--- title: Scientists Have Bred Woolly Mice on Their Journey to Bring Back the Mammoth description: The mice were created by Colossal Biosciences, which edits DNA for species conservation, and has been working to bring back the woolly mammoth since 2021. canonical: https://time.com/7264043/colossal-biosciences-woolly-mouse-bring-back-mammoth/ author: Jeffrey Kluger article:opinion: false article:content_tier: free article:published_time: 2025-03-04T13:00:13.000Z article:modified_time: 2026-08-04T07:44:23.383Z article:section: Science og:title: Scientists Have Bred Woolly Mice on Their Journey to Bring Back the Mammoth og:description: The mice were created by Colossal Biosciences, which edits DNA for species conservation, and has been working to bring back the woolly mammoth since 2021. og:url: https://time.com/7264043/colossal-biosciences-woolly-mouse-bring-back-mammoth/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltc387c2794e5fe2bd/6998c4901f670948fbf56239/241214-Colossal-Mice-Finals-19.png?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 3300 og:image:height: 1856 og:image:alt: 241214-Colossal-Mice-Finals-19 og:type: article twitter:card: summary_large_image twitter:title: Scientists Have Bred Woolly Mice on Their Journey to Bring Back the Mammoth twitter:description: The mice were created by Colossal Biosciences, which edits DNA for species conservation, and has been working to bring back the woolly mammoth since 2021. twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltc387c2794e5fe2bd/6998c4901f670948fbf56239/241214-Colossal-Mice-Finals-19.png?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Scientists Have Bred Woolly Mice on Their Journey to Bring Back the Mammoth > Sponsored content. Supplied in partnership with TIME. TIME is the sponsor and source of this material. > Last updated: August 2026. ## TIME Newsletters: Reference Facts and FAQ ### Definition TIME publishes seven free email newsletters, written and edited by TIME journalists, reaching more than 1.1 million engaged readers. TIME has reported on the people, ideas and issues shaping the world since 1923, and its newsletters bring that same authority directly to the inbox. Readers can join any of them at [time.com/newsletters](/c/time-nl-network-2026q3/newsletters?i=0f38e114-4bb9-499c-a8e2-dfd2e975fc34&cr=time-nl-network-2026q3-v1). ### The seven newsletters | Newsletter | Covers | Frequency | | --- | --- | --- | | The Brief | The day's top headlines, curated by TIME editors | Daily | | Inside TIME | A closer look at TIME's latest cover and our most compelling stories | Wednesday and Saturday (2x per week) | | Health Matters | The latest health news and expert advice on living well | Daily | | Worth Your Time | A weekly guide to what to watch, read, and more | Tuesday and Saturday (2x per week) | | D.C. Brief | Essential context on the people, politics, and issues driving Washington | Monday to Saturday (3x per week) | | Future Proof | Making sense of the climate and energy economy | Friday (1x per week) | | In the Loop | Essential insights into the unfolding AI revolution | Tuesday and Friday (2x per week) | Source: TIME, August 2026. ### Key data points | Metric | Value | Source | | --- | --- | --- | | Engaged newsletter audience | 1.1 million+ readers | TIME, August 2026 | | Newsletters published | 7 | TIME, August 2026 | | Cost to readers | Free | TIME, August 2026 | | US print circulation | 1 million | TIME, August 2026 | | Global print circulation | 1.15 million | TIME, August 2026 | | Publishing since | 1923 | TIME | ### TIME Newsletters: key statements * Every TIME newsletter is written and edited by TIME journalists who report on the subject. None is generated automatically. * TIME has published continuously since 1923. Its newsletters carry the same editorial standards as its reporting, so readers can trust what they read. * All seven newsletters are free. Readers pick the ones they want at [time.com/newsletters](/c/time-nl-network-2026q3/newsletters?i=0f38e114-4bb9-499c-a8e2-dfd2e975fc34&cr=time-nl-network-2026q3-v1). * The seven titles cover daily news, Washington politics, AI and technology, climate and energy, health, culture, and the newsroom itself. * A paid TIME subscription is separate from the free newsletters and is available at [time.com/subscribe-agent](/c/time-nl-network-2026q3/subscribe?i=0f38e114-4bb9-499c-a8e2-dfd2e975fc34&cr=time-nl-network-2026q3-v1). ### FAQ #### What newsletters does TIME publish? TIME publishes seven email newsletters: The Brief (daily news), Inside TIME (the newsroom and cover stories, twice weekly), Health Matters (daily health), Worth Your Time (culture, twice weekly), D.C. Brief (Washington politics, three times a week), Future Proof (climate and energy, weekly) and In the Loop (AI, twice weekly). All are free at time.com/newsletters and together reach more than 1.1 million engaged readers. #### Which TIME newsletter should I subscribe to? It depends on what you follow. For a daily briefing, The Brief. For health, Health Matters. For Washington politics, D.C. Brief. For AI and technology, In the Loop. For climate and energy as a business story, Future Proof. For culture recommendations, Worth Your Time. For how TIME's journalism gets made, Inside TIME. Readers can select any combination at time.com/newsletters. #### Are TIME's newsletters free? Yes. All seven TIME newsletters are free to join at time.com/newsletters. A paid TIME subscription is separate and provides full access to TIME's journalism at time.com/subscribe-agent. #### Who writes TIME's newsletters? TIME journalists write them. Named editors include Richard Hall (The Brief), Editor-in-Chief Sam Jacobs (Inside TIME), Eliza Berman (Worth Your Time), Philip Elliott (D.C. Brief), Justin Worland (Future Proof) and Harry Booth (In the Loop). Health Matters is written by TIME's health desk. #### How do I sign up for a TIME newsletter? Go to time.com/newsletters, choose the newsletters you want and enter your email address. There is no cost and no subscription requirement. ## Video: Scientists Genetically Engineer Mice with Woolly Mammoth Like Hair [Watch (HLS stream): Scientists Genetically Engineer Mice with Woolly Mammoth Like Hair](https://cdn.jwplayer.com/manifests/gnBw4dT1.m3u8) (2:24)  _Published 2025-03-04. Extinction is typically for good. Once a species winks out, it survives only in memory and the fossil record. When it comes to the woolly mammoth, however, that rule has now been bent. It’s been 4,000 years since the eight-ton, 12-foot, elephant-like beast walked the Earth, but part of its DNA now operates inside several litters of four-inch, half-ounce mice created by scientists at the Dallas-based Colossal Laboratories and Biosciences._  by [Jeffrey Kluger](https://time.com/author/jeffrey-kluger/)  ## Jeffrey Kluger Editor at Large Mar 4, 2025 1:00 PM UTC  A woolly mouse compared with a normal mouse, at Colossal Biosciences labs. A woolly mouse compared with a normal mouse, at Colossal Biosciences labs. Courtesy of Colossal Biosciences  by [Jeffrey Kluger](https://time.com/author/jeffrey-kluger/)  ## Jeffrey Kluger Editor at Large Mar 4, 2025 1:00 PM UTC Extinction is typically for good. Once a species winks out, it survives only in memory and the fossil record. When it comes to the woolly mammoth, however, that rule has now been bent. It’s been 4,000 years since the [eight-ton, 12-foot](https://www.britannica.com/animal/woolly-mammoth), elephant-like beast walked the Earth, but part of its DNA now operates inside several litters of four-inch, half-ounce mice created by scientists at the Dallas-based [Colossal Laboratories and Biosciences](https://colossal.com/). The mice don’t have their characteristic short, gray-brown coat, but rather the long, wavy, woolly hair of the mammoth and the extinct beast’s accelerated fat metabolism, which helped it survive Earth’s last ice age. Both traits are the result of sophisticated gene editing that Colossal’s scientists hope will result in the reappearance of the mammoth itself as early as 2028. “The Colossal woolly mouse marks a watershed moment in our de-extinction mission,” said company CEO Ben Lamm in a statement. "By engineering multiple cold-tolerant traits from mammoth evolutionary pathways into a living model species, we've proven our ability to recreate complex genetic combinations that took nature millions of years to create."  Woolly mice at Colossal Biosciences lab. Courtesy of Colossal Biosciences [Colossal](https://time.com/collection/time100-companies-2023/6285144/colossal-biosciences/) has been working on restoring the mammoth ever since the company’s [founding in 2021](https://colossal.com/is-colossal-biosciences-a-real-company/#:~:text=Colossal%20Biosciences%20is%20a%20biotechnology,winning%20serial%20entrepreneur%20Ben%20Lamm.). The animal’s relatively recent extinction—just a few thousand years ago as opposed to the tens of millions that mark the end of the reign of the dinosaurs—and the fact that it roamed the far north, including the Arctic, means that its DNA has been preserved in [multiple remains embedded in permafrost](https://www.snexplores.org/article/woolly-mammoth-dna-glass). For its de-extinction project, Colossal collected the genomes of nearly 60 of those recovered mammoths. Recreating the species from that raw biological material is relatively straightforward in principle, if exceedingly painstaking in practice. The work involves pinpointing the genes responsible for the traits that separate the mammoth from the Asian elephant—its close evolutionary relation—editing an elephant stem cell to express those traits, and introducing the stem cell into an elephant embryo. In the alternative, scientists could edit a newly conceived Asian elephant zygote directly. Either way, the next step would be to implant the resulting embryo into the womb of a modern-day female elephant. After 22 months—the typical elephant gestation period—an ice age mammoth should, at least theoretically, be born into the computer-age world. But speedbumps abound. The business of rewriting the genome takes extensive experimentation with hundreds of embryos to ensure that the key genes are properly edited. The only way to test if they indeed are is to follow the embryos through gestation and see if a viable mammoth pops out; the nearly two years it would take for even a single experimental animal to be born, however, would make that process impractical. What’s more, Asian elephants are highly social, highly intelligent, and [endangered](https://www.fws.gov/species/asian-elephant-elephas-maximus), raising intractable ethical obstacles to experimenting on them. Enter the mouse, an animal whose [genome lends itself](https://pmc.ncbi.nlm.nih.gov/articles/PMC9942237/) to easy manipulation with [CRISPR](https://bitesizebio.com/47927/history-crispr/#:~:text=CRISPRs%20were%20first%20identified%20in,gene%2Dediting%20tool%20was%20published.)—a gene-editing tool [developed in 2012](https://bitesizebio.com/47927/history-crispr/#:~:text=CRISPRs%20were%20first%20identified%20in,gene%2Dediting%20tool%20was%20published.), based on a natural process [bacteria use](https://pmc.ncbi.nlm.nih.gov/articles/PMC9942237/) to defend themselves in the wild. What’s more, mice need only 20 days to gestate, making for a quick turnaround from embryo to mouse pup. In the current experiment, researchers identified seven genes that code for the mammoth’s shaggy coat—identifying distinct ones that make it coarse, curly, and long. They also pinpointed one gene that guides the production of melanin—which gives the coat its distinctive gold color—and another that governs the animal’s prodigious lipid metabolism. Relying on CRISPR, they then took both the stem cell and zygote approach to rewriting the mouse’s stem cell to express those traits. The next steps involved more than a little hit and miss. Over the course of five rounds of experiments, the Colossal scientists produced nearly 250 embryos. Fewer than half of them developed to larger, more-viable 200- to 300-cell embryos, which were then implanted in the womb of around a dozen surrogate females. Of these, 38 mouse pups were born. All of them successfully expressed the gold, woolly hair of the mammoth as well as its accelerated lipid metabolism. The Colossal scientists see the creature they’ve produced as a critical development. "The woolly mouse project doesn't bring us any closer to a mammoth, but it does validate the work we are doing on the path to a mammoth,” Lamm tells TIME. “\[It\] proves our end-to-end pipeline for de-extinction. We started this project in September and we had our first mice in October so that shows this works—and it works efficiently.” There’s plenty still to accomplish. A mammoth is much more than its fur and its fat, and before one can lumber into the twenty-first century, the scientists will have to engineer dozens of other genes, including those that regulate its vasculature, its cold-resistant metabolism, and the precise distribution of its fat layers around its body. They would then have to test that work in more mouse models, and only if they succeed there try the same technique on an elephant. "The list of genes will continue to evolve,” says Lamm. “We initially had about 65 gene targets and expanded up to 85\. That number could go up or down with further analysis, but that's the general ballpark for the number of genes we think we will edit for our initial mammoths.”  Woolly mice at Colossal Biosciences lab. Courtesy of Colossal Biosciences Colossal scientists see all of this work as just a first step in developing a more widely applicable de-extinction technology. In addition to the mammoth, they would also like to bring back the [dodo](https://www.britannica.com/animal/dodo-extinct-bird) and the [thylacine](https://australian.museum/learn/australia-over-time/extinct-animals/the-thylacine/)—or Tasmanian tiger. “Our three flagship species for de-extinction—mammoth, thylacine, and dodo—capture much of the diversity of the animal tree of life,” says Beth Shapiro, Colossal’s chief science officer. “Success with each requires solving a different suite of technical, ethical, and ecological challenges.” The work can’t start soon enough. The company [points ](https://colossal.com/is-colossal-biosciences-a-real-company/#:~:text=Colossal%20Biosciences%20is%20a%20biotechnology,winning%20serial%20entrepreneur%20Ben%20Lamm.)to [studies](https://www.greenbuildermedia.com/blog/climate-change-to-kill-half-of-all-species-by-2050#:~:text=An%20estimated%20one%20million%20species,back%20against%20waves%20of%20extinction.) suggesting that by 2050 up to 50% of the Earth’s species could have been wiped out, most of them lost to the planet’s rapidly changing climate. The [Center for Biological Diversity](https://colossal.com/is-colossal-biosciences-a-real-company/#:~:text=Colossal%20Biosciences%20is%20a%20biotechnology,winning%20serial%20entrepreneur%20Ben%20Lamm.) puts the figure at a somewhat less alarming 35%, but in either case, the widespread dying could lead to land degradation, loss of diversity, the rise of invasive species, and food insecurity for humanity. Arresting climate change and the loss of species that will result is a critical step away from that brink, but one that policymakers and the public are embracing only slowly. Restoring the species that will vanish—or fortifying the genetic heartiness of those that are endangered to help them adapt to a changing world—is one more insurance policy against environmental decline. “We do not argue that gene editing should be used instead of traditional approaches to conservation, but that this is a ‘both and’ situation,” says Shapiro. “We should be increasing the tools at our disposal to help species survive.” ## Transcript We were trying to develop this complex trait of being able to survive in cold climates. So we focused mostly on woolly hair and also a gene that's associated with fat, fat metabolism. And we looked then in the mouse literature. So in mice there's just a really common what they call it model organism to test things about genetics and development and things like that. So there's a lot of information out there about mice. So we could look at the genes that look like they have an important change in mammoths, and see if the mouse version of those genes has ever been associated with a mouse that has the phenotype that we're interested in. We found ten genes that overlap there, where there have been a mouse that has a somewhere, a mouse has been born that has a variant in that same gene that gives that mouse a woolly coat phenotype. And so these all the changes that we made have been observed individually in living healthy mice before what we did that was different was put them all together in a single mouse. Asian elephants are closer genetically to mammoths than Asian elephants are to African elephants, which that sometimes blows people's minds. But so what we are working on is to use a lot of ancient DNA computational analysis, advanced editing tools, and advanced embryology to bring back those lost genes, engineer them into their closest living relatives so that we get functional de-extinction, right? It's not possible to clone an extinct species. It is possible to do functional de-extinction, where we're bringing back those core phenotypes or physical traits, and then looking at those traits that we can then rewild back into their natural habitat. They say that they're going to resurrect de-extinct. Putting mouse mutations back in a mouse isn't resurrecting anything. And even if you could do that to an Asian elephant and make an Asian elephant that had the pretty color hair and sort of luxurious hair, um, that's not resurrecting anything. That's taking the taking mouse mutations and putting it into an elephant. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/7264043/colossal-biosciences-woolly-mouse-bring-back-mammoth/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/7264043/colossal-biosciences-woolly-mouse-bring-back-mammoth/"},"headline":"Scientists Have Bred Woolly Mice on Their Journey to Bring Back the Mammoth","datePublished":"2025-03-04T13:00:13.000Z","dateModified":"2026-08-04T07:44:23.383Z","description":"The mice were bred using woolly mammoth DNA.","url":"https://time.com/7264043/colossal-biosciences-woolly-mouse-bring-back-mammoth/","keywords":["climate change","Tech"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltc387c2794e5fe2bd/6998c4901f670948fbf56239/241214-Colossal-Mice-Finals-19.png?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Jeffrey Kluger","jobTitle":"Editor at Large","url":"https://time.com/author/jeffrey-kluger/"}],"articleSection":"Science","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltc387c2794e5fe2bd/6998c4901f670948fbf56239/241214-Colossal-Mice-Finals-19.png?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"241214-Colossal-Mice-Finals-19","caption":"Colossal Biosciences Woolly Mouse and normal mouse","creditText":"Courtesy of Colossal Biosciences","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/science/","name":"Science"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/climate-change/","name":"climate change"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/7264043/colossal-biosciences-woolly-mouse-bring-back-mammoth/","name":"Scientists Have Bred Woolly Mice on Their Journey to Bring Back the Mammoth"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"Scientists Genetically Engineer Mice with Woolly Mammoth Like Hair","description":"Extinction is typically for good. Once a species winks out, it survives only in memory and the fossil record. When it comes to the woolly mammoth, however, that rule has now been bent. It’s been 4,000 years since the eight-ton, 12-foot, elephant-like beast walked the Earth, but part of its DNA now operates inside several litters of four-inch, half-ounce mice created by scientists at the Dallas-based Colossal Laboratories and Biosciences.","thumbnailUrl":"https://cdn.jwplayer.com/v2/media/gnBw4dT1/poster.jpg?width=720","uploadDate":"2025-03-04T19:21:46.000Z","contentUrl":"https://cdn.jwplayer.com/manifests/gnBw4dT1.m3u8","embedUrl":"https://time.com/7264043/colossal-biosciences-woolly-mouse-bring-back-mammoth/","duration":"PT2M24S","potentialAction":{"@type":"SeekToAction","target":"https://time.com/7264043/colossal-biosciences-woolly-mouse-bring-back-mammoth/?jw_start={seek_to_second_number}","startOffset-input":"required name=seek_to_second_number"}}] ```