“De-extincted” Dire Wolf Pups Have a Few Genetic Tweaks – That’s It

The images of “de-extincted” fuzzy white dog-wolf pups festooning the media this week accompany reports that are so hyped that the technical feat is hidden in the hoopla.

Claimed the company, Colossal Biosciences:

“On October 1, 2024, for the first time in human history, Colossal successfully restored a once-eradicated species through the science of de-extinction. After a 10,000+ year absence, our team is proud to return the dire wolf to its rightful place in the ecosystem. Colossal’s innovations in science, technology and conservation made it possible to accomplish something that’s never been done before: the revival of a species from its longstanding population of zero.”

The statement isn’t grammatically correct – had their team really been absent for 10,000 years? And no, they haven’t restored a species, they tweaked a few genes in a modern gray wolf’s genome.

It’s little wonder that the cover of Time featured a red bar blaring EXTINCT over a photo of the adorable pups.

Fortunately, media outlets that interviewed geneticists quickly put out the hype fire.

“This kind of hype is toxic and harmful to science, including public trust. Some people, apparently even top U.S. administration officials, now believe the dire wolves are back. The three gray wolves with fifteen gene edits making them genetically a smidge more like dire wolves are not a de-extinction event,” wrote my friend Paul Knoepfler, a noted stem cell researcher, in his blog The Niche. The pups are an early contender for Dr. Knoepfler’s annual Screamers Science Hype Award.  

The Dire Wolf in Life and Song

The images of puppies Remus and Romulus (named after mythical twins raised by a she-wolf) brought back memories of visiting our daughter Sarah when she lived with an enormous white wolf, Daria. Sarah’s partner had rescued the animal, a full white-colored gray wolf, from the gang of bikers who’d taken her from the Canadian wilderness. Daria became a loving pet, but her howling did sometimes unnerve Sarah.

When we visited it was disconcerting to awaken to find Daria stretched out between us. The magnificent white animal blinked, then loped off the bed to explore a setting more intriguing than slumbering humans.

Most of the time, Daria didn’t seem very wolf-like. But she howled at the moon, occasionally attacked her canine housemate, and once went after a neighbor’s tiny yapping canine, in the small mountain town in northern California.

The 1970 Grateful Dead tune “Dire Wolf” captures the enormity of the extinct canid. Lyricist Robert Hunter wrote, reportedly after watching The Hound of the Baskervilles:

“When I awoke, the dire wolf

600 pounds of sin

Was grinning at my window

All I said was, ‘Come on in’

Don’t murder me

I beg of you, don’t murder me

Please, don’t murder me.”

The dire wolf had massive jaws, huge teeth, a thick skull and the striking white coat. At maturity, the animal weighed about 150 pounds and stood up to six feet tall.

Despite its phenotype – aka appearance – the dire wolf was not a close relative of dogs today, not even mixes like Daria. The animal split from other canids in North America about 5.7 million years ago – evolution branches, it isn’t a straight line as memes depict. And genome sequences of modern canids do not indicate that dire wolves mated with gray wolves or coyotes.

DNA sequence evidence suggests that dire wolves evolved in North America in isolation during the Pleistocene, 13,000 to 50,000 years ago. They weren’t the direct ancestors of gray wolves, coyotes, and dholes (a canid from southeast Asia), which came from Eurasia to North America fairly recently, according to this report in Nature.

A Wolf in an Older Wolf’s Clothing?

The company website claims that “these are actual, giant, genetically accurate, scientifically verified dire wolves walking the Earth again.”

What does “scientifically verified” mean? Is Fred Flintstone heading up a committee that Elon Musk hasn’t yet dismantled?

The science, as far as I can tell, does appear to be a logical wedding of existing biotechnologies.

Remus and Romulus and their younger sister Khaleesi, named for a Game of Thrones character, began with DNA extracted from a 13,000-year-old tooth found in Ohio and a 72,000-year-old inner ear bone from Idaho, both from dire wolves.

Next, the investigators identified gene variants that differ in DNA sequence between the extinct and modern wolves – encoding traits like muscle mass, whisker length, skull shape, coat color, and vocalizations. They carefully considered genes and traits to select. For example, rather than using three genes for albinism, which could also bring albinism and deafness, the researchers chose to use the same pigment gene that makes Daria white.

Then the researchers used CRISPR to alter 20 sites in the genome of a white blood cell from a living gray wolf to recreate selected traits from the extinct wolf – a stronger jaw muscle, light color, size, and a different bone used in reproductive behavior. The 20 sites that were edited correspond to 14 genes. One gene had two edits, so that’s alteration to 15 protein-encoding genes total. The remainder, I assume, are regulatory DNA sequences.  

Next, the researchers transferred the tweaked genome with the essence of ancient genes into an egg from a dog in which the half-load of chromosomes had been destroyed. In other words, cloning.

After a few rounds of cell division, tiny embryos were transferred to other canines that served as surrogates. And two months later, Remus and Romulus were born. At three months, they already weigh 80 pounds and stand four feet tall.

Perspective

Select journalists were allowed to view Remus and Romulus, to avoid accusations of AI-generated images.  

But let’s put the genetic modification into perspective.

1. A dire wolf’s genome is 2.5 million DNA base pairs, encoding about 19,000 genes.
2. The researchers made 20 genome edits encompassing 14 genes.

Here’s a literary analogy. The Hound of the Baskervilles, by Arthur Conan Doyle, is 62,297 words. The 20 edits made to the canine genome correspond to about 50 single-letter typos in the 250-page novel.

That’s hardly creating an “officially resurrected … prehistoric predator.” Who would such an official be? RFK Jr?

Fortunately, geneticists soon spoke up.

The Evolution of Science Hype

I’ve been covering biotechnology since the 1980s. Back in the day, news of an upcoming peer-reviewed report published in a science or medical journal was announced to journalists via news (aka press) releases, with an embargo. That gave us time for background research, especially noting what’s left out – such as the details of a genetic manipulation.

COVID shifted the news trajectory to not-yet-peer-reviewed preprints, as the word “research” shifted from something experts do to something everyone does.   

The partial dire wolf’s debut went directly to the media, which at first echoed the language of the company website.

A “remarkable scientific breakthrough” (ABC News)

“The dire wolf, which went extinct 12,500 years ago, revived by biotech company” (CBS News)

“The Wonder and Controversy of Bringing Back the Dire Wolf from Extinction” (Venture Beat)

Even politicians, some known to identify as scientists, weighed in.

The work is “a thrilling new era of scientific wonder,” proclaimed Interior Secretary Doug Murgum on X, perhaps unaware of efforts to bring back the woolly mammoth, carrier pigeon, and heath hen. (DNA Science has covered resurrecting Przewalskis horse and extinct flowers.) Colossal creates hybrids too – they introduced their fuzzy, mammoth-like mice a few weeks ago.

A few outlets voiced skepticism and used qualifiers from the outset, such as CNN’s “Scientists say they have resurrected the dire wolf” and the AP’s “Scientists engineer wolves to look like extinct dire wolf.”

CODA

Why “bring back” the dire wolf?

The Colossal website provides a noble perspective: the widely-cited prediction that half of today’s species will be extinct by 2050. Let’s take the dire wolf off the list! The preprint article considers “where today’s dire wolves will live…” I’m not sure that extinction prevention, or delay, justifies the $10 billion valuation of the pups.

Even if the genetic tweaks weren’t so minor, the pups will grow up in a world in which dire wolves are no longer around. Imagine Fred Flintstone finding himself plopped down in midtown Manhattan.

Yet even if the introduced traits drive speciation, the primary force of evolutionary change, natural selection, requires complex factors from the environment – and time. Experiments with single-celled organisms or animals with short lifespans, like fruit flies, can glimpse evolutionary change, but creating a new species – especially one as complex as a mammal – can’t happen in a lab.

Ian Malcolm, mathematician in the original Jurassic Park film, captured well the potential consequences of mixing and matching genomes:

“Your scientists were so preoccupied with whether they could, they didn’t stop to think if they should.”