Sixty-six million years after they disappeared from the face of the Earth, the dinosaurs have become animal celebrities; children everywhere are fascinated by them.
Tyranosaurus rex and diplodocus are as familiar to youngsters nowadays as lions and bears were to previous generations. Museums give the huge beasts prime exhibition space. Advertisers, toymakers, even Duffy’s Circus, are on the dinosaur band-wagon.
Credit for resurrecting the ‘terrible lizards’ must go to Hollywood. Blockbuster films feature scientists cloning dinosaurs on remote tropical islands, where the fearsome beasts inevitably run amuck. According to one story line, primordial biting midges, trapped in tree resin solidified into amber, have dinosaur blood in their stomachs from which DNA is extracted. Such insect specimens exist but is harvesting dinosaur DNA a real possibility?
Beth Shapiro, an expert on ancient DNA, examines the question in her new book How To Clone A Mammoth, The Science Of De-Extinction. Dinosaur enthusiasts, alas, will be disappointed. According to Shapiro, resurrecting even the passenger pigeon, which vanished just a few decades ago, would be very difficult. There is no prospect whatsoever that dinosaurs will be roaming a wildlife park any time soon.
The main focus of ‘de-extinction’ science is the mammoth. If any large extinct mammal can be brought back from the dead, this hairy elephant can. Shapiro, however, is sceptical that it can be done. The cold- resistant elephant began its decline around 20,000 years ago when climate change reduced its rich sub-Arctic grasslands.
It became extinct on the mainland 8,000 years ago but small populations survived on islands for a further 4,000 years.
As the permafrost thaws due to global warming, mammoth carcases are coming to light, spawning a bizarre smuggling industry. The mammoth can’t be listed under the Cites treaty, which prohibits trade in the body parts of endangered species; the creature is not ‘endangered’ but ‘extinct’. Elephant ivory is being ‘laundered’, passed off as mammoth sourced, aggravating the poaching crisis in Africa.
However, virtually complete specimens, coming to light before the criminals get to them, are benefiting de-extinction science. A Japanese team hopes to clone a mammoth in the next few years. Harvard researchers are trying to insert mammoth genes into elephant DNA, while Pleistocene Park in Siberia is recreating the Ice Age habitat needed to support any animals the scientists create.
Shapiro points out, however, that DNA begins to deteriorate on death and that only short sequences of mammoth DNA have been unearthed. Fragments tend to be 30 to 90 base-pairs long, and damaged.
Trying to link these together to recreate a four million-pair genome is the ultimate jigsaw puzzle. The mammoth’s closest living relative is the Asian elephant. Its genome could serve as a rough guide but it has yet to be sequenced.
Around 80% of the less-closely related African elephant genome is known. If a ‘best guess’ mammoth genome can be constructed using that, it will then be inserted, Dolly the Sheep-style, into a surrogate elephant, an exceedingly long shot.
In an alternative approach, we could ‘breed back’ the mammoth; selectively engineering Asian elephants for mammoth-like anatomical features and adaptations to cold conditions. However, their breeding rate is so slow that scientists engaged in the enterprise wouldn’t live long enough to see meaningful results.
Any creature produced might resemble a mammoth but, genetically, it would be a new species.
Inserting genes for salient mammoth characteristics into an elephant nucleus to produce a mammoth-resembling specimen might also be feasible. The resulting creature, however, would still be an elephant.
Even if we succeeded in recreating such a creature, formidable problems would then emerge; how do we support a species, about whose needs lifestyle and breeding biology we know very little? Should we try to de-extinct creatures at all? Is it ethical to do so?
Shapiros’ book is fascinating.
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