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We may weep for the dodo, but could and should we bring this lovely bird back from the dead? De-extinction is the science of restoring lost species and it has been in the news for decades.
The story in modern times began in 1990 when Michael Crichton published his science fiction novel Jurassic Park, in which he imagined a world where scientists were able to bring dinosaurs back to life. Crichton imagined that polymerase chain reaction (PCR) technology could be a way to amplify (放大) tiny quantities of dinosaur DNA and thus build a living embryo.
Sadly, biologists soon realized that DNA in fact breaks down super-fast; even after 100 years, DNA from museum skins of dodos was decayed (腐烂) beyond repair. They could be sequenced (测定序列) using massive computational power, but then only with considerable uncertainty. And even if you capture a DNA sequence, there's still the problem of how you get living cells to read that sequence and express proteins that make the dinosaur or the dodo.
But why would anyone want to see mammoths, or something like them, roaming (漫游) present-day Siberia? Well, they were undoubtedly amazing beasts. As well as hunting them, our distant ancestors painted their likenesses in caves across Europe. Fascinating as they may be, there's some ecological justification for the project too.
It was this diversity of land surface, broken up by heavy limbs and randomly fertilised by faeces (排泄物), that supported so much flora (植物群). Without the mammoths, that diversity disappeared. Return them and landscapes would once again be with a variety of species, including flowers and bushes.
True, it's not de-extinction in the sense of bringing a long-dead species back to life. Instead it's more like making a "dodo" by engineering a modern pigeon, its closest relative, to become huge and flightless. The result would be a big, fatty pigeon that, whether it looked like a dodo or not, would probably fulfil some of its ecological roles.
As a palaeontologist, I would of course love to see living dinosaurs, mammoths and dodos. In some ways, though, I am relieved that the optimistic claims for cloning and genetic technologies have not been borne out. The slowdown gives us time to consider the outcomes—and hopefully avoid some of Michael Crichton's more fevered imaginings.
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