Did scientists make real dire wolves?

If you’re reading this, you’ve probably heard the news that scientists have “brought back” dire wolves through the power of genetic engineering. What does that mean though? Can we really “bring back” a species that went extinct? Are Romulus, Remus, and Khaleesi true dire wolves, or are they gray wolves with “dire wolf-like” traits? To answer these questions, let's look more closely at de-extinction and the specific approach taken by researchers at Colossal Biosciences.

Diving into the world of de-extinction

While the latest advances in technology have made the idea of reviving extinct animals seem more achievable, “de-extinction” is not as new of a field as you might think. Since the 1800s, people have been seeking to restore ecosystems by returning important species that have been wiped out. In most cases, that involved taking surviving members of a species from one region and re-establishing them in a place where they had gone extinct. However, some people, like Feliks Paweł Jarocki at the University of Warsaw, were already dreaming of re-creating species, like the aurochs, that had completely died out.

Before we knew much about DNA or genetic engineering, people started using traditional breeding methods to try to create replacements for the extinct aurochs in Europe and quagga in South Africa. However, advances in technology and genetics over the past couple decades have led to much more ambitious efforts to replicate or "resurrect" animals like woolly mammoths and dire wolves.

What makes a wolf a “dire” wolf?

So, what exactly is a dire wolf and how is it different from the wolves we have today?

Dire wolves were canids - like today’s wolves and coyotes- that went extinct about 10,000 years ago. Their fossils have been found across North and South America, along with a few in eastern Eurasia, and by examining these fossils, scientists have learned a decent amount about what they may have been like when they were alive.

For example, while the scientific name for dire wolf (Aenocyon dirus) literally translates to “terrible wolf”, their fossils tell us that they were actually not too much bigger than the largest gray wolves are today.

While dire wolves might not have been too much taller or heavier than today’s wolves, their skulls suggest that they did have much larger teeth and an incredibly strong bite force.¹ This would have helped them eat large animals, like the ancient camels and giant ground sloths that shared their territory. 

So, is a dire wolf just a slightly larger gray wolf with a more powerful bite?

Advances in technology have allowed us to learn a bit more about the evolutionary relationship between dire wolves and the wolves we have today. Scientists have managed to collect DNA from dire wolf skeletons, and by carefully piecing together the sequences of this ancient DNA, they’ve found that dire wolves and the gray wolves we have today went in different evolutionary directions over 4 million years ago.^2,3 This is likely the result of geographic isolation that prevented dire wolves from breeding with other species of canids.

So, have we really brought dire wolves back from extinction?

To get at this question, let’s take a closer look at what the scientists at Colossal Biosciences actually did. First, where did the DNA for Romulus, Remus, and Khaleesi come from?

Working with DNA from ancient organisms is really tricky because DNA breaks down over time. This means that it is incredibly difficult to piece together a complete genome for an animal that went extinct thousands of years ago. To get around this, scientists working on de-extinction projects tend to use DNA from modern relatives of extinct animals as a sort of foundation for genetic engineering.

In this case, the scientists at Colossal Biosciences chose to use gray wolf DNA since gray wolves share a decent amount of similarities with dire wolves. The scientists collected a blood sample from a live wolf, and they collected a certain type of cell from the blood that they could manipulate in the lab. They then used an approach called CRISPR to re-write the sequences of 14 genes in the DNA of those cells so they would more closely match the dire wolf versions of those genes.

One of the most notable changes was made in a gene called LCORL, which contains the instructions for a protein that helps control growth. Previous research found that larger dog breeds are missing part of the sequence for LCORL compared to smaller dog breeds,⁴ and the scientists at Colossal Biosciences noticed that dire wolves had a similar change relative to smaller species of wolves. By deleting part of the LCORL sequence from the gray wolf genome, the scientists were able to engineer animals that are the size of dire wolves. Changes in the other 13 genes resulted in other dire wolf traits like larger heads and white fur.

Once the scientists had cells that expressed the dire wolf versions of certain genes, they used a technique called somatic cell nuclear transfer to make engineered wolf embryos. The way somatic cell nuclear transfer works is you take the nucleus - the part of a cell with the DNA - from one cell, and you put that nucleus inside an egg cell that has had its nucleus removed. This creates an egg cell with a full set of DNA, which is able to develop into an embryo just like a fertilized egg would. Colossal Biosciences then used domestic dogs as surrogate mothers to carry the embryos to term and take care of the pups.

So, at the end of this complex process, we have pups that are larger than the average gray wolf pup and have different sequences for 14 genes relative to other gray wolves. Do these differences make them true dire wolves?

Not really.

Wolves have thousands of genes, and given that gray wolves and dire wolves went on separate evolutionary journeys for over 4 million years, rewriting a gray wolf genome to perfectly match that of a dire wolf would take a lot more than changing 14 genes. While Romulus, Remus, and Khaleesi may share some traits with extinct dire wolves, at the end of the day, it is much more accurate to say they are “dire wolf-like” gray wolves.