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What causes cats to often live longer than dogs? According to recent studies, their larger brains and more complicated immune systems may explain why they live longer.
Studying evolutionary variations among mammalian species, an international team of researchers headed by the University of Bath discovered that mammals with larger brains and longer lifespans tend to invest more in immune-related genes. Their results reveal how broad genomic modifications, as opposed to single genes, influence longevity.
The study appears in Scientific Reports.
The researchers sequenced the genes common within 46 species of mammals and examined their maximum lifespan potential. Rather than the average lifespan, which is influenced by factors including predation and the availability of food, the maximum lifespan potential (MLSP) is the longest documented longevity of a species.
The study indicated that longer-lived species have more genes belonging to the gene families linked to the immune system, implying this as a key driver of the development of longer lifespans among mammals.
For instance, dolphins and whales with fairly large brains have maximum lifespans of 39 and up to 100 years; animals with smaller brains, like mice, may only live up to two years.
Some animals, like mole rats, meanwhile, defied this pattern and lived up to 20 years despite their small brains. Bats also lived longer than one might anticipate considering their small brains, but an analysis of their genomes revealed that both species have more immune system-related genes.
The findings imply that maybe by eliminating aged and damaged cells, regulating infections and limiting tumor development, the immune system is fundamental to maintaining longer lifespan.
The study reveals that broader genomic changes—duplication and expansion of full gene families—not only minor alterations (such in single genes or pathways) are important in determining lifespan.
Researchers claimed that relative brain size is linked to longevity—the two traits have a common evolutionary history, and having a bigger brain may provide behavioral benefits.
The study, however, draws attention to the unexpected function of the immune system not just combating diseases but also in promoting longer life throughout mammalian evolution.
Larger-brained organisms don’t just live longer for ecological reasons; their genomes also reveal parallel expansions in genes connected to survival and maintenance.
This suggests that in the evolutionary path toward longer lives, brain size and immunological resilience appear to have walked together hand in hand.
The researchers next intend to look at the cancer-related genes underlined in the study to further unravel the connection between these genes and the lifespan to know why there is such a disparity in lifespans in mammals.
Sources:
Huseyin Kilili et al. (2025). Maximum lifespan and brain size in mammals are associated with gene family size expansion related to immune system functions, Scientific Reports. DOI: 10.1038/s41598-025-98786-3
Mammalian lifespan linked to brain size and immune system function. https://phys.org/news/2025-05-mammalian-lifespan-linked-brain-size.html
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