An American-Russian collaboration to repopulate Siberia with woolly mammoths … or something similar

Jan 1 · 14 min read

Members of the Church lab visited the Siberian taiga, the past (and future) home of the woolly mammoths, and are more determined than ever to bring them back. Hear us out.

Back in 2009–2010 when the field of ancient DNA was gaining speed with whole genome sequences of many mammalian species becoming available, George Church, professor at Harvard and MIT and core faculty at the Wyss Institute at Harvard, had a brilliant idea. One among a bunch, anyways. He had after all predicted in the early 1980s that sequencing whole genomes would one day become cheap and mainstream. Now it is and did not only extend to extant species, but to the cave bear, woolly mammoth and ancient homo species. So why not use these sequences to really probe into the evolution of a species? Why not bring these extinct species back from the dead, Church wondered? It has always been his opinion that with the right tools and a few postdoctoral/graduate student years anything is possible. His laboratory specializes in synthetic biology and genome editing and resurrecting an ancient genome fits perfectly with this new frontier of biology. While no tools are currently fully adequate to complete such projects routinely, George Church wants to blaze the trail for multiplexing synthetic mammalian genomes. The possibilities are endless. The opportunity for the mammoth revival: enticing. Why not have woolly mammoths roaming the Siberian steppe once again?

In 2015, Dr. Church and I, as a newly minted PhD graduate, also asked why not? We were not the only ones. Thousands of miles away a father-son Russian duo were already preparing for the woolly mammoth arrival. Not only were they preparing for it, they argue it is essential for fighting climate change and human survival. Surely, we reached a threshold of people to start a de-extinction revolution?

Finally, this past August, Dr. Church and I were fortunate to travel to Siberia and take a closer look at a large environmental experiment being carried out by Sergey and Nikita Zimov at their Pleistocene Park. They need our mammoths. We all need their ambitious idea to succeed.

Pleistocene Park with Yakutian Horses. Credit: Eriona Hysolli

Many times as a young scientist I was asked the same two questions — what is the point of bringing back failed species and where are we going to house these mammoths? No species has ever been brought back from extinction before. Certainly none with the power of genome engineering.

I previously thought of this quest as an experiment to see how the extant elephant population is different from a closely related extinct species, and to probe it scientifically rather than speculate, albeit rationally, from their DNA sequences and available ancient remains. We know some jellyfish glow, and probing their sequence and bringing it to life in a culture dish gave us one of the greatest tools to visualize biological material. Now we have glowing cells and can essentially make any living thing glow. It is useful (and fun). When our revival efforts succeed, we could usher in a new era of preserving biological diversity of endangered species that are at risk of being lost forever, as well as reviving species that we have lost already. Collectively, we could invest more resources into protecting endangered species in the first place, however, humanity has a sad track-record of this, so perhaps preparing for the worst case scenario is not unreasonable. I carried these arguments with me at hand, until I met the Zimovs. Let’s begin a journey to bringing a lab idea, and a mammoth, into the real world.

The Journey Begins

Siberia is roughly 5 million square miles and consists of continuous permafrost. The permafrost is a deep soil level permanently under 0 degree C for two years or more, just beneath a few feet of the active level supporting the biomass of tundra and taiga. With the oscillations in global temperatures, the arctic zone has become warmer. Ice-rich permafrost thaws and generates depressions accumulating water, with a lake bed composed of peat and the thawed deeper permafrost layer. This carbon-rich ecosystem, particularly in regions where a lot of animals and plants were trapped in permafrost (yedoma), is ideal for anaerobic conversion of organic matter to methane gas. It is estimated that there are 1,400 billion tons of carbon frozen in the permafrost, the equivalent to the carbon estimated to have been released by humans by burning fossil fuels between the 1751 and 2014!

Even if a smaller portion of the carbon trapped in the permafrost is released in the atmosphere, the greenhouse gas methane traps more heat than carbon dioxide, and therefore, can potentially escalate the warming phenomenon. The Zimovs have a solution: Return the Siberian taiga into grasslands found in the mammoth steppe ecosystem that supported an estimated 10 tons of animal mass per square kilometer, among them one woolly mammoth. More on this later.

So we began our (very long) journey into Siberia with a stop in Yakutsk, the largest city of Yakutia. It is also known as the Sakha republic. Yakutia is roughly one million square miles with around one million inhabitants, the heavy majority of which are found in Yakutsk city. We were pleasantly surprised to find a replica of a woolly mammoth mother with her baby in the lobby of our hotel, which spurred many photo moments that will forever circulate among our research team. We have to make do with these until the real ones come along.

George Church and the resident woolly mammoth at the Polar Star Hotel in Yakutsk city, Russia. Credit: Eriona Hysolli

Due to their abundance, (dead) woolly mammoths are an important attraction and economic driver of the region. Stop by at any souvenir shop and mammoth ivory trinkets are ubiquitous and appealing. Yes, we bought a few. And yes, they are certified legal. (And if you happen to be around this part of the world, we strongly recommend Khachapuri restaurant…terrific Georgian food.)

We set off for Chersky (68° 44'N, 161° 23'E), a once booming north-eastern Siberia research town that has since devolved into abandoned apartments and rust. Upon arrival, our gracious hosts Nastia and Nikita Zimov enthusiastically greeted us then confiscated our passports. We headed towards a barge built by the Zimovs, which is impressively functional and warm, and a great place for getting to know our group more closely during our three-day stay there. As a side note, watch out for Katerina Zimov, Nikita’s eldest daughter and future chess grandmaster.

Aerial shot of Chersky flood lakes. Credit: Eriona Hysolli

We slowly made our way upstream of the Kolyma River towards Duvannii Yar, an observation point for yedoma layers, which are composed of organic matter trapped in iced soil. When the frozen surface layer of the Kolyma River melts in the summer, the banks continuously erode, thereby exposing vertebrate bones trapped in permafrost. We were able to motorboat to land from the barge and experience this phenomenon up close and personal.

Duvannii Yar — along the banks of the Kolyma River. Credit: Eriona Hysolli

While on a half-mile walk, we were able to find on the surface, and without much effort, around 20 bone fragments of various animals, among them a hip bone of a female mammoth and an equine upper jaw. It is quite remarkable for me to be involved in this kind of fieldwork, personally collecting specimen. A typical wet bench scientist’s workday comprises mostly of intense exploration of the indoor space of the laboratory with highlight trips to a seminar or the cafeteria just before closing time. What was fantastic to witness was how enthusiastic and inquisitive George Church was (to the surprise of no one who knows him) to find ancient bone remains. He trekked the river bank (with some tripping and falling here and there — he is very tall everyone) and dug through mud and soil to uncover several fragments we later examined. He also casually took a ride back to the barge sitting on top of the bow of the motorboat, as we later gathered to marvel at our bounty.

George Church unearthing woolly mammoth remains along at Duvannii Yar. Credit: Eriona Hysolli

According to the Zimov bone counting technology (more info in the book Paleontology in Ecology and Conservation pages 209–213), there were one mammoth, five bison, eight horses and 15 reindeer per square kilometer during the ice age. This does not take into account more animals like moose, musk ox, elks, saiga, sheep, woolly rhinos, cave lions, wolverines and wolves which roamed northern Siberia. We did not ourselves conduct quantitative measurements, but by judging the bones we did observe during our stroll along the Kolyma in Duvannii Yar, it is evident the soils are rich with prehistoric life remnants.

Why the woolly mammoth?

So why bring back an ecosystem like the mammoth steppe? Why are mammoths essential for the Pleistocene Park? Fundamentally, it entails combating the effects of global warming on permafrost melting by bringing in cold-adapted animals that will change the ecosystem to counteract , or at the very least slow down, the massive carbon release expected from the Siberian soil. The Pleistocene park is a 16 square kilometer nature reserve for rewilding the arctic. It is experimental as the area needed to be repopulated with large animals is 10 million square kilometers. The animals will trample the snow and therefore allow the cold arctic temperatures to penetrate deeper into the soil. Thus, the organic matter buried inside does not convert to CO2 and methane upon decomposition. Furthermore, the fertilization of the soil by animal excrement, allows for more nitrogen circulation in an otherwise closed nitrogen circle in the arctic. A slow nitrogen cycle means it takes a longer time for dead organic matter to decompose and restore the nutrients to its surroundings. A faster one supports a lusher grassland ecosystem, which in turn will support more wildlife.

George Church and Nikita Zimov on a motorboat at Pleistocene Park. Credit: Eriona Hysolli

But why the woolly mammoth? Why won’t a large animal like a bison or a moose suffice? Technically it doesn’t have to be a mammoth — an elephant will do. But it must be an elephant adapted, or engineered, for the arctic climate. An elephant or mammoth is needed for enabling a grassland ecosystem because of the presence of coniferous trees that make up the taiga, or boreal forest. This ecosystem is inactive as it is not a significant food source for any animals. It stops sunlight from reaching the soil for grasses to grow, nitrogen cycles slowly, and the dark green colors of the needle-like leaves absorb and trap heat that further warms the arctic climate. These trees need to go. That is correct. We need to kill trees to save the planet! Or so the Zimovs say. Cutting down the trees allows for grasses, bushes and smaller trees to grow that enable a richer ecosystem. A bulldozer can do this job, but a creature that creates a sustainable ecosystem is preferable to a machine that burns fossil fuels and releases greenhouse gases. A mammoth. Or an elephant. Or a hybrid. They like to kill trees, it’s what they do. We may need them in order to save us or buy us time.


One of the challenges with this idea, aside from actually editing the elephant genome to make it more similar to that of the woolly mammoth, and then breeding a few million of them, is the carbon footprint of the animals that will populate Siberia. The carbon footprint of an elephant, and we will make the safe assumption that a mammoth will have a similar figure, is estimated to be 26kg of methane per year. For all the gassy mammoths needed in Siberia (1/km sq), a simple calculation brings it to 0.00026 gigaton of methane released collectively each year. Even if we consider the 120kg methane/year a cow produces as a higher upper estimate, methane release in the atmosphere would be 0.0012 gigaton, but still much lower than the 1400 or so gigatons of carbon stored in the permafrost.

Permafrost layers at Duvannii Yar. Credit: Eriona Hysolli

Has the idea that animals foster grassland ecosystems been tested? Yes. This has been an experiment 20+ years in the making at Pleistocene Park, a largely self- and Kickstarter funded effort by the Zimov duo. After our river cruise, we headed towards the Northeast Science Station. It is a round building with a massive radio telescope at the top to ensure personal communication between God and Sergey Zimov. It also serves as a stop for any domestic and foreign scientists interested in arctic climate and geology. The park is one hour away from the station by motorboat along the Kolyma River, and we clearly see the difference in vegetation compared to the taiga ecosystem we observe on our drive there. There is a large area of open space with grown grasses, and further away a test are with different grass seeds currently tended by Nikita and his two park employees who will determine which is the best grass option for the park.

There is a decommissioned tank that the Zimovs used to topple trees. Nikita is also keen to share how he sawed 1000+ trees up until one day before his wedding day. It is the Russian way after all. There is a fence that has been erected to keep animals within the park, which are used to test how the animals maintain the grassland ecosystem. As for the animals, there are a lot of reindeer, yaks and sheep; a frustrated, but talented, javelin-throwing bison much too frustrated with the camera crew and the park dogs; a baby moose being fostered; dogs; and white Yakutian horses galloping freely at the river banks. And mosquitos. Lots of mosquitos. Even the calm George Church was evidently unsettled and happily and purposefully swung the electric bug zappers towards them, originally brought as a gift to the Zimovs. We also got a chance to approach one herd of wild horses slowly to get a better glimpse before the stallion set everyone in motion away from the excited onlookers. It’s an idyllic setting that points towards an idea that is not completely … well … out there.

The Zimovs have published most findings in well-established, and even elite peer-reviewed journals, albeit there is criticism surrounding some of their experimental designs. However, for the experiment to be tested even more successfully, the park needs more big animals — 13 bison are ready to be shipped to the park when there is adequate aerial transportation available. This is a serious challenge for populating a remote area of the world. The experiment is still ongoing, yet the early findings are promising, and Dr. Church and I are fortunate to see it in person.

The environmental impact is a compelling reason for us to de-extinct the woolly mammoth. They won’t be on display in a zoo, but rather let roam in in a protected zone within their natural habitat.

But, how we will deliver 10 million mammoths? We won’t.

So, what are we really talking about?

Our laboratory is working on an elephant-mammoth hybrid–dubbed “elemoth”. We have done extensive computational work to find all the differences between available African and Asian elephant genomes, and ancient genomes of several Mammuthus primigenius (woolly mammoth) individuals. This was done in collaboration with other Harvard University faculty and scientists worldwide.

We are also extremely appreciative of our collaborations with Russian scientists at the Academy of Sciences of Yakutia, the Yakutsk Mammoth Museum and the North-Eastern Federal University. One of the many pleasant surprises during our trip to Siberia was the generosity of these individuals to share their samples collected over various expeditions, many of them of newsworthy fame (Yuka and Buttercup mammoths). We would like to particularly highlight the collaboration with Dr. Albert Protopopov and Dr. Valery Plotnikov who made large mammoth remains available for us to sample.

From left to right: Eriona Hysolli, Dr. George Church, Dr. Albert Protopopov, Dr. Valery Plotnikov, Dr. Evgeniy Maschenko Credit: Eriona Hysolli

George is a very skilled drill operator and excitingly made quick work of handling large specimen of mammoth proportions. We drilled in half-sawed legs, whole legs and whole mammoth bodies. We samples fat pads, bone, muscle and tusks. I also found out that I (not George) could probably just about fully make it inside the skull of a woolly mammoth. Yes they are pretty big up close.

George Church and Eriona Hysolli setting up for frozen woolly mammoth sampling at the Yakutian Academy of Sciences storage unit. Credit: Eriona Hysolli

Our lab currently focuses on implementing genetic changes found in mammoths to an elephant cell. We concentrate mostly on genes that make the woolly mammoth adaptable to a cold climate and hope to generate an Elemoth that can comfortably populate Siberia. According to the latest elephant census, even accounting for all extant elephants, the number does not exceed one million. It is highly unlikely we will breed 10 million Elemoths. Not only are elephants endangered, cloning techniques are not particularly straightforward, even with domesticated species. Now, throw into the mix the long elephant gestation times (~22 months) and the few-year gap between delivering calves, and using elephants as surrogate for our cells appears slow and ineffective. However, these types of challenges do not deter George Church.

Eriona Hysolli sampling a woolly mammoth leg. Credit: George Church

Our strategy to begin addressing the development of baby Elemoths or mammoths is through in vitro development, a new area of developmental biology orthogonal to cloning. Scientists in our lab (Jeremy Huang) and the UK (Magdalena Zernicka-Goetz) have been able to grow artificial embryos in a dish that recapitulate early embryogenesis. This process starts with embryonic stem cells that undergo gastrulation in the presence of developmental factors found in the media used to culture the cells. As we grow more sophisticated with these approaches, we envision incubators with growing baby mammoths to scale up a generation of individuals that would otherwise be challenging and slow by traditional breeding techniques. Furthermore, we can engineer or replicate many known mammoth genetic backgrounds to eliminate in-breeding challenges, and also build in resistance to Elephant Endotheliotropic Herpes Virus (EEHV) that is otherwise fatal in Asian elephant populations. We believe we can subsequently deliver a population that can then sustain its own growth.

I hope it is evident that genome engineering is a reality that is here to stay and that that will improve our lives in more ways than one (ok yes, our assumption is if done responsibly). It is incredible to witness, even from the perspective of a boundary-pushing laboratory like ours, that such a large scale environmental idea has been pursued for decades by two individuals with strong beliefs and hope for the future of the Earth’s climate. An idea that is now more and more a newsworthy event, but that lingered for long periods of time in obscurity and dismissal. The latter is still somewhat the case given the funding dearth to achieve it, but it is a geoengineering idea that may fail, yet has precedent and merit. Is it the only idea that must be pursued to save us from global warming threats? It is very safe to assume that the answer is a resounding no. But for a complex challenge like climate change, betting on only one approach we all agree may not be the best strategy.

Eriona Hysolli is a postdoctoral fellow in the laboratory of Dr. George Church at Harvard Medical School, and a contributing writer for the Wyss Institute at Harvard University.

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