Scientists tease DNA from eggshell of extinct birds
* By Richard Ingham in Paris
* From: AFP
* March 10, 2010 1:22PM
IN a world first, scientists in Australia announced today they had extracted
DNA from the fossilised eggshells of extinct birds, including iconic giants
such as the moa and elephant bird.
The achievement marks a major step towards drafting the genome of birds wiped
out by human greed, although the scientists warn this does not mean an extinct
species should -- or even can -- be resurrected in the style of Hollywood movie
hit Jurassic Park.
The team, led by Michael Bunce of Murdoch University in Perth, Western
Australia, say they isolated DNA from desiccated inner membranes in fossil
eggshells, found in 13 locations in Australia, Madagascar and New Zealand.
Ancient genetic material was coaxed from the eggshell of the moa (Dinornis), a
flightless cousin to the ostrich that reached up to four metres (13 feet) in
height and was hunted to extinction by New Zealand's Maori by the late 18th
century.
DNA was also extracted from the elephant bird (Aepyornis), like the moa and
ostrich a species of ratite, said the study, published in the Proceedings of
the Royal Society B.
Growing up to three metres (10 feet) high, the bird was wiped out by European
colonisation of Madagascar by 1700.
Other successes were reported using eggshells from an Australian owl and a New
Zealand duck of unknown date. The oldest egg sample was from an emu (Dromaius
novaehollandiae), some 19,000 years old.
But the team were unable to get DNA from far older samples in Australia,
estimated at 50,000 years old, from an extinct megafaunal bird called Genyornis.
The technique entails reducing the shell to powder, extracting the DNA with lab
chemicals and then amplifying it using polymerase chain reaction, or PCR -- a
standard tool used by forensic scientists, for instance, in getting the famous
"genetic fingerprint.''
Mr Bunce said the team extracted in each case only a tiny amount of DNA -- just
250 base pairs, the "rungs'' on the ladder-like genetic code, and this is less
than a fraction of one percent of the bird's genome.
"The point was proof of principle, to show that it can be done,'' he said in a
phone interview with AFP.
"We didn't go out to get very long pieces of DNA. That's obviously the next
step.''
Mr Bunce said the exploit would give palaeontologists a new window into
creatures of the past.
Until now, DNA has been teased from bones -- for instance, providing most of
the genome of the Neanderthal, our enigmatic extinct cousins -- and also from
preserved hair.
Eggshells, overlooked as potential source material, turn out to be
astonishingly robust at protecting DNA.
They are a tough biomineral matrix of calcium carbonate and are less prone than
bones to infiltration by bacteria, which contaminates samples.
And they are also plentiful. Archaeological sites have yielded harvests of eggs
plundered from nests by early humans, eager to keep a store of protein at hand.
It could be possible to go back further than fossilised eggs that are older
than 19,000 years, if the shells come from a permanently cold environment, the
scientists hope. But eggs that are completely "mineralised'' -- in other words,
like rock -- over hundreds of thousands of years are not a likely option.
Could the moa, the elephant bird or the dodo, which was hunted to oblivion for
food and hat feathers, ever walk again?
"We can reassemble the genome to get an idea of what an extinct species looked
like. But (resurrecting it) is still in the realm of science fiction. It's
completely hypothetical, and frankly not a debate I really want to have,'' said
Mr Bunce.
So far, scientists have only been able to synthesise a tiny strand of DNA,
creating around 200 artificial base pairs, he said. The human genome, by
comparison, amounts to around three billion base pairs.
"Some researchers have inserted certain genes into living species... (but) this
does not bring an extinct species to life,'' co-researcher Charlotte Oskam
pointed out.
"We think, like the mammoth, that it will be possible to do extinct genomes
using fossil eggshell but it is a huge leap to imagining we can clone an
extinct species. Personally I think it is unethical to recreate a species that
is extinct.''
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