The Ministry of Oceans and Fisheries National Institute of Fisheries Science announced that it has decodified the complete genome of the extinct Dokdo sea lion (Neophoca), known to have become extinct since the 1970s, and published the related research results in the online edition of the international academic journal 'BMC Biology' on the 1st.
The Dokdo sea lion is a marine mammal that inhabited the Korean Peninsula but became extinct in the 1950s to 1970s due to overexploitation during the Japanese colonial period. The most similar species are the California sea lion and the Galapagos sea lion. According to the International Union for Conservation of Nature (IUCN), about 50,000 were living in Northeast Asian waters until the mid-1800s, but this sharply declined to about 50 in the 1950s, and extinction was officially declared in the 1990s.
Researchers from the National Institute of Fisheries Science, Seoul Grand Park, the Genome Research Foundation, Ulsan National Institute of Science and Technology (UNIST), Aging Lab, and the Russian European Genome Institute extracted deoxyribonucleic acid (DNA) from 16 bone fragments of the Dokdo sea lion excavated in the Dokdo and Ulleungdo regions, obtaining a big data set totaling 8.4 terabytes. They also succeeded in analyzing the complete genome of the Dokdo sea lion.
The analysis results have proven for the first time in the world that the Dokdo sea lion evolved into a completely distinct species, separating from the California sea lion about 2 million years ago. Traces of gene exchange with other species such as seals and giant sea lions were also confirmed.
In particular, the Dokdo sea lion maintained genetic diversity even just before extinction. The researchers explained, 'This result shows that the cause of extinction was not genetic factors but indiscriminate overexploitation by humans.'
Choi Yong-seok, head of the National Institute of Fisheries Science, noted, 'This international collaborative research not only revealed the origin of the Dokdo sea lion but also strengthened the geographical and historical uniqueness of our native species by being mentioned in an international journal. We will continue to study the genetic characteristics of various indigenous species in our waters to enhance biological sovereignty and contribute to establishing a foundation for future industries.'
References
BMC Biology (2025), DOI: https://doi.org/10.1186/s12915-025-02351-3