woolly mammoth

What the woolly mammoth can teach us about conservation today

MARCH 3, 2017 The shaggy megafauna that roamed Siberia and North America together with our ancestors captivate the imagination, but now it looks like they’re giving us a practical lesson in genetics that could help inform conservation efforts.

Scientists compared the DNA of two mammoths: a member of a dwindling island population with an individual from the booming herds of the more distant past. Their findings, published Thursday in the journal PLOS Genetics, provided some of the first concrete proof of the genetic theories describing how population size affects genetic fitness. Genomic meltdown” may have doomed the last herd of mammoths, a conclusion that on its face suggests dire consequences for modern endangered species, but that could also offer valuable insight into how to best keep today’s rarest creatures from crossing the threshold into extinction.

The furry beasts ruled the tundra for over a million years until climate change turned grasslands into forests and hungry humans arrived on the scene. These pressures caused the mainland population to go extinct about 10,000 years ago, but two pockets managed to survive millenniums longer.

Two arctic islands became their last refuge, with populations surviving on St. Paul island until a lack of fresh water did them in 5,600 years ago, leaving the species to make their final stand on the remote Wrangel Island, where they stuck it out for another 1,600 years.

Researchers compared the DNA of a 4,300-year-old Wrangel Island specimen with that of a 45,000-year-old mainland mammoth. Genomic diversity measures suggest that the mainland individual was part of a breeding population 43 times larger than the 300 remaining island mammoths.

They found that the island genome was damaged compared to that of the mainland mammoth, suggesting that the lack of diversity in the breeding pool may have led to a breakdown in the integrity of the gene pool. As a result, many island mammoths may have had poor senses of smell, and a new coat as the stiff hairs that protected individuals from the cold became soft and shiny. The mighty woolly mammoth became a “satin” mammoth.

Experts can’t be sure that these genetic changes caused the Wrangel population to die out, but Dr. Rogers finds the timing highly suspicious. “We found these bad mutations were accumulating in the mammoth genome right before they went extinct,” she told the BBC.

This result contradicts a 2012 paper, which found that while the genetic diversity did indeed drop after the shrinking population became isolated, it continued at a reduced but stable level for thousands of years, until some other cause drove the final nail into the coffin. “I’m personally leaning towards environmental change,” co-author Love Dalen, of the Swedish Museum of Natural History, told the BBC at the time.

Regardless of what ended the Wrangel Island mammoths, the study has great significance in the field of genetics, where genome evolution theory has long predicted that damaging mutations should pile up in small populations of organisms.

“The mathematical theories that have been developed said that [individuals in small populations] should accumulate bad mutations because natural selection should become very inefficient,” Rogers explained to the BBC.

The problem was that this accumulation takes a long time, making it difficult to confirm the theory by observing the change as it happens within a single species.

But the mammoth made just such an empirical observation possible.

“This is probably the best evidence I can think of for the rapid genomic decay of island populations,” Hendrik Poinar, an evolutionary geneticist at McMaster University who was not involved in the study, told The New York Times.

The confirmation may have serious consequences for efforts to prevent modern species from going the way of the mammoth.

“This is a very novel result,” Dr. Dalen, who published the DNA sequences this study was based on, told the BBC. “If this holds up when more mammoth genomes, as well as genomes from other species, are analysed, it will have very important implications for conservation biology.”

The paper identifies Asiatic cheetahs (fewer than 100 individuals), pandas (1600 individuals living in highly fragmented territories), and mountain gorillas (300 individuals) as examples of small populations in danger of suffering the same “genomic meltdown” as the mammoths.

Saving such species may be challenging, because once genes get deleted, it’s “difficult to see how genomes could recover quickly,” the authors write. “With small effective population sizes, adaptation through both new mutation and standing variation may be severely limited.”

Their work suggests the existence of a population point of no return, after which a species may never recover, no matter what careful protections are afforded to the endangered individuals.

But there’s a silver lining. A better understanding of the challenges facing small populations can help focus conservation efforts, and direct where limited funds should be best spent. Concentrating resources on preserving vulnerable species before their numbers dwindle could be a more cost-effective strategy than large expenditures on groups that have already suffered a great loss of genetic diversity.

“So if you can prevent these organisms ever being threatened or endangered then that will do a lot more to help prevent this type of genomic meltdown compared to if you have a small population and then bring it back up to larger numbers, because it will still bear those signatures of this genomic meltdown,” Rogers explained to the BBC.

Simply put, an ounce of prevention may be worth a pound of cure.


Scientists: We can clone a woolly mammoth. But should we?

FEBRUARY 16, 2017 This is not your parents’ “Jurassic Park.”

Harnessing the power of the CRISPR-Cas9 gene editing tool, a team of Harvard researchers is slowly coaxing woolly mammoth-like traits out of normal elephant cells. But recent claims that they’re close to creating a hybrid embryo have raised questions regarding the ethics of the procedure.

The issues range from questions of practicality – Should we risk impregnating an endangered elephant with an experimental embryo? – to an ethical Pandora’s box: Would the ability to bring species back from the dead derail conservation efforts?

But geneticist George Church says he believes letting the research continue would produce the benefits that go beyond the chance to see an extinct creature, suggesting the reintroduction of the woolly mammoth might mitigate climate change.

Except it wouldn’t be a mammoth, exactly.

“Our aim is to produce a hybrid elephant-mammoth embryo,” Dr. Church told the Guardian. “Actually, it would be more like an elephant with a number of mammoth traits. We’re not there yet, but it could happen in a couple of years.”

The phrase “mammoth cloning” may conjure up images of scientists extracting amber-bound DNA and incubating it in frogs as in the 1993 film “Jurassic Park,” but it means something quite different to Church.

Instead of re-creating an extinct organism, his team is trying to create a hybrid “mammophant.” Starting with the woolly mammoth’s closest living relative, the Asian elephant, Church uses the CRISPR precision gene editing tool to snip and splice in mammoth genes, granting mammoth-like characteristics such as a shaggy coat, extra fat, and cold-resistant blood.

“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 explained to New Scientist.

So far, with samples from a remarkably well-preserved 2013 find as a DNA guide, the team has accomplished 45 of these edits. If their goal were to perfectly re-create the mammoth genome, they’d still have thousands to go.

And they aren’t the only team taking this alternative cloning approach. Researchers in Chile are also trying to engineer a dinosaur out of a chicken by rolling back certain genes.

Church’s team says they’re only a couple years away from the next step, making the edits in an elephant embryo and studying its viability. The researchers believe they could turn skin cells of the highly endangered Asian elephant into embryos using cloning techniques.

And that’s the easy part.

Once they have a mammophant egg ready to go, they’d need a way to carry it to term. Ethics prevent using real Asian elephants as surrogate mothers because of their endangered status and high degree of intelligence, but Church has other plans.

“We hope to do the entire procedure ex-vivo,” or outside a living body, he told The Guardian. “It would be unreasonable to put female reproduction at risk in an endangered species.”

Some say the technology to grow a hybrid animal inside an artificial womb won’t be possible this decade, but The Guardian reports that Church’s lab is hard at work on the problem, already able to incubate a mouse embryo for ten days, about half of its gestation period.

Even if Church succeeds in overcoming all the technical hurdles, some wonder if the mammoth should be resurrected at all.

As Matthew Cobb, professor of zoology at the University of Manchester, told The Guardian: “The proposed ‘de-extinction’ of mammoths raises a massive ethical issue – the mammoth was not simply a set of genes, it was a social animal, as is the modern Asian elephant. What will happen when the elephant-mammoth hybrid is born? How will it be greeted by elephants?”

Church argues that the mammophant would join the fight against global warming, thus bringing concrete benefits to humans all over the planet.

“They keep the tundra from thawing by punching through snow and allowing cold air to come in,” said Church. “In the summer they knock down trees and help the grass grow.”

While such behavior could help keep greenhouses gasses locked in the permafrost, we’d need to get pretty good at mammophant cloning to bring back enough of the beasts to populate Canada and Siberia. Plus, as is often the case with geoengineering schemes, the effects would be uncertain. Scientists aren’t even sure whether the original loss of mammoths caused some climate change, or if the climate change killed the mammoths. In addition, there’s no guarantee that the helpful stomping behaviors are genetic, instead of taught by long-vanished mammoth parents.

And climate may not be the only unintended consequence. Other researchers worry developing such Lazarus-technology would endanger current conservation efforts. “De-extinction just provides the ultimate ‘out’,” said wildlife biologist Stanley Temple in a BBC interview. “If you can always bring the species back later, it undermines the urgency about preventing extinctions.”

Rather, we should focus on keeping the Asian elephant alive, paleobiologist and mammoth expert Tori Herridge wrote in a 2014 opinion piece for The Guardian.

“Sometimes the ice age world is so real to me that my throat aches and my eyes sting a little when I think about what we’ve lost, the animals we will never see,” she wrote. “But here’s the irony – if we feel like that about the mammoth, just think how our kids might feel about the elephant if we let it become extinct. We really ought to be focusing on that, and doing everything we can to stop it from happening.”