Some bats live astonishingly long for their size. A tiny Brandt’s myotis — a bat that weighs less than a tablespoon of water — was once recaptured 50 years after it was first banded, a feat of longevity that, scaled to body size, dwarfs our own. Bats also rarely develop cancer. A new genomic study published in Nature suggests how they pull off both, and the answer centers on an unusually aggressive immune system.
The puzzle: Peto’s paradox
Biologists have long been intrigued by a riddle known as Peto’s paradox: if every cell division carries a small risk of a cancer-causing mutation, then big, long-lived animals — with vastly more cells dividing over vastly more years — ought to be riddled with cancer. Yet they are not. Whales, elephants and long-lived bats all defy the naive math, which means evolution has repeatedly invented anti-cancer defenses. Understanding those natural solutions is a central goal of the young field of geroscience, which studies the biology of aging itself.
What the researchers did
A team led by Juan Manuel Vazquez (then at UC Berkeley, now Penn State), with collaborators including Peter Sudmant and Elise Lauterbur, analyzed eight genomes from the Myotis genus — a group of small, insect-eating bats that includes some of the longest-lived mammals relative to body size. By comparing species with different lifespans, they could look for genetic features that track with living longer.
What they found
Two themes stood out. First, longer-lived species carried higher levels of cancer-fighting genes, and there was substantial overlap between aging-related genes and immune-defense genes — hinting that, in bats, staying young and fighting disease are deeply intertwined.
Second, and most striking, damaged cells in long-lived bats appear to prioritize self-destruction over DNA repair — the opposite of the typical mammalian response. Most mammals try hard to fix damaged DNA, which occasionally allows a flawed cell to survive and turn cancerous. The long-lived bats seem to follow a “better safe than sorry” rule: a cell that looks dangerous is simply eliminated. Over a lifetime, that bias could sharply reduce the odds that any single cell becomes a tumor.
The Myotis genomes also carried an unusually large arsenal of genes for interacting with DNA viruses. Bats are famous reservoirs of viruses they tolerate without getting sick — a trait with obvious relevance to pandemic biology — and the study suggests their immune systems run on constant high alert, managing persistent infections while somehow avoiding the chronic inflammation that ages other animals.
How this fits the broader search
Bats join a small cast of “longevity mutants” that researchers mine for anti-aging and anti-cancer tricks. The naked mole rat, for instance, resists cancer through unusually gummy molecules that keep cells from crowding together; some whales carry extra copies of tumor-suppressor genes. Each species offers a different natural experiment. What makes the bat findings notable is the immune angle: rather than a single tumor-suppressor trick, bats seem to couple longevity to a whole immune strategy.
Why it matters — and the caveats
“Maybe you can improve your immune system so it doesn’t decline in old age… ways to fight off tumors so our immune system doesn’t get tired,” Vazquez said. That points at one of aging’s central problems — immunosenescence, the gradual weakening of immune defenses that leaves older people more vulnerable to infection and cancer alike. If the genetic features that keep bat immunity vigorous could be understood and, someday, mimicked, it might inform new approaches to cancer immunotherapy or healthy aging.
The important caveat: this is basic comparative genomics, not a therapy. Findings in bats are a long way from human treatments, and evolution’s solutions do not always transfer across species. But by revealing how one lineage married a long life to cancer resistance, the work sketches new hypotheses worth testing. Preliminary research; not medical advice.