On Apr. 7, 2025, scientists at Colossal Biosciences announced the successful de-extinction of the dire wolf with the pups – Romulus and Remus, named after the mythological twins said to have been raised by a wolf. The dire wolf went extinct more than 10,000 years ago, and has been popularize in the television series ‘Game of Thrones.’

Dire wolves, though visually similar to today’s gray wolves and jackals, had a distinct genetic lineage. Unlike with the gray wolf and jackal, which can produce hybrid offspring with related species, there is no current data showing interbreeding between dire wolves and other canids.

The project began when an international team of more than fifty scientists examined 46 dire wolf remains for viable DNA and were able to recover 0.1% of the genome. The Colossal team subsequently examined the two most promising dire wolf samples, uncovering 55x more DNA to expand on the findings of the international team.

The team of computational biologists identified and edited more than 92 genes, and determined that these variants greatly contribute to the dire wolf’s size, muscle mass, craniofacial morphology, coat color and fur length. One of the core genes discovered by Colossal’s team of experts, was a dire wolf variant of a well-known gene found in canids. Ligand Dependent Nuclear Receptor Corepressor Like, otherwise known as LCORL, played a large role in determining the dire wolf’s increased stature.

LCORL encodes for a transcription factor—a key regulatory protein that controls the expression of hundreds of other genes related to body size and growth. Within the wolf genome, the LCORL protein binds more than 1200 times in order to control other genes. Still, despite its unique properties, this gene is not exclusive to wolves. Variants have also been associated with body size in many other living beings, including humans, pigs, horses, cattle and dogs.

The innovations stemming from Colossal’s research on wolf reproductive biology aren’t limited to wolves. During the dire wolf project, a novel mammalian cloning method was invented, with implications for numerous endangered species. Previously, mammalian cloning relied on tissue samples, often sourced invasively, which posed challenges for endangered species.

Romulus and Remus were born October 1, 2024, and for the first time in human history a once-eradicated species has been reestablished.