Can Genomics Really Cure Extinction?
What do Pongo pygmaeus, Dicerorhinus sumatrensis, and Panthera pardus orientalis all have in common?
Well, for one, they’re all currently doing slightly better on the evolutionary scale than Neovison macrodon (sea minks) or Thylacinus cynocephalus (Tasmanian tigers or Thylacine). While the first three organisms on this list (the Bornean orang-utan, the Sumatran rhinoceros, and the Amur leopard respectively) are all gravely endangered, both sea minks and thylacine have already become extinct. While not insignificant, they are only two creatures of many that have died out over the course of the Earth’s history, whether it be as a result of ecological changes, competition, overhunting, or geographical isolation resulting in a critically reduced gene pool.
This continual changing of the biodiversity of the planet has played a big part in creating the environment we currently live in, but it isn’t always necessarily a ‘natural’ change. Arguably one of the biggest impacts to global biodiversity has been the proliferation of the human race. We famously brought about the extinction of the dodo (Raphus cucullatus) in the 17th century because of habitat destruction and the introduction of predators, and our continued poaching of endangered species, particularly large African mammals, has led a number of animals to the brink of extinction.
In response to this influence, there are now a great many people who have set up organisations to help species that are nearing extinction. However, conservation efforts are not always as simple as introducing breeding programmes or building nature reserves; in many cases, we’re finding ourselves unable to prevent the gradual decline of endangered species.
An alternative approach, which has long been considered a staple of science fiction, would be to use cutting edge techniques to clone critically endangered or even extinct animals to ‘unnaturally’ boost their numbers. While bringing animals back from extinction sounds like something that couldn’t exist outside of a story book, thanks to the advances in genomics we’ve seen over the last two decades, the idea is slowly becoming more and more feasible. It is so plausible these days, in fact, that genomics heavyweight George Church and his team at Harvard University are now applying the theory to the Mammuthus primigenius, more commonly known as the Woolly Mammoth.
Despite considerable study, it’s unclear as to whether changing global temperatures or overhunting by early humans was more responsible for the decline in mammoth numbers. What is known is that the last population of woolly mammoths, who were isolated on Wrangel Island in the Arctic Ocean while their mainland brethren declined, completely died out around four millennia ago. What makes the mammoth so interesting, however, is that unlike many other long-extinct species, we have access to a considerable amount of intact genetic material. This is primarily due to mammoth remains having been exceptionally well preserved in oil pits or frozen conditions, and it means that, at a very basic level, we have the necessary resources to restore the species.
Earlier this year, George Church stated that he believed we could have mammoth-elephant hybrids in as little as two years. Instead of trying to breed pure mammoths, the team have elected to start by adding ‘mammoth characteristics’ to the genome of Asian elephants (Elephas maximus), a distant relative of the woolly mammoth. These characteristics include genes for the thick fur that gave woolly mammoths their name and blood adapted to extremely cold weather, amongst others.
“We’re working on ways to evaluate the impact of all these edits,” Church told New Scientist in February. “The list of edits affects things that contribute to the success of elephants in cold environments. We already know about ones to do with small ears, subcutaneous fat, hair and blood.”
Church has admitted that pure mammoths, which would not have to rely on elephant DNA templates, are still a long way away from being obtainable. Nonetheless, the initial work in the field has been promising and it has drawn significant public attention over the last year. One of the most high-profile effects is the film adaptation of Ben Mezrich’s recent book Woolly, which discusses Church’s work and which is due in the near future. Despite the hype surrounding the project, however, there are a number of challenges and ethical concerns that the team face when taking their work forwards.
One of the largest concerns is that the Asian elephant is itself an endangered animal, with an estimated global population of 700,000 (according to a report from the World Wildlife Fund in 2014). Using live Asian elephants for breeding woolly mammoths could negatively impact conservation efforts, significantly harming the species. As a result, Church has said that he will not use Asian elephants as surrogates as part of the project and is instead hoping to be able to bring his hybrids to term in the lab. He has publically acknowledged that such an undertaking isn’t something that would be possible with existing technology and his approach may mean that they are never able to breed mammoths, but he maintains his position. (It might not actually be as hopeless as it first appears. Recent advances have brought us much closer to being able to sustain prenatal organisms without live mother hosts.)
A more technical consideration is that cloning an organism is tremendously difficult. Even with modern techniques and knowledge, cloning an animal and sustaining it over a significant period of time has proven a challenge. For example, the first mammalian clone, Dolly the sheep, was the only live birth from 277 attempts at bringing a clone to term and even once she was born, she lived half the lifespan of an average sheep (6 years instead of 10-12).
An even more direct comparison would be the case of the Pyrenean ibex, one of the two subspecies of Spanish ibex, both of which are now extinct. The last of the species was a wild female called Celia, who was found dead in early 2000 after being crushed by a fallen tree. The researchers who discovered her collected skin cells from her ear and froze them in liquid nitrogen, with the intention of later using them to resurrect the species. Those skin cells were then used in a ‘successful’ cloning attempt in 2009; as a result, the Pyrenean ibex became the first animal to ever be made un-extinct. However, 7 minutes after the clone was born, it died because of severe lung defects.
Our understanding of prenatal development in mammals has advanced over the last 8 years, but there is still a lot that we do not understand. Mammalian cloning in particular has been something that we’re still nowhere close to perfecting, and this has large implications for attempts at undoing extinction like Church’s. Even if we are able to genetically alter an embryo to carry the same genes as an endangered or extinct species, if we cannot rear them to adulthood (and thereby fertility), there isn’t a chance of re-establishing them.
Finally, we also need to consider genetic diversity. Rapidly shrinking gene pools have been the cause of some creatures’ extinction and being able to clone one or two mammoths, for example, will likely have the same result as those ultimately doomed organisms. In the case of Celia, had the clone lived then it would still have been the last of its species, without a male to breed with. Even if a male had also been successfully cloned and raised to maturity, any offspring from the pair would be direct siblings and future generations would suffer from a catastrophically low genetic diversity. Ultimately, the Pyrenean ibex would have become extinct again.
With regards to the work being done at Harvard, even if we become capable of raising these mammoths, we would need to clone as many different genomes from the species as we could to ensure that the genetic diversity of the species was high enough to secure their proliferation. This would mean trying to find enough samples for hundreds of organisms and nurturing them to term. The amount of work necessary for such a feat would be colossal, especially with the current success rate of cloning.
If it were possible to bring back these long-dead creatures, it would be a fantastic achievement. Moreover, it might even have a positive impact on our environment, particularly in the case of the woolly mammoth. For one, they might offer a new route for conservation of Asian elephants, but they also have the potential to help combat climate change and snowmelt.
“[Mammoths] keep the tundra from thawing by punching through snow and allowing cold air to come in,” Church told New Scientist.
Of course, the purpose of this work is not solely to re-establish populations of extinct creatures. The concept of bringing back extinct organisms relies on a number of different biological fields, from genomics and cloning, all the way to habitat conservation and animal behaviour. Raising even a single mammoth to maturity would be a tremendous achievement for scientific endeavour and could help to teach us a lot about nature as a whole.
The advances in genomics since the completion of the Human Genome Project have opened up a number of novel pathways for the science to progress. Extinction studies are just one of many, but they might hold significant implications in the future of the planet as a whole and they provide an intriguing look at what possibilities genomics can offer us. Bringing back woolly mammoths might be a long way off, or even impossible, but if George Church’s team (and the others like them) are successful, our global biological diversity could look very different in 100 years.
What do you think about our chances of reviving extinct animals? Even if we could do it, should we? Do you appreciate my ability to not reference Jurassic Park at all in this article? Let me know in the comments!