicted that DNA would be gone by a certain time point”. She adds that
her bone samples do not agree with this hypothesis; “We have 4 independent
lines of evidence that there is material chemically consistent with DNA”
Even if DNA remains in these dinosaur bones, the slow degradation over
time may mean not enough remains to study the genetic information of the
animals through genetic sequencing. “We can’t demonstrate that the reactive
material inside these dinosaur ‘cells’ is dinosaur DNA without sequence.”
So where does that leave Jurassic Park? For long strands of DNA to have
any chance of surviving a 65 million year wait to the modern day, they would
require perfect conditions. So could there be an untouched, perfectly preserved
dinosaur genome under the Earth waiting to be discovered? “I would not
completely dismiss the idea that that DNA can survive longer than we think
under some extreme and rare conditions” explains Dr. Allenthoft, “but at the
moment there is nothing suggesting that we will ever get authentic DNA from
dinosaur bones”.
