Ancient Denisovan DNA Still Tunes the Immune Systems of Pacific Islanders, Yale-Led Study Finds

Tens of thousands of years after a now-extinct human cousin vanished, its DNA is still at work in the bodies of people living across the Pacific. A major new study led by Yale University finds that genetic material inherited from Denisovans continues to fine-tune the immune systems of present-day Oceanian populations, helping them fend off viruses and bacteria.

The research, published in the journal Science, offers one of the most comprehensive looks yet at human genetic diversity in Oceania — a region long underrepresented in genomics. By sequencing genomes from Near Oceania, including Papua New Guinea, the team found that the ancestors of these populations interbred with at least three genetically distinct groups of Denisovans, far more structure than previously appreciated. Denisovans, a sister lineage to Neanderthals, were unknown to science until 2010, when DNA from a fingerbone in Siberia's Denisova Cave revealed an entirely new branch of the human family — and people in Oceania carry more Denisovan ancestry than any other population on Earth.

Those ancient encounters left a lasting mark. The scientists identified thousands of archaic gene variants that turn genes up or down, and found them strikingly concentrated in immune and antiviral pathways. A substantial share affected interferon-gamma signaling, a cornerstone of the body's defense against infectious pathogens. In effect, Denisovan DNA appears to have handed these populations a head start against the specific microbes their ancestors faced in the islands of Near Oceania.

That inheritance may be a double-edged sword. The same variants that bolster antiviral defenses could also influence the risk of autoimmune disease, in which an overactive immune system attacks the body's own tissues. The researchers also found evidence that Denisovan DNA shaped skeletal development, hinting that the archaic legacy reaches beyond immunity into the very architecture of the body.

Beyond the specific findings, the study addresses a longstanding blind spot in genetic research, which has overwhelmingly focused on people of European ancestry. By centering populations of Oceania, the authors argue, scientists can uncover adaptations — and disease risks — that would otherwise remain invisible, while filling in a richer picture of how our species mingled with its archaic relatives on the far edges of the ancient world.

The work also carries practical stakes for medicine. Because genetic databases skew heavily toward people of European descent, variants common in Pacific populations can be missed by the algorithms that increasingly guide diagnosis and drug prescribing. Understanding how Denisovan-derived variants shape immune responses, the researchers say, could improve everything from vaccine design to the treatment of autoimmune conditions in communities that medical science has too often overlooked.