This article was originally published in Genetic Literacy Project and written by David Warmflash, MD.
Teasers are already running for what is expected to be the blockbuster movie of the summer, Jurassic World, the follow-up to Stephen Spielberg’s 1993 classic Jurassic Park, in which scientists used cloning to bring dinosaurs back to life. Twenty-two years later, Isla Nublar now features John Hammond’s fully functioning dinosaur theme park—and then all hell breaks loose.
It’s bound to be immensely entertaining, but as for plausibility? Reviving an animal from Earth’s Mesozoic era (~245-65 million years ago, when the dinosaurs lived), is theoretically possible, but highly improbable. First of all, cloning would depend on transfer of the dinosaur genetic material into the egg of an extant (currently living, not extinct), yet related, animal. The best available candidates are birds; if we want to revive a large dinosaur, we’d need a bird that lays large eggs, such as an ostrich. It’s not clear that this would be good enough, but to host the dinosaur genome through development, a large bird egg would be the best bet.
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As for the DNA, in certain environments, it can remain stable in bones for millions of years, and preserved genetic sequences can be analyzed for fascinating evolutionary studies. On the other hand, obtaining the entire genome of a dinosaur is unlikely, and filling in the missing sequences with modern genes would be useful, only if there are very few missing sequences.
Alongside the technical issues, some have raised possible ethical issues. For instance, the first generation would have no parents, they would have predators, and, as made clear in Jurassic Park, they could prey on other species. Getting them into balance with our current biosphere could be tricky.
On the other hand, consider an animal that has gone extinct much more recently than dinosaurs and the ethics and the science become easier. We enter more realistic territory from the perspective of technical feasibility. This is due both to the availability of extant egg donor closely related to the extinct animal and to an increased likelihood that all, or nearly all, of the extinct animal’s genes will be preserved in its fossilized remains.
For this reason, over the last two years, media have gone wild over the story of a woolly mammoth that died approximately 40,000 years ago and whose remains were discovered in Siberia. Woolly mammoths have been extinct only for 10,000 years (small groups of mammoths persisted several thousand years longer in a few locations), compared with the most recent dinosaurs that have been extinct for 65 million years.
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At the same time, because of the cold environment of Siberia, not only are the bones of the mammoth a good source of DNA, but even soft tissues are well preserved, including blood and bone marrow (good sources of DNA). Either the entire genome is available, or there are only small gaps that scientists can fill with synthesized sequences. The complete genome can be transferred into a host egg—in this case from an Asian elephant, which is much more closely related to a mammoth than an ostrich is to a dinosaur. Finally, the egg containing the mammoth genome can be implanted into an elephant to be a surrogate mother for a 22-month pregnancy, and throughout childhood.
As with dinosaurs, the idea of cloning mammoths has sparked an ethics debate. In the case of the mammoth, some argue that humans actually have a moral obligation to revive the species, based on the idea that humans hunted the giant animals to extinction. This rationale is contradicted by a recent study by British and Swedish scientists, pinning the extinction on climate change, namely the warming of Arctic regions as the most recent ice age came to an end. But nature’s possible role in mammoth extinction is not the reason why the mammoth cloning project has opponents.
“You’re dealing with highly intelligent, highly social animals,” says paleobiologist Tori Herridge of London’s Natural History Museum, whose concerns center on the fact that the elephant surrogates would not be an exact match of the mammoth’s natural parent.
Moving to more recent times since extinction, the ethical arguments against cloning get weaker, right up to the time since extinction being zero. In other words, we can extend the idea of species revival cloning to cloning for preservation of species not yet extinct, but endangered. On this issue, some say that cloning is so inefficient that efforts to preserve dying species with cloning techniques would be futile. But other experts believe it is only a matter of time before cloning becomes a viable option for species conservation. As with other applications of cloning, the rapid development of technology is sure to open up some fascinating possibilities, along with a host of debates.
Reprinted with permission from the author.
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