> Colossal’s dire wolf work took a less invasive approach, isolating cells not from a tissue sample of a donor gray wolf, but from its blood. The cells they selected are known as endothelial progenitor cells (EPCs), which form the lining of blood vessels. The scientists then rewrote the 14 key genes in the cell’s nucleus to match those of the dire wolf; no ancient dire wolf DNA was actually spliced into the gray wolf’s genome. The edited nucleus was then transferred into a denucleated ovum. The scientists produced 45 engineered ova, which were allowed to develop into embryos in the lab. Those embryos were inserted into the wombs of two surrogate hound mixes, chosen mostly for their overall health and, not insignificantly, their size, since they’d be giving birth to large pups. In each mother, one embryo took hold and proceeded to a full-term pregnancy. (No dogs experienced a miscarriage or stillbirth.) On Oct. 1, 2024, the surrogates birthed Romulus and Remus. A few months later, Colossal repeated the procedure with another clutch of embryos and another surrogate mother. On Jan. 30, 2025, that dog gave birth to Khaleesi.

The process seems to have dictated this. They needed an easy surrogate, a dog, and wolves required no need of introducing anything new into the genome, it's "just" reactivating what is already there.

Haven’t read full article either. But dogs have an incredibly well studied genome and are generally incredibly well understood. And due to cloning efforts, performing implantation of lab grown embryos is established protocol. Wolves are also well studied and understood, so even tho dire wolves aren’t super closely related, the dog baseline is a great control.

This would be a lot harder to do with an extinct species we don’t know well.

From the article, it looks like they have multiple teams working on multipe animals at the same time. But the dodo team is going slower than the mammoth and the wolf :

> Keyte added that her team was still a long way from bringing back the dodo. For one thing, the methods for growing and manipulating the embryonic precursors of avian sperm and eggs in a lab setting have been developed for only two birds: the chicken and, recently, the goose. Keyte said, “It’s been almost twenty years since culture conditions for the chicken were established, and those culture conditions have not worked for other bird species, even ones that are really closely related, like quail.” She added that, despite the dearth of related research, her team was getting better at growing the sperm-and-egg precursors in birds: “We’ve gotten to the point where we feel like we can start doing some migration assays”—a technique for studying how the cells in an early embryo begin to differentiate. Once the researchers got the basic method for growing bird cells down, they could use the technology not just to develop a dodo but also to help replenish populations of endangered birds. The team had already identified some species that could use the help.

I'm guessing it's a mixture of practical concerns and something that captures the imagination of investors.

We have robust cloning protocols for dogs. For some reason dogs are really amenable to cloning.

Birds are more difficult to clone than mammals. I don't think we've been able to clone one yet.

I hope to see a passenger pigeon one day though.

Searched for this. Passenger Pigeons are the #1 species I want resurrected.

I would guess that it has to do with much more available genetic information on dogs and more existing CRISPR work with them. However, I do not know if these wolves will give us a lot of information.

That said, the dodo is on Colossal's list of projects, along with the wooly mammoth and the thylacine (Tasmanian tiger).

My guess is that it is indeed because they're charismatic megafauna.

Because Game of Thrones popularized the idea of a dire wolf as an exceedingly rare protector of children, which helps them persuade investors that there is a viable luxury market for this product. They named one “Khaleesi”, so it’s not a coincidental reference.

House of Stark will still be happy to hear their heraldic animal is back.

But yeah, clever marketing by this company.

GRRM also helped fund the project