Romulus, Remus, and Khaleesi facts for kids

Romulus and Remus are two genetically modified grey wolves (Canis lupus) created by Colossal Biosciences on October 1, 2024, with the goal of replicating the phenotype of the extinct dire wolf (Aenocyon dirus). Along with a female wolf named Khaleesi born later on January 30, 2025, Colossal claims the two males represent the first living examples of the species since its extinction approximately 10,000 years ago. As dire wolves belonged to a completely different genus, Aenocyon, Romulus, Remus, and Khaleesi are in fact genetically-engineered grey wolves.

Scientists rewrote 14 key genes in gray wolf EPC cells to express 20 dire wolf traits, meaning that "no ancient dire wolf DNA was actually spliced into the gray wolf's genome." The public announcement of their birth in April 2025 was subject to significant public attention.

Genesis

The creation of these gray wolves that are dubbed as "revived" dire wolves involved analyzing ancient DNA samples from two sources: a 13,000-year-old tooth discovered at Sheriden Cave, an Ice Age archaeological site in Wyandot County, northwestern Ohio, and a 72,000-year-old ear bone found in American Falls, Idaho. Colossal Biosciences's scientists stated that rather than directly inserting ancient DNA into modern animals, that they had identified approximately twenty genetic modifications across fourteen genes that differentiate dire wolves from modern gray wolves.

The scientific team isolated endothelial progenitor cells (EPCs) from gray wolf blood samples, then used CRISPR gene editing to modify 14 genes to express 20 traits which the company claims are found in dire wolves, including a larger body size, wider head, and white coat color. These modified nuclei were transferred into denucleated ova, which developed into embryos in laboratory conditions. From 45 engineered ova, three viable embryos were successfully implanted in surrogate mother dogs.

The surrogate mothers were selected domestic dog mixes chosen for their general health and size sufficient to accommodate the larger dire wolf pups. One particular surrogate mother, a domestic dog named Skyla, played a crucial role in the project. The pregnancies were continuously monitored with weekly ultrasounds, and all three births occurred via planned caesarean section to minimize complications.

Characteristics and growth

Born on October 1, 2024, Romulus and Remus are housed in a secured 2,000-acre (810 ha) ecological preserve within the United States surrounded by 10-foot (3.0 m) fencing, at an undisclosed location to protect them from disturbance. The facility includes a smaller 6-acre (2.4 ha) area containing a veterinary clinic, extreme weather shelter, and natural dens. They receive around-the-clock veterinary supervision. Romulus and Remus were named after the legendary twin brothers who founded Rome, and in Roman mythology had been suckled by a she-wolf as infants. As pups, a picture was taken of them resting on the original Iron Throne prop from Game of Thrones.

Their diet consists of deer, beef, and horse meat, supplemented with organ meats and specialized nutritional supplements. Initially fed pureed meat after weaning, they now receive whole portions that allow them to engage in natural tearing behaviors. The wolves have not been provided with live prey, though staff note they have not observed any interactions with small wildlife that may enter their enclosure.

Their genetic modifications resulted in several key physical differences from gray wolves, including a white coat coloration and distinctive vocalizations, particularly bearing unique howling patterns. Morphologically, the wolves have a larger overall body size with a more "powerful" shoulder structure, wider head shape, larger teeth and jaws, and more muscular legs. Behaviorally, the wolves exhibited natural wolf tendencies from birth, including early howling (beginning at approximately two weeks of age), stalking and hunting behaviors, and a natural wariness around humans. Unlike domesticated canines, they maintain distance from people, including their handlers, and display characteristic wolf retreat behaviors when approached.

Based on unreviewed genetic research, Colossal claims that dire wolves would have had a pale coat coloration. The pups' white coat results from a coat coloration gene expressed in dogs, chosen as a replacement for the purported original gene, which carries "a risk of blindness and deafness".

By six months of age, the male wolves measured nearly four feet (~122 cm) in length and weighed approximately 36.3 kg (80 lb) each. They are projected to reach six feet (~183 cm) in length and 68 kg (150 lb) at full maturity.

Their sister Khaleesi was born on January 30, 2025. She was named in homage to the Game of Thrones character Daenerys Targaryen. The three wolves are maintained as a small pack.

Limitations

While the wolves receive comprehensive care, their living situation presents limitations compared to natural wolf habitats. Their restricted territory and small pack size do not replicate natural wolf social structures or range needs. Furthermore, the specialized hunting adaptations of dire wolves—believed to have targeted ice age megafauna such as Columbian mammoth, prehistoric bison such as the giant bison, and Bison antiquus, Camelops, dwarf pronghorn, giant ground sloths such as the Megalonyx, and Harlan's ground sloth, American mastodon and wild horses such as the Mexican horse, western horse, and Hagerman horse—cannot be fulfilled in their current environment.

See also

In Spanish: Rómulo, Remo y Khaleesi para niños

• List of resurrected species
• Woolly mouse