Is the once-extinct dire wolf back? | Explained

Colossal Biosciences "resurrects" dire wolves with genetic editing, sparking ethical and ecological concerns in conservation efforts.

The story so far: On April 7, a biotechnology company in Texas, U.S., named Colossal Biosciences announced that it had “resurrected” a dire wolf, a large predator that went extinct more than 12,000 years ago. The company’s claim that it had facilitated the birth of three dire wolf pups was met with a mix of wonder and delight. Videos of the baby wolves howling went viral, with the company calling their howls the first to be heard on earth in 10 millennia.

The total DNA content of an organism, called its genome, is important to understand its identity. The genome of a gray wolf consists of 2.447 billion base pairs. This means there are 2.447 billion positions in the DNA filled by one of the four nucleotides: adenine, thymine, cytosine, and guanine. The order in which these four nucleotides appear determines the genetic identity of an organism. In a preprint paper uploaded on April 11, Colossal Biosciences claimed that the genomes of the gray wolf (Canis lupus) and the dire wolf (Aenocyon dirus) are 99.94% identical, meaning 2.445 billion of the 2.447 billion base pairs were in the same places in the two genomes.

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This small difference is enormous in genetic terms. Humans and chimpanzees share about 98.77% of their DNA, yet no one would mistake one for the other. In the case of wolves, the 0.06% difference still corresponded to 1.47 million base pairs differing between the two species.

These differences are what make the two animals distinct. To create these ‘dire wolf’ pups, Colossal scientists edited the genome of a gray wolf and implanted embryos with the modified genome into surrogate dog mothers. While Colossal hasn’t revealed the exact nature of the changes its scientists made, it says on its website that it made “precise genetic edits at 20 loci across 14 genes” on the genome of a gray wolf to “recreate” the dire wolf. In other words, even if there were a few hundred individual edits across those 20 loci (or positions on the genome), the new animals probably contain 0.02% of the changes that would make them a true dire wolf. And this is an optimistic estimate. Put another way, the new wolf pups are far from being dire wolves.

The 20 locations where Colossal scientists edited the gray wolf genome all appear to be places that would result in cosmetic changes. For example, one of these regions is on a gene called LCORL, which is responsible for the dire wolves’ larger size. Other edits include genes involved in fur colour and density. Thus, Colossal Biosciences can be said to have made gray wolves that look like dire wolves.

While the nature and magnitude of the genetic differences already undermine Colossal’s claims, a 2021 study published in Nature raised a more fundamental issue. The study suggested that despite genetic similarities, dire wolves may not be true wolves at all, but rather a distinct canid lineage that diverged long before modern wolves evolved. This study prompted scientists to reclassify dire wolves, and their species name changed from Canis dirus to Aenocyon dirus. This means dire wolves’ behaviour, social structure, and ecological roles are likely different from that of modern wolves.