Biotech Is Trying to Resurrect Extinct Species. Here's Why - and the Challenges We Face.

Sam Westreich, PhD

There’s more reasons to create Jurassic Park than for the tourists.
Trust me, we’re not trying to restore a wooly mammoth for the ivory.Photo by Christopher Alvarenga on Unsplash

Long before we discovered genetics, we’ve always been fascinated with the idea of extinct species. We’ve come across their bones, tried to reconstruct how these creatures looked, and written stories about what they would be like if they returned to life.

Most of us think of Jurassic Park, the bestselling novel by Michael Crichton that has spawned a whole series of blockbuster movies. Bringing back dinosaurs! What could go wrong? (As the movies teach us, pretty much everything goes wrong, about forty minutes into the flick.)

Even before Jurassic Park, however, we dreamed of discovering ancient species. In 1871, Jules Verne wrote Journey to the Center of the Earth, where his intrepid explorers discover living relatives of prehistoric creatures still thriving in caverns far below the surface.

But these aren’t just the dreams of science fiction writers. A number of companies and groups, most notably Colossal Biosciences, are working to try and bring extinct species back to life — for real.

Wooly mammoths. Thylacines (more commonly known as the Tasmanian Tiger). Why do it?

Is this just hubris, mankind trying to prove that even extinction is no bar to our call? Or is there an additional benefit?

Let’s look at how this process works, and what payoffs we may realize from bringing back an extinct species.

It takes more than dinosaur DNA from an amber-trapped mosquito

First, we have to understand that, while the Jurassic Park films made for great entertainment, they are not an accurate primer on the genetics of restoring an extinct species.

First, we need to obtain the DNA of the extinct species. Colossal Biosciences is targeting the wooly mammoth and the thylacine because these animals went extinct very recently, in evolutionary terms. Most of the wooly mammoths died out around 10,500 years ago, at the end of the last ice age. Some dwarf species held out until around 4,000 years ago, but their genetics show they were destined for extinction and were struggling due to inbreeding. The thylacine didn’t go extinct until 1936, when the last specimen died in captivity.

DNA has a half-life of around 521 years. The half-life is how long, on average, it takes for half of a substance to decay/degrade. If you have a piece of DNA, about half of the nucleotide bonds (the rungs of the ladder) would be broken and unreadable after 5 centuries.

This breakdown is multiplicative; after 1,000 years, only about a quarter of the DNA is intact. 2,000 years, and only around 6% of the DNA is intact. 4,000 years, and we’re looking at only 0.02% of the DNA still being intact. That’s practically nothing.

This means that 65-million-year-old DNA is not going to have any readable information. It’ll just be random degraded bases. Even “preserved in amber” cannot keep DNA intact for millions of years.

No dinosaurs are going to be restored from found genetic material any time soon — because that genetic material simply doesn’t exist. There’s no more dino DNA on Earth.

Even after we get the DNA, we can’t just pop a wooly mammoth out of nowhere. We need a close relative of that extinct species, one that can be our starting base for modifications.

After all, imagine that you created an egg in a lab with the wooly mammoth DNA. You’ll need a womb to grow that egg in, which means you need a closely related live species.

Making matters even more complex is the fact that DNA is not the only component to growing a mammoth. We get all sorts of developmental cues and signals from our parent as we develop in the womb. Even if a baby animal is born with wooly mammoth DNA, it may not be the same as a “true” mammoth, because it received fetal inputs from a modern elephant.

Colossal has disclosed that they plan to use an African elephant as the surrogate mother to their gene-edited faux-mammoth embryo. African elephants are larger and less endangered than the Asian elephant (which is technically the closest ancestor to the mammoth), making it slightly easier from a logistics standpoint.

But why m̶a̶l̶e̶ ̶m̶o̶d̶e̶l̶s̶ wooly mammoths?

Colossal isn’t just planning to bring back wooly mammoths to put them in a zoo for people to gawk at. There are two reasons that they discuss:

  1. Re-establishing an ecosystem in the tundra to better support carbon absorption and storage, helping to reverse global warming.
  2. A proof of concept to demonstrate that the extinct species revival approach is valid.

The first reason is the one that’s going to be touted in press conferences and releases. “Look, we’re helping to save the planet! We’re going to fix some of the manmade issues that are plaguing society through the ability of this keystone species to terraform its environment!”

(How would wooly mammoths help reduce global warming? Colossal says that mammoths would graze down forests and wetlands, allowing them to be replaced by grassland that can better sequester carbon and won’t heat up as much, preventing the release of stored underground carbon dioxide.)

Would woolly mammoths help bring back grasslands and reduce global warming? Maybe, although perhaps not to the degree that Colossal claims. The theory is being tested in smaller parks, but it’s not yet known just how many mammoths would be needed, or how much territory would need to be ceded to them in order to see a noticeable effect on preserving stored carbon.

But the bigger goal is the second one, that proof-of-concept. There are plenty of other creatures that could be brought back:

  • Passenger pigeons
  • Dodo bird
  • Elephant bird
  • Moa
  • Eastern cougar

This could also potentially help many other species that are currently endangered and at acute risk of going extinct in the next few years.

Even broader than that, however? This opens up additional proof for genetic engineering.

If we can make these edits in mammoths, we can learn about best practices. The end goal would always be humans; there are no currently approved genetic engineering interventions for any human diseases. Showing that they can successfully edit the genome of an elephant, transforming it into something approximating a mammoth, would make Colossal a valuable partner for a company looking to introduce CRISPR-driven changes in humans.

The checklist for bringing back an extinct species

Put it together, and bringing back an extinct species requires all of the following:

  1. Enough preserved DNA to be able to create a list of the specific mutations unique to the species.
  2. A closely related ancestor that can donate the starting eggs/sperm to be modified.
  3. Custom designed CRISPR interventions for each of the mutations you’ll need to add to make this species.
  4. Live females of the closely related species that can be the surrogate mother for the implanted, modified embryos.

Even with all these ingredients, it’s going to be a lot of work to get a viable embryo. Colossal lists more than 50 different mutations that will need to be introduced into the elephant embryos in order to simply restore the improved cold resistance of the mammoth.

All of these will need to be done to one cell. You have to take one singular egg cell and get ALL of these mutations added to it.

And then you’ll have to do it again, and again, and again. You can’t resurrect an entire species with a single individual; you’ll need enough revived individuals to establish a stable breeding population.

It’s going to be a lot of work, and it’s going to have a lot of failures. (Imagine that you get 49 mutations successfully edited — and then the 50th has off-target effects and leads to a nonviable embryo. Time to start over…)

We’ll have to wait and see whether Colossal is able to succeed.


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A microbiome scientist working at a tech startup in Silicon Valley, Sam Westreich provides insights into science and technology, exploring the strangest areas of biology, science, and biotechnology.

Mountain View, CA

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