Dinosaur DNA may not exist, researchers say

[garrison@efn.org]

Seen in Nando Times on 7-june 1997

<b>Copyright  1997 Nando.net<br> Copyright  1997 Scripps Howard </b>
<p>

(June 7, 1997 00:31 a.m. EDT) -- When the original "Jurassic Park"
opened four years ago, the publicity hype was helped by a well-timed
scientific report that appeared to give some credence to its fantastic
story line: the resurrection of dinosaurs through fossilized genes.
<p>

The research journal Nature published evidence that DNA from the
dinosaur era -- though not from the giant reptiles themselves -- had
been recovered from 120-million-year-old insects preserved in amber.
<p>

The appearance of the sequel, "The Lost World," coincides with the
publication of another scientific paper on ancient DNA -- this time a
debunking one. After the most extensive series of studies ever carried
out on insects fossilized in amber, Jeremy Austin, Andrew Smith and
colleagues at the Natural History Museum in London found no trace of
genes millions of years old.   <p>

In the Proceedings of the Royal Society, they suggest that other
researchers who think they have extracted dinosaur-era DNA are
detecting modern DNA that has contaminated their samples.   <p>

In fact, many scientists have doubted all along that DNA molecules
were
durable enough to survive for millions of years. Extrapolations from
laboratory experiments suggest that, even in favorable conditions, the
chemical processes of oxidation and hydrolysis would destroy DNA
within
50,000 to 100,000 years.   <p>

The best preserving conditions for biological molecules such as DNA
are
found in amber -- fossilized tree resin. This honey-colored time
capsule makes insects trapped in the Jurassic age look as though they
had died yesterday.   <p>

Amber dehydrates insect tissues, protecting them from damp, and it
contains naturally antiseptic compounds called terpenoids that prevent
microbial decay. However, amber is not a perfect preservative, because
gases and some liquids can diffuse slowly through it.   <p>

Scientists who try to recover DNA from fossils use a technique known
as
Polymerase Chain Reaction. PCR is sensitive enough to detect and
amplify just a few molecules in a sample and this makes it extremely
vulnerable to contamination.   <p>

All researchers in the field are aware of the danger and they make
strenuous efforts to minimize the risks of contamination. However, it
is almost impossible to exclude all modern DNA, for example from
airborne fungal spores or shed human cells, which may be amplified by
PCR and mistaken for ancient genes.   <p>

Austin and Smith point out that several other laboratories have tried
and failed to find fossilized DNA, using different methods and sources
of amber. "This lack of replicability does not by itself disprove the
existence of ancient DNA in amber-entombed insects but does put a
giant
question mark over previous studies," they say.   <p>

Scientists who have reported finding ancient DNA in amber, such as
George Poinar at Oregon State University, Raul Cano at California
Polytechnic State University and Rob DeSalle at the American Museum of
Natural History, are not ready to retract their claims.   <p>

They are encouraged by recent studies of other biological that some
amino acids (the building blocks of proteins) remained intact after
millions of years and suggest, by correlation, that DNA might have
survived, too.   <p>

But Bryan Sykes, an independent specialist on ancient genetics at
Oxford University's Institute of Molecular Medicine, commented in
Nature: "Austin et al have effectively snuffed out this glimmer of
optimism."   <p>

Even if dinosaur-era DNA turns out to be a laboratory artifact,
experiments have confirmed the survival of much more recent genetic
material -- many thousands rather than millions of years old -- from
people, animals and plants. The oldest authenticated records are for
DNA fragments extracted from the corpses of woolly mammoths that have
lain frozen in the Siberian permafrost for 40,000 to 100,000 years.
<p>

Scientists have obtained ancient DNA from a wide range of
archaeological samples, including Egyptian mummies dating back to 500
B.C., the 5,000-year-old Tyrolean ice-man, several extinct species of
animals and birds and dried plant seeds. The genetic evidence being
assembled will be important for a wide range of academic disciplines.
<p>

For instance, the genetic study of wheat grains from archaeological
sites in the Middle East and Europe, dating back 10,000 years, is
beginning to give a wealth of information about the origins of
agriculture. The conventional theory is that wheat was domesticated
just once, by a single group of farmers, but the new evidence shows
two
distinct genetic populations of ancient cultivated wheats that are too
different to have evolved from a single parent in the time available.
<p>

The chemical remains of ancient DNA are just small fragments of the
original molecules. A complete set of genes would be needed to have a
hope of resurrecting extinct species, possibly by putting it into the
egg of a related animal. Even so, a film that brought our human
ancestors back to life and pitted them against saber-toothed tigers
would be more plausible than "The Lost World's" dinosaurs.   <p>

<b>By CLIVE COOKSON, The Financial Times</b><p>