Colossal Biosciences Inc. is an American biotechnology and genetic engineering company working to de-extinct the woolly mammoth, the Tasmanian tiger, the northern white rhinoceros, and the dodo bird.

[12][13] In a 2008 interview with The New York Times, George Church first expressed his interest in engineering a hybrid Asian elephant-mammoth by sequencing the woolly mammoth genome.

[4] In 2012, Church was part of a team that pioneered the CRISPR-Cas9 gene editing tool, through which the potential for altering genetic code to engineer the envisioned “mammophant" surfaced.

[22] The company's genomic modeling software development could potentially bring forth advancements in disease treatment, multiplexed genetic engineering, synthetic biology, and biotechnology.

[15][20] Colossal recruited mammoth and modern elephant experts Michael Hofreiter and Fritz Vollrath, as well as bioethicists R. Alta Charo and S. Matthew Liao for their consultation.

[4] Other scientific advisory board members include: Carolyn Bertozzi, Austin Gallagher, Kenneth Lacovara, Helen Hobbs, David Haussler, Elazar Edelman, Joseph DeSimone, Erez Lieberman Aiden, Christopher E. Mason, and Doris Taylor.

[26] The same month, Colossal launched its Conservation Advisory Board, which includes Forrest Galante, Iain Douglas-Hamilton, Mead Treadwell, and Aurelia Skipwith as its members.

[4] Key mammoth genealogical traits include: a 10-centimeter layer of insulating fat, five different types of shaggy hair, and smaller ears to help the hybrid tolerate cold weather.

[37] Colossal's lab will pair CRISPR/Cas9 with other DNA-editing enzymes, such as integrases, recombinases, and deaminases, to splice woolly mammoth genes into the Asian elephant.

[22] The company plans on sequencing both elephant and mammoth samples in order to identify key genes in both species to promote population diversification.

[41] Colossal plans to reintroduce the thylacine proxy to selected areas in Tasmania and broader Australia and claims that, by doing so, this will re-balance ecosystems that have suffered biodiversity loss and degradation since the species disappeared.

This marks “the most complete ancient genome of any species known to date” and provides a full DNA blueprint to potentially bring back the Tasmanian tiger.

[49][50] Three months later, in January 2025, the company sequenced the complete genome of the Tasmanian tiger;[51] Colossal also made a prototype for an artificial uterus and used that to culture fertilized single-cell marsupial embryos to over halfway through pregnancy.

[54] Colossal has also done genetic research for species such as the Irish elk, great auk, bluebuck, ground sloth, moas, and woolly rhinoceros, with the intent to potentially revive them in the future.

Under this collaboration, the organizations will work to restore “critical ecosystems through invasive species removal, revegetation, and community awareness efforts.”[63] Additionally, Colossal will also focus on the rewilding of the dodo bird as well as the genetic rescue of the pink pigeon.

The Colossal Biovault collects tissue samples of endangered species in hopes to allow cell lines to become accessible and stored in domestic partner facilities.

[70] In 2022, Colossal was listed as one of the World Economic Forum's Technology Pioneers and was named Genomics Innovation of the Year by the BioTech Breakthrough Awards.