Recently, the news of the last male Northern White Rhinoceros passing away sent the world into a now-routine tizzy about the need to ensure that animals aren’t endangered or worse, driven to extinction. We’ve seen, time and again, how this kind of social media activity fizzles out in no time without any actual measures being taken. It is no secret that we’ve done a terrible job at conservation. If you still need statistics, a total of 801 species have gone extinct since the emergence of humans. Species are disappearing at a rate of 1,000 to 10,000 times more than the Earth’s natural extinction rate, according to the World Wildlife Fund – certainly faster than what our conservation efforts can keep pace with. Which is why a certain section of the scientific community is turning its attention towards de-extinction.
Bringing back the dead
De-extinction, also known as resurrection biology, sounds like something right out of a fantasy world’s necromancy schools. Without putting a fantastic spin to it, it suffices to say de-extinction is the area of science that deals with bringing back species that have disappeared or similar species. Why do we say similar? To understand that, we need to understand the methods at play here. But first, should we bring extinct animals back?
The question has been asked time and again by concerned people of both scientific and non-scientific inclinations – wouldn’t bringing back extinct species interfere with nature? Wouldn’t it be akin to playing God? (that typically does not work out so well). The answer is mostly in the negative. That is because we have already interfered too much with negative consequences. We caused the extinction in the first place and it is logically imperative that we get behind efforts to bring them back. Which brings us to the important question – how?
Somatic Cell Nuclear Transfer (SCNT)
Cloning is one of biology’s most talked about areas. Cloning beings that are alive have already faced a copious amount of speculation on the ethics of the endeavour. You can imagine what the uninformed consensus about applying the same technology to dead species is. That hasn’t deterred path-breaking work in this area.
First things first – what we are going to talk about here isn’t really cloning. It is mainly a Somatic Cell Nuclear Transfer (SCNT) where one set of cells is coming from the preserved remains of an extinct species. One of the recent examples of this process comes with the de-extinction of the bucardo. The bucardo was a wild goat, the Pyrenean ibex, that was driven to extinction by hunters in the mountain range that divides France from Spain. After Celia, the last living bucardo passed away in an accident in the mountains, a team of Spanish and French scientists started working on bringing the species back from extinction. Led by José Folch, the team managed to inject the nuclei from Celia’s preserved cells to goat eggs that had been emptied of their own DNA, subsequently implanting those eggs into surrogate mothers. After 57 of these attempts, only 7 instances of pregnancy was achieved, out of which only one survived till delivery. The 4.5 pounds goat didn’t survive for long as she had a gigantic extra lobe in her lungs that made it impossible to breathe.
This was almost 15 years ago. The method involved has been improved to a vast extent and SCNT, in this manner, is way more reliable now. The technology is no longer a high-risk endeavour. Researchers are now able to induce adult animal cells to return to an embryo-like state. These cells can then be made to develop into any type of cell – including eggs or sperm – which can then be further manipulated to develop into full-fledged embryos.
In the early 1800s, nobody would have thought that the Passenger Pigeon, a species abundant enough to block out the sun when flocks flew by, would become extinct a hundred years down the line. Yet, decades of relentless hunting later, the last passenger pigeon would perish in captivity in 1914, at the Cincinnati Zoo.
Environmentalist and author Stewart Brand has led the effort to bring back the species through a project under Revive and Restore (revive&restore), an organisation that aims to apply new genetic technology to solve biodiversity problems. The project, dubbed the Great Passenger Pigeon Comeback, began in 2012. The process that they are following also sets the outline for bringing back quite a few other extinct bird species.
To begin with, the genomes of the Passenger Pigeon and the Band-Tailed pigeon, its closest living relative, are compared. While the genome for the Band-Tailed pigeon is readily available, that of the Passenger Pigeon has to be generated by comparing sequences from its remains. After the comparison, the areas where they aren’t same are identified. Primordial germ cells (PGCs) are extracted from a band-tailed pigeon which is then edited using CRISPR to write in the ‘passenger pigeon’ DNA. These edited PGCs are then injected into a rock pigeon where they migrate to the reproductive organs. After successful breeding, the first generation of passenger pigeons will be born all over again.
Currently, the project has successfully completed and sequenced the entire genome for the Band-tailed pigeon and have sequenced DNA from 37 passenger pigeons. Joined by the Center for Genome Architecture at Baylor College of Medicine in 2017, the project has begun to edit Domestic Rock Pigeon genome to test the feasibility of the method. The next step is to raise enough money for the germline transmission. The project aims to achieve de-extinction by 2020 and release a flock of 10,000 Passenger Pigeons into the wild by 2030.
While we’ve dealt with the moral question behind de-extinction, they are far-reaching biological and ecological implications of bringing back a species that does not exist out there in the wild anymore. The impact of the revived species, as an invading ‘alien’ species, with respect to the current balance in biodiversity, has been questioned significantly. Additionally, doubts have been raised about the ability to sustain the revived species. The first ones brought back to life would be raised by parents from a different species, which might interfere with their expected natural lifecycle or change it altogether. The biologists working on these projects have answers to these questions. Take the passenger pigeon for instance – most of its behaviour is encoded into its genes, thus nullifying the effect that being raised by other species might have on it.
On the other side, things look good. Bringing back a species like a passenger pigeon might actually go a long way in protecting the natural biodiversity in the region it originally dwelt in. Australia’s southern gastric-brooding frog possessed a unique ability to incubate its eggs in its stomach, effectively turning it into a uterus. This ability made it a medical marvel to be studied before it went extinct due to widespread fungicide abuse. Bringing back a species like this could help us gain an understanding of gastrointestinal enzymes and how we can control them. Even bringing back the Wooly Mammoth would restore the diversity of its original habitat to a great extent. The benefits of bringing back extinct species clearly outweigh the probable disadvantages. The important question is, once we bring them back, will we let them down again? Let’s hope not.