* Risa Aria Schnebly (she/they) is a PhD candidate at Arizona State University. They work at the intersection of environmental history, the social sciences, and the environmental humanities to study the history of (de-)extinction and to test whether the idea of “reversing” extinction affects people’s attitudes about conservation. They are also interested in what conservation narratives and strategies make young people feel hopeful about environmental futures— whether these are stories of conservationists working on the ground or scientists “resurrecting” woolly mammoths…
[This is Part 1 of a two-part essay. You can find Part 2 of this essay here.]
If there’s one thing most people know about extinction, it’s that “Extinction is Forever.” That catchphrase is ubiquitous, popping up everywhere from middle schoolers’ biology textbooks to guilt-inducing conservation advertisements. But over the last decade, reports of scientists attempting to accomplish “de-extinction” projects have begun to challenge that notion, with headlines like “What if Extinction is Not Forever?” or “Should We Bring Extinct Species Back from the Dead?” appearing time and time again in major mainstream news outlets and science journals (Sherkow, 2013; Schultz, 2016).
The idea of reversing extinction may seem novel, but the “de-extinction” projects making headlines today are only the latest iteration of a much longer history of scientists attempting to recreate lost species. The history of such projects, which fall under the broader label of “resurrection biology,” reveals how scientists have continually reconstructed their ideas of what a species is and why it is valuable, as well as how the idea of “bringing back the dead'' has continually been an object of scientific fascination and emotional longing. But before getting into that history, let’s lay some groundwork for how modern de-extinction projects work, why they’re happening, and the debates that have arisen in their wake.
Modern “de-extinction” projects use genetic engineering to recreate the genomes of lost species. First, de-extinction scientists sequence the genome of an extinct species, like the woolly mammoth, and compare it to the genome of a close living evolutionary relative, like the Asian elephant. This is to identify differences between the two. Then, they edit the genome of the Asian elephant to more closely resemble that of the woolly mammoth, using tools like CRISPR-Cas9 to rewrite stretches where the most important “mammoth-like” genes appear, like genes for thicker fur. If done correctly, the process should create a hybrid mammoth-elephant genome that can eventually be inserted into an enucleated elephant egg, implanted into a surrogate mother (or in the case of the mammoth, an artificial womb), and used to give rise to a creature that looks and acts like a woolly mammoth once did.
Three of the species that are the subject of some sort of de-extinction project, including the woolly mammoth (left), the thylacine (top right), and the passenger pigeon (bottom right). Source: https://www.thecollector.com/extinct-animals-scientists-trying-bring-back/
De-extinction projects such as this are underway for a number of famously extinct species, including passenger pigeons, thylacines (also called Tasmanian tigers), heath hens, and of course, dodos. The goal is not to create a singular organism of an extinct species to live out its life as a public spectacle in a zoo, but to create entire populations of the de-extinct organism to rewild the landscapes where the extinct species once roamed (Novak, 2018).
The scientists behind de-extinction argue that restoring the ecological role of extinct species to earth’s environments can have ecosystem benefits and help combat biodiversity loss. Re-introducing massive flocks of passenger pigeons, which once routinely brought healthy disturbance to eastern US forests, for example, could allow a wider diversity of species to thrive in the region (Revive & Restore). And putting woolly mammoth proxies in the Siberian tundra may help restore the steppe ecosystem that supported a wider diversity of species in the past, and may even fight climate change by keeping the permafrost from melting and releasing many metric tons of greenhouse gasses.*
[* Trampling mammoths once cleared the ground of snow, allowing the cold Arctic air to better penetrate the permafrost and keep it frozen for longer: an effect de-extinction scientists believe they can replicate with mammoth proxies (Reiderer, 2018).]
But, that’s all just in theory. There is no shortage of hurdles standing between de-extinction scientists and their goals. The amount of gene sequencing, editing, and testing that scientists have to do to create a hybrid proxy genome is time-consuming and extraordinarily expensive (though with over $225 million dollars in funding for Colossal Biosciences (Metinko, 2023), the latter might not be so much of an issue). But even once scientists have a suitable genome, an egg carrying that genome must still be implanted within an appropriate surrogate mother. Then, the offspring must somehow learn to behave like a member of an extinct species without any members of that species around to teach it. And if scientists manage to figure all that out and successfully create entire populations of these proxy organisms, there’s also the matter of where those de-extinct species are going to live, and whether local people will be happy about their presence.
Ben Lamm (left) and George Church (right), founders of Colossal Biosciences, which promises to have “resurrected” mammoths and thylacines within the next five years
Notwithstanding these difficulties, the organizations at the forefront of de-extinction efforts are promising success— and soon. Dallas-based biotechnology company Colossal Biosciences, which is financially backed by a number of celebrities and Silicon-Valley billionaires, promises to have the first “reborn” thylacine by 2028, and the first mammoth proxies by 2027 (Colossal).
Challenging the Nature of Extinction
The prospect of de-extinction scientists’ success has raised questions about how to define what species the de-extinct creatures belong to, and whether de-extinction counts as a legitimate reversal of extinction. Such a question is a philosophical one, having to do with the definition of extinction itself. But unlike the intimately related species concept, philosophers of science have paid little attention to how extinction should actually be defined. Since the concept was first established as a result of Georges Cuvier’s work with mammoth and mastodon fossils in the late 1700s, scientists have largely defined extinction as the end of a species, with little elaboration on what the “end” exactly means (Delord 2007). Most biologists accept the following basic definition: “[Extinction is the] end, the loss of existence, the disappearance of a species or the ending of a reproductive lineage.” In the last decade, though, and especially since the rise in popularity of the concept of de-extinction, more philosophers have begun attending to the ontological dimensions of this fundamental biological concept (Siipi and Finkelman, 2017; Finkelman, 2018).
Georges Cuvier’s drawings of mastodon versus Asian elephant teeth, which helped him establish the reality of extinction. Source: https://americanhistory.si.edu/elephants-and-us/elephants-and-idea-extinction-0
De-extinction scientists have rarely publicly engaged with questions of species authenticity, and have offered divergent takes on the issue when they have. Ben Novak, a geneticist who heads the passenger pigeon de-extinction project at the nonprofit Revive & Restore (which launched in 2012 and was largely responsible for popularizing the term “de-extinction”), concedes that de-extinct organisms should not be defined as members of the extinct species that scientists are aiming to replicate. Defining de-extinction as the replacement of an extinct organism by a purposefully adapted proxy, he argues that de-extinction projects are little more than an extension of restoration ecology, which has a long history of “restoring” ecosystems by replacing locally extinct populations with translocated populations of related subspecies (Novak, 2018). On the other hand, Andrew Pask, the head scientists at the TIGRR lab, which works with Colossal on thylacine de-extinction, said in an interview with ABC Australia that because the genomes of the de-extinct thylacine proxies will be over 99.9% similar to the extinct thylacine proxies, he feels “really comfortable saying that [the de-extinct creature] is a thylacine” (Pask, 2023).
Regardless of precise definitions, de-extinction scientists— and even more so, reporters who cover their work— often talk about de-extinct proxies as if they are equal to extinct species, using rhetoric about “resurrection” or “revival” rather than “recreation” or “replacement” to promote their projects. The idea of resurrection in particular has taken on moral overtones in de-extinction discourse, with some de-extinction proponents arguing that “resurrecting” extinct species is a path to human “redemption,” by allowing us to bring lost species back to “a world that misses them” (Brand, 2013a; Brand, 2013b ).
While modern de-extinction scientists may be using novel technology to accomplish their goal of “bringing back” the dead, the goal of reversing extinction has existed nearly as long as the concept of extinction itself, and with it, the idea that reversing extinction is a form of atonement. The historical projects to attempt reversing extinction, which all fall under the umbrella term “resurrection biology,” have occurred in different times, places, and with different technologies. Still, a scientist in nearly every resurrection biology project has expressed something akin to the idea that reversing extinction could be a way of making up for past wrongs.
Back to the Era of “Back-Breeding” Aurochs
The first scientist to imagine “reversing” extinction was Feliks Pawel Jarocki, a Polish zoologist and entomologist. In 1835, Jarocki proposed that selective breeding techniques could be used to “breed back” the extinct aurochs, a gigantic, aggressive species of cattle that is the ancestor of all modern cattle. The aurochs once ranged across Europe and down to northern Africa, but after being hunted for centuries, they were confined to the Jaktorów Forest in Poland, until the last living individual died in 1627 (Rokosz, 1995; van Vuure, 2005). Jarocki suggested that by mating different cattle with aurochs-like qualities, such as longer horns or a more aggressive temperament, one could get an animal that looked and acted like the aurochs once more.
An illustration of a man slaying an aurochs, from Conrad Gesner’s Historiae animalium (1551–1558). The above image is a reproduction printed in 156. Source: https://www.cabinetmagazine.org/issues/45/wang.php
Though Jarocki never attempted to carry out this plan, two German zoologist brothers carried out experiments similar to Jarocki’s proposal in the 1920s. Lutz and Heinz Heck, sons of Ludwig Heck, who directed the Berlin Zoo from the late 1800s through the 1930s, began experimenting with back-breeding aurochs in the 1920s, around the time each brother was finishing up his respective zoology degree. Each Heck brother ran their back-breeding program independently. Heinz started his breeding program at the Hellabrunn Zoo in Munich in 1921, aiming to create a new breed of cattle that resembled the aurochs (Allen, 2019). Dismayed at human-caused extinction, he hoped that his back-breeding project could lead to the reintroduction of a species that humans had once driven away. He bred Scottish highland cattle with long horns with Hungarian and Podolian cattle, as well as Alpine cattle with shorter grey or brown hair (Heck, 1951). In 1932, Heck declared that he had successfully bred those cattle together to recreate an aurochs. Modern genetic comparisons of Heinz’s breed of cattle to aurochs remains reveals notable differences between the two, suggesting that Heinz did not actually succeed at “reversing extinction” (van Vuure, 2005). Nonetheless, in a 1950 report on his experiments, Heinz called the creation of the Heck cattle “a miracle” and argued that “if man cannot be halted in his mad rage for destruction of himself and all other creatures, it is at least a consolation if some of those kinds of animals he has already exterminated can be brought to life again.”
Heck cattle in Unteres Odertal National Park, Brandenberg. Source: Wikipedia Commons
Lutz started his own back-breeding program a few years after his younger brother, but with a different priority: recreating the aurochs’ behavior, rather than their appearance. Lutz was less concerned with restoring the aurochs to benefit the environment, and more interested in recreating the conditions of a long-lost time: that of the Teutonic knights, whom Lutz revered as heroes from a more noble era. For his back-breeding project, Lutz also used Corsican cattle to replicate the hair length and color of primeval aurochs, but he bred them with French and Spanish fighting bulls, which he selected for their aggressiveness, agility, and “blood lust” (Heck, 1954). He declared a successful recreation of the aurochs in 1938.
Through the years when the two brothers were carrying out their back-breeding experiments, Germany was changing. The National Socialist German Workers Party was coming into power, with Hitler at the forefront. Each brother recognized that they needed the support of the Nazi party to be able to reintroduce their cattle into the landscape. Heinz Heck applied for a professorship with the Nazi party in the early 1930s in hopes of gaining their support. Instead, the Nazis questioned Heinz’s character because he had been married to a Jewish woman during World War One, which was enough justification to imprison Heinz in Dachau concentration camp for four whole years, beginning in 1933.
Lutz Heck (far left) and Hermann Göring (far right) looking over a map of the Białowieża Forest, containing figurines of game animals. The horn on the table may have belonged to a Heck aurochs. Source: https://www.cabinetmagazine.org/issues/45/wang.php
Lutz Heck had much better luck allying himself with the growing Nazi party. In 1933, he became a member of the National Socialist German Workers Party and a patron to the SS (Schutzstaffel, meaning “Protection Squadrons”), the Nazi’s main paramilitary force, which carried out most of the surveillance and mass violence that pervaded Nazi Germany. Lutz also became a close friend to Hermann Göring, who was one of the most powerful people in Germany during the Nazi regime, and who created the Gestapo, or secret police. Göring, who shared Lutz’s love of Teutonic myths and desire to restore the German landscape to what it was at a “nobler” time, especially helped advance Lutz’s career, and funded his back-breeding experiments (Driesen and Lorimer, 2016).
Göring and other Nazi political leaders were unsurprisingly interested in the Lutz’s back-breeding work; many Nazis were self-proclaimed conservationists, who argued for fostering the German people’s sense of connection to the land as a route for advancing a certain kind of nationalism. Modern scholars tend to agree that Nazi environmentalism was largely lip service (Driessen and Lorimer). Even so, many modern German conservation laws were originally written under the Nazi regime, including laws that protect specific species and natural land areas throughout the country (Uekötter, 2007). Perhaps most notably, in 1935, Göring helped spearhead the passage of the Reich Conservation Act, one of the first pieces of legislation in German history that prioritized nature conservation at a national level, making it the responsibility of the German government (though they made plenty of environmental exceptions for the “essential business” of war). Plus, many Nazis were animal lovers— Lutz Heck gifted Göring with a pair of lion cubs, which he turned back over to the Berlin Zoo once they grew too big to care for (Driessen and Lorimer, 2016). Heinrich Himmler, the German official who oversaw the Nazi regime’s horrific genocidal programs, tried to ban all hunting of animals. Even Hitler himself was purportedly a vegetarian (Tolschuss, 1937).
Göring and other Nazi’s love of nature was intertwined with their desire to foster a population of reproductively “fit” people, which naturally gave rise to efforts to “breed back” superior ancestral breeds of animals. Göring funded the continuation of Lutz’s aurochs back-breeding, and helped him start projects to captively breed the endangered European bison and the extinct tarpan, a species of horse. Lutz released his “aurochs” into the Rominten Heide hunting reserve in 1938 (Driessen and Lorimer, 2016). By the end of World War Two, though, most of Lutz’s cattle, which he kept in the Berlin Zoo, had been killed in Allied bombing raids. His brother Heinz, on the other hand, continued his back-breeding experiments after being released from Dachau, and eventually released forty cattle into Prussian forests (Allen, 2019). Heck cattle, as the breed is now known, persist in the European landscape to this day.
Hermann Göring on a hunting expedition. Source: Wikimedia Commons
Modern biologists tend to consider Heck cattle a new strain of cattle rather than a resurrected aurochs (van Vuure, 2005). Even so, the Heck brothers’ experiments inspired other back-breeding projects. As of 2023, one modern back-breeding project seeking to recreate the aurochs, called the Tauros Programme, is ongoing and seeking to repopulate European forests with de-extinct aurochs as part of the organization Rewilding Europe. However, one earlier back-breeding project started much earlier, seeking to recreate an entirely different mammal in South Africa. (This is discussed in Part 2.)
* * *
The Heck brothers did not have to deal with the public scrutiny that surrounds modern de-extinction projects. Nor did they have to deal with ethical and philosophical debates about whether de-extinction is a legitimate “reversal” of extinction or whether human intervention in nature has gone too far. The “recreation” of the aurochs was no more technologically advanced than everyday breeding. The organisms only had to look and act like the Heck brothers’ imagine of an aurochs for the projects to be considered a success.
Nonetheless, the back-breeding project inspired awe through the idea that its success signaled the return of a long-lost, romanticized time period, as well as (at least for Heinz) the idea that the creation of those back-bred creatures was a form of “consolation” for the destruction humans have caused in the natural world. While the technologies, locations, and species at the center of resurrection biology projects have shifted, such awe has remained. The emotionally-loaded discourse, full of awe and optimism, that surrounds de-extinction projects today is an echo of these earlier attempts to bring species back from the dead.
References
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Brand, S. 2013a. Opinion: the case for reviving extinct species. National Geographic News. March 12, 2013a. https://www.nationalgeographic.com/news/2013/3/130311- deextinction-reviving-extinct-species-opinion-animals-science/.
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