The Rise of Necrofauna and the Ethical Dilemma of De-Extinction

A Columbian Mammoth skeleton (Mammuthus columbi) with tusks, which was found in La Brea Tar Pits and is now in Page Museum, Los Angeles

In the not-too-distant future, at least four animal species and a tree now classified as being extinct are expected to be mostly biologically revived. The rise of the necrofauna, as biologist Britt Wray calls it, brings tremendous hope, but also concerns that humanity has never before faced.

Although the existence of necrofauna is still hypothetical, one animal has already undergone the de-extinction process: the Pyrenean ibex. It is hard to call that a success story just yet, however, as the cloned calf only lived for minutes in 2003 before it died due to a lung defect.

“It’s the only (de-extinction) case so far for an animal,” Wray, a researcher at the University of Copenhagen’s Center for Synthetic Biology and author of The Rise of the Necrofauna, told Seeker. “However, depending on how far you want to stretch the definition of ‘de-extinction,’ the genetic rescue of the American chestnut tree, which is currently underway, may count.”

According to the organization American Forests, the American chestnut was once the predominant tree species in eastern US forests. Billions of the trees used to tower over the landscape, before a blight began to kill them off beginning around the year 1904. The blight’s source — a pathogenic fungus called Cryphonectria parasitica — was introduced into the US from Japanese nursery stock that same year. In just 1-2 decades, all of the American chestnut trees had died.

In 1989, a breeding program created by the American Chestnut Foundation started to produce hybrid trees that are indistinguishable from the original American chestnut trees, but include a small amount of genetic material from the Chinese chestnut tree. The process involves “backcrossing,” whereby trees are crossed and then bred via successive generations as closely back to the original species as possible.

“It’s probably not the best tree we can achieve, but it’s good enough to start planting,” said Kim Steiner, director of Penn State University’s arboretum, and a science advisor to the ACF.

Paleontologist Jack Horner with a bird skeleton during a presentation at the Museo di Storia Naturale in Milan, Italy, in 2012

Another example of going backward in terms of evolution is paleontologist Jack Horner’s dino-chicken project, otherwise known as Chickenosaurus. As described in his and James Gorman’s 2009 book How to Build a Dinosaur: Extinction Doesn’t Have to Be Forever, Horner and his colleagues have been reverse-engineering characteristics in chickens.

“Birds are dinosaurs, so technically we’re making a dinosaur out of a dinosaur,” Horner, who served as the technical adviser for all of the Jurassic Park films, explained at the time of the book’s release. He added that he and his team hope to “awaken the dinosaur within.”

The process is a slow and gradual one, however. Advances so far include turning the beaks of chicken embryos back into dinosaur-like snouts by reverse, genetic engineering, and recreating dinosaur-like leg and foot anatomy in chicken embryos.

Horner believes that the work could lead to medical discoveries that may benefit humans, since learning what prompts and stops the growth of anatomical features could provide insights into serious human birth defects.

The dino-chicken project, even if fully successful, would not necessarily bring a particular species back from extinction. Paleontologists have not yet pinpointed what specific non-avian dinosaurs gave rise to modern birds.

One of the animal species that Wray believes could be brought back from extinction over the next decade is the woolly mammoth. Among those with that goal is George Church, a Harvard geneticist, and the Revive & Restore project.

“Church predicts he might be able to create an engineered elephant embryo that could give rise to an ‘unextinct’ mammoth in a couple of years,” Wray said, “but that’s just the embryo. It would take many more years after that to create a herd of animals successfully from those kinds of embryos.”

A de-extinction project is also underway in Europe to bring back giant wild cattle, known as aurochs, which went extinct in 1627. Rewilding Europe and the Taurus Foundation have established multiple breeding sites for the Taurus program, which involves crossbreeding Iberian and Podolian breeds of cattle in order to achieve mammals with auroch-like properties.

“The biggest misconception about de-extinction is that it is possible to bring extinct species back to life in identical form; it isn’t,” said Wray.

Aurochs depicted in a cave painting from Lascaux, France

Wray explained that there are always important differences between the extinct animal and the ones that scientists might be able to create in these animals’ images. With cloning, for example, the nucleus from a cell of the extinct animal is transferred to a living relative host’s egg cell to produce the new animal clone. But DNA is also stored in organelles called mitochondria, which sit outside of the cell’s nucleus in the cellular jelly.

“These don’t get transferred, and so the host egg cell provides the mitochondria for the clone that gets produced,” Wray said. “This could create only a small genetic difference, but either way, it’s no genetically identical copy of the original.”

The surrogate mothers that are used to bring lab-created fetuses to term could introduce hormonal, microbiotic, or other differences. Gene editing is also not an exact science, in terms of de-extinction goals, Wray said.

“It’s only select genetic changes from the genomes of the extinct animal that scientists will edit into the genomes of their closest living relatives in order to give them specific traits that are deemed important,” she said. “They’re not making 100 percent of the changes, and so they’re not really creating a hybrid between the extinct animal and its living relative.”

The other primary de-extinction technique, backbreeding, uses artificial selection techniques along the lines of the work to restore the American chestnut tree. “So the de-extinction process here is only ‘skin deep,’” Wray said, referring to how the new species may look like its predecessor, but is “not the real identical thing.”

Britt Wray

Undaunted by the present de-extinction limitations, Michael Archer and his team from the University of New South Wales and The Lazarus Project have been working to create a proxy for the gastric-brooding frog. The frog’s genus Rheobatrachus consisted of two species, both of which were classified as extinct in the mid-1980s.

The genus made headlines even before the die-out, as the frogs were the only ones known to have females that incubated their pre-juvenile young in their stomachs. When disturbed, the mothers would sometimes regurgitate their young in a single dramatic act of propulsive vomiting.

The upchucking did not lead to their extinction, though. Human introduction of a pathogenic fungi into the frog’s native range of eastern Australia did. Archer and his team have made progress in turning that seeming finality around.

“They’ve been able to clone DNA from the extinct frog in great-barred frog embryos, but those embryos haven’t yet developed successfully into tadpoles,” Wray said.

She added that Archer and his colleagues only have one chance a year to try to produce the embryos, due to the reproductive cycle of the great-barred host frogs. They plan to try again in 2018.

The gastric-brooding frog, now extinct, Rheobatrachus silus

Another animal in line for de-extinction is the passenger pigeon. Once endemic to North America, the pigeons were hunted extensively by both Native Americans and Europeans. Habitat loss also contributed to the ultimate demise of the birds, with the last wild one confirmed to have been shot in 1901. When a beloved passenger pigeon named “Martha” at the Cincinnati Zoo died in 1914, the entire species was declared extinct.

Ben Novak of Revive & Restore has been sequencing the passenger pigeon’s genome to study important aspects of the species’ ecological niche vital to its restoration. He and his colleagues estimate that engineered passenger pigeon proxies might be born around 2022.

Such research would appear to help fix problems that humans largely created, since our species contributed to the extinction of passenger pigeons and many of the other animals, including woolly mammoths.

Wray believes biotechnologies applied to de-extinction research should be utilized to help save threatened species, such as corals, bats, bees, and northern white rhinos. She believes that working to save these animals, before they actually go extinct, is where “the most ethical and beneficial application of the technology lies.”

She also thinks that de-extinction work could energize young students by showing them how science may be able to regenerate aspects of biodiversity.

“Young people mainly hear about the loss of precious ecosystems and the fact that they may never get to see a polar bear in the wild,” Wray said. “Perhaps de-extinction and its related technologies could make younger generations excited, rather than jaded, piquing their curiosity for what may be possible in their lifetimes. It’s about creating a hopeful narrative.”

She and others have serious concerns about de-extinction attempts, however.

Animal welfare is a major one. Wray said there is a lot of “animal failure involved in cloning processes, and some of the animals that do make it may end up in captivity for most, if not all, of their lives.”

The quest for necrofauna may also divert resources and attention from conservation programs for currently endangered species, but zoologist Philip Seddon of the University of Otago thinks that is a faulty argument.

“People have argued against de-extinction as pulling funding away from extant species conservation, but the counter to this is that those interested in funding high-tech approaches such as de-extinction are not likely to be interested in funding ongoing species conservation work, i.e. for every resurrected mammoth we would not have to fire a wildlife ranger,” he told Seeker.

“But, and this is a key issue, once resurrected species move out of the labs and into reserves they become the responsibility of cash-strapped conservation agencies, and unless more money enters the system, something has to drop off,” Seddon added.

It remains to be seen if these “reserves” could become the Jurassic Parks of the future, generating ample funds from members of the public hoping to see resurrected animals. Researchers may even patent their creations.

“Due to the high level of genetic modification that will be required to make many of the animals, they will not be seen as a product of nature in the eyes of the law, and therefore should be patentable,” Wray explained.

Read more at Seeker