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Jurassic Park in real life

Sunday, 19. April 2015 - 16:17

Jurassic Park has a lot to answer for. It made the idea seem so simple. Take the DNA from a microscopic drop of dinosaur blood, preserved for 65 million years in the gut of a mosquito trapped in fossilised amber. Carry out a bit of jiggery-pokery involving chaos theory and Jeff Goldblum. Insert the dino DNA into the yolk of a crocodile’s egg and leave to incubate. Soon you’ll have a thriving menagerie of once-extinct beasts roaming the jungles of someone’s private theme park. The 1993 Hollywood blockbuster and Michael Crichton novel of the same name may not have invented the idea of “de-extinction” but they certainly put it out there as a concept. And like all good works of science fiction, it showed what goes wrong when scientists get above themselves. A rampant T-rex is, after all, the ultimate invasive species.

De-extinction, or the idea of bringing extinct species back from the dead, has come a long way over the quarter century since Jurassic Park was first published. It has now matured into a quasi-serious science and has even been the subject of its own TEDx conference. Of course, no-one is talking about bringing back dinosaurs – their DNA is lost for good – but some scientists are proposing to resurrect a range of other, more-recently extinct species such as the passenger pigeon and the gastric-brooding frog, both lost within living memory.

There are quite a few animals that have become extinct relatively recently that are potential candidates for de-extinction. They include the thylacine, or Tasmanian tiger, a large marsupial carnivore wiped out by sheep ranchers a century ago, the Pyrenean ibex which was hunted for sport until the last one fell dead in 2000, and the Steller’s sea cow, a gentle giant annihilated by hungry sailors in the 18th century.

Perhaps the most emblematic of them all is the woolly mammoth. There are few animals that better represent the lost world of the Pleistocene than these huge, shaggy relatives of the modern elephant. Woolly mammoths roamed the vast grassy steppe of Eurasia and North America for hundreds of millennia. The very last individuals were an isolated population of pygmy woolly mammoths that lived on Wrangel Island off northern Russia about 4,500 years ago.

There is no shortage of woolly mammoth tissue, some of it remarkably well preserved in the permafrost of Siberia and some scientists are confident that they can extract its DNA to bring the species back to life, either as clones or as a kind of mammoth-elephant hybrid.

Scientists in South Korea and Russia are collaborating on a project to clone a woolly mammoth by extracting a cell nucleus from frozen mammoth tissue and inserting its entire genetic material into the enucleated egg cell of an Asian elephant, which would also act as a surrogate mother. It’s the same basic cloning technique that led to the birth of Dolly the cloned sheep in 1996, except this time two species are involved rather than one – and one of them has been extinct for thousands of years.

The difficulties facing this particular de-extinction project are immense and few expect it to succeed. For a start, finding a good enough mammoth cell nucleus in preserved tissue is a tall order. Getting it to spark into life as a cloned embryo developing from the egg of another species is even more problematic – and that’s before the difficulties of pregnancy and birth.

At present, the oldest frozen material used to create a cloned mammal has been laboratory-stored cells of mice kept in a fridge for 16 years. Being able to clone a mammoth from tissue cells that have been frozen for thousands of years in less than ideal conditions presents a far more formidable set of obstacles.

Another de-extinction approach is to cut and paste large fragments of mammoth DNA into the chromosomes of an Asian elephant, thereby creating a genetically-engineered mammoth-elephant “hybrid”. Scientists involved in this project prefer to think about it as a way of making a cold-adapted Asian elephant with mammoth-like traits, such as hairy skin and layers of subcutaneous fat for good thermal insulation.

Scientists have already managed to sequence about half of the mammoth genome from the many small fragments of DNA isolated from frozen remnants of biological material, such as skin, hair, bone, teeth and even dung. They believe it is only a question of time before they achieve their ultimate de-extinction aim: a living hybrid. “We’re preparing to make a hybrid elephant that would have the best features of modern elephants and the best features of mammoths,” George Church, professor of genetics at Harvard Medical School, told the TEDx conference on de-extinction, held in Washington two years ago.

Since then, Professor Church has applied a sophisticated and revolutionary “gene editing” technique known as Crispr and has managed to get it working in elephant cells to carry out 14 precise changes to its genome. “We are now working on in vitro organogenesis [organ formation] and embryogenesis [embryo formation],” he told The Independent in an email.

Put to one side for the moment the question of “why would anyone want to do this?” and ask “can Professor Church and his colleagues be serious?” Would it really be possible to bring back mammoths, or at least a creatures resembling and behaving as them, using the synthetic life technology of molecular genetics and cloning?

Beth Shapiro, an evolutionary biologist at the University of California, Santa Cruz and expert on the ancient DNA of the Arctic, is something of a sceptic – despite writing a book called How to Clone a Mammoth: The Science of De-extinction. She points out the immense technical problems with this kind of work, mostly connected to the degradation of the DNA molecule after thousands of years. She says there are seven steps needed to clone a mammoth, starting with the DNA sequencing of the full mammoth genome, and ending with the birth and rearing of the mammoth hybrid or clone, and we haven’t yet cracked problem number one.

“It’s a hard problem and a problem that probably won’t be solved without new and different biotechnology to what’s available today. But if it’s what we want to do we will eventually learn how to sequence the complete genome of an extinct animal. And then we will have completed step one,” she says.

“While it’s not clear to me that there are compelling reasons to bring exact replicas of extinct species back to life, there may be compelling reasons to develop the technology to genetically manipulate living species. For example, this technology might be useful to provide a genetic “booster” shot for species that are critically endangered. So, instead of using this technology to bring extinct species back to life, we could use this technology to aid in the conservation of living and endangered species or ecosystems,” she says.

Hendrik Poinar, principal investigator at the ancient DNA centre at Canada’s McMaster University in Hamilton, Ontario, is more optimistic. Like Professor Church, he is excited by the idea of de-extinction. He believes the technical barriers are not necessarily insurmountable. “The revival of an extinct species is actually within reach,” he says. “I do believe it is. How you define ‘extinct’ may be at question. But I have no doubt that at some point we will be very close to having an organism that looks, feels and maybe even at some point behaves as its extinct ancestors did. ”

Which brings us back to the question: why? Even if it were possible to generate enough individuals to produce a viable, breeding population of mammoths or mammoth-elephant hybrids, what would be the point? Some conservationists believe that the entire enterprise is a potentially dangerous distraction from the main job of preserving the many thousands of threatened species we still have left in the world. For years they have argued that “extinction is forever” but if governments and corporations believe that it’s not, then this could fatally undermine efforts to preserve and protect what we have.

Stanley Temple, emeritus professor University of Wisconsin-Madison, believes that even if it works, the de-extinction approach could end up with a net loss of biodiversity, with less charismatic species in particular losing out. “Conservation biologists worry about de-extinction having a destabilising effect. If extinction is not forever, a lot changes... de-extinction might undermine conservation efforts. It could reduce concern over threats to biodiversity by giving us an unfortunate ‘out’,” he says.

Professor Church argues the opposite. He says that creating a cold-adapted Asian elephant would mean that the species could roam further north than its existing, threatened habitat. “Elephants are currently in danger as they overlap with human populations. If they could be readapted to places of minus 50C, where there is low human density, they would stand a higher chance of survival,” he says. Both have suggested that the present-day tundra landscape of Canada or Siberia could accommodate a latter-day population of mammoths. It would be an extreme version of the idea of re-introducing lost species into an ecosystem where they were once expelled, only this time set in the Pleistocene and not in the present.

Steve Connor

Source: 
www.independent.co.uk
Tags: 
animal world
De-extinction
DNA
extinct species
Jurassic Park