Hope from the Lab: Genome of the Northern White Rhino Decoded

The northern white rhino (Ceratotherium simum cottoni) is functionally extinct. Since the death of the last known male, Sudan, in 2018, only two females remain worldwide: Najin and Fatu, both at Ol Pejeta Conservancy in Kenya. Neither can carry a calf to term anymore. But an international research group has now achieved an important breakthrough: it has decoded the complete genome of this subspecies.

What the genome means for its rescue

In May 2025, an international research team published the first complete, high-resolution reference genome of the northern white rhino in the journal PNAS. The genetic information came from frozen skin cells of the bull Angalifu, who died in 2014 and had lived at the San Diego Zoo. Using state-of-the-art sequencing techniques, including long-read sequencing, optical mapping, and Hi-C mapping, the genetic material could be decoded almost without gaps.

This genetic map forms the basis for targeted, quality-assured conservation measures, both for the northern white rhino and for other threatened species.

1. Greater precision in stem-cell technologies

For years, researchers have been trying to obtain induced pluripotent stem cells (iPS cells) from skin cells, cells that can develop into sperm or egg cells in the lab. The new reference genome helps detect defects in these cells at an early stage, such as genetic damage or mutations. Only healthy, stable cell lines are meant to be used for reproduction.

2. Comparison and quality control

The genome serves as a benchmark: all other cell lines, iPS cells, or embryos can be compared against it. Differences become visible, defective lines can be discarded, and promising ones can be promoted selectively. This increases the chances of success for procedures such as in vitro fertilization (IVF) or stem-cell derivation.

3. Preserving genetic diversity

The study surprisingly shows that the northern white rhino has retained a degree of genetic diversity despite its drastic population decline. At the same time, comparison with the southern white rhino (Ceratotherium simum simum) revealed that the genetic differences between the subspecies are relatively small. This makes it easier to use southern females as surrogates and to build stable populations over the long term.

4. Improving health and fertility more precisely

Specific sections of the genome were identified that are associated with fertility, immune defense, or cell division. These markers will help in the future to select embryos with good survival and reproductive prospects, a major advantage in a project where every embryo counts.

5. A model for other threatened species

The publication is important not only for the northern white rhino. Such methods could also become relevant in the future for other highly threatened species, such as the Sumatran rhino (Dicerorhinus sumatrensis) or the extremely rare northern hairy-nosed wombat (Lasiorhinus krefftii), whose population is limited to a few dozen animals. The genome project thus becomes a model case of modern conservation biotechnology.

Biotechnology as the last rescue?

The rescue of the northern white rhino is considered one of the most ambitious projects in technology-based conservation. Given that no reproductively capable animals remain, scientists are placing all their hopes in biotechnological methods, above all in vitro fertilization (IVF) and stem-cell technologies.

Embryos from the lab

More than 30 embryos have already been created from Fatu’s egg cells and frozen sperm from deceased bulls. These are stored frozen in specialized facilities and are waiting to be transferred into suitable surrogates. Females of the closely related southern white rhino subspecies serve as surrogate mothers. Initial implantation attempts have been promising, but no pregnancy has yet been carried to term.

Germ cells from stem cells

Researchers in Japan and Europe are working on producing iPS cells from skin cells, from which egg cells and sperm can in turn be grown. The goal is to make usable again the genetic legacy of animals from which no fertilizable cells remain. The combination of IVF and stem-cell technology could therefore not only save the northern white rhino, but also become a model for other highly threatened animal species.

Timeline: The rescue attempt for the northern white rhino

• 2009: Four of the last eight living animals are moved from Dvur Kralove Zoo to Ol Pejeta Conservancy (Kenya), including Sudan, the last reproductively capable bull.
• 2014: The last breeding bull (Angalifu) outside Africa dies at the San Diego Zoo Safari Park. Cells from his skin are frozen, a decisive step for later genome research.
• 2018: The last male northern white rhino (Sudan) dies at Ol Pejeta Conservancy. Since then, the subspecies has been considered “functionally extinct.” The international BioRescue research project begins developing alternative reproductive technologies.
• 2019–2022: Fatu’s last fertile egg cells are removed regularly under general anesthesia. The eggs are fertilized with sperm from deceased bulls. The first embryos are created.
• December 2022: More than 30 embryos have been created and are waiting frozen for later implantation.
• January 2023: First embryo transfer into a southern surrogate. The implantation is technically successful, but ends in miscarriage due to an infection.
• February 2025: There are now 36 viable embryos ready for transfer.
• May 2025: Publication of the complete genome in PNAS.
• April 2026: A total of 39 viable embryos have now been created, and the role of southern white rhinos as surrogates has been further optimized; embryo-transfer success rates are rising.

Challenges and ethical questions

Despite all the technological advances in reproductive medicine and stem-cell research, restoring an extinct animal taxon remains associated with major challenges:

• Reproduction: The two last females, Najin and her daughter Fatu, are no longer able to carry young themselves. That removes the possibility of natural reproduction. All further measures therefore have to rely on artificial fertilization and the use of surrogates.
• Technology: The promising method of producing so-called iPS cells from skin cells and developing functional egg cells and sperm from them is technically demanding. Previous attempts have involved high error rates. Such errors can impair the viability of the embryos.
• Ethics: Should humans “bring back” a taxon that was wiped out through human failure? Will these animals become merely symbols of technical feasibility, or can they be given a life appropriate to the species? And are the effort and resources proportionate to the chances of success, especially given the large number of threatened species that still have a real chance of survival today?
• Habitat: Even if it became possible to rebuild a small population of northern white rhinos, where would the animals go? Their original habitats in Central Africa have been severely affected by political instability, poaching, and land loss. A safe, extensive, and permanently protected habitat is, however, a prerequisite for any successful reintroduction. Without that foundation, the survival of a recreated taxon would remain uncertain in the future as well.

These questions show that scientific progress alone is not enough. The return of an extinct animal confronts us with complex trade-offs among technology, ethics, and ecology.

Hope meets reality

Sequencing the genome is a scientific breakthrough. It shows how far biotechnology in conservation has come, but also how large the remaining gaps are. Technology alone will not save the northern white rhino. That will also require political determination, public debate, and a firm willingness to learn from the mistakes of the past.

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Sources

• Ionescu, A. (2026, April 26). Northern white rhino inches back from extinction with 39 lab-grown embryos. Earth.com. https://www.earth.com/news/northern-white-rhino-inches-back-from-extinction-with-39-lab-grown-embryos/
• Phys.org. (2025, May 15). Genome of near‑extinct northern white rhino offers hope for reviving endangered species. Phys.org. Retrieved May 21, 2025, from https://www.phys.org/news/2025-05-genome-extinct-northern-white-rhino.html
• Wang, G., Korody, M. L., Brändl, B., Hernandez-Toro, C. J., Rohrandt, C., & Hong, K. et al. (2025). Genomic map of the functionally extinct northern white rhinoceros (Ceratotherium simum cottoni). Proceedings of the National Academy of Sciences, 122(20), Article 2401207122. https://doi.org/10.1073/pnas.2401207122