New research indicates a correlation between the lifespan of mammals, such as cats, and the size of their brains and the complexity of their immune systems. An international team of scientists, spearheaded by the University of Bath, examined evolutionary differences across mammal species and discovered that species with larger brains and longer lifespans tend to allocate more resources to immune-related genes. The research underscores that significant genomic changes, rather than individual genes, are instrumental in shaping longevity.

The scientists analyzed the maximum lifespan potential (MLSP) of forty-six mammal species and mapped the genes shared among them. The MLSP reflects the longest recorded lifespan of a species, as opposed to the average lifespan, which is influenced by factors like predation and resource availability. Published in the journal Scientific Reports, the study revealed that longer-lived species possess a greater number of genes from gene families associated with the immune system, suggesting this is a primary mechanism driving the evolution of extended lifespans in mammals. For example, dolphins and whales, known for their large brains, have maximum lifespans of 39 and up to 100 years, respectively, while smaller-brained creatures like mice may only live one or two years.

However, some species, such as mole rats, defy this trend, living up to twenty years despite their smaller brains. Bats also exhibit longer lifespans than expected relative to their brain size. Upon genomic analysis, both these species displayed a higher concentration of immune system-related genes. These findings suggest that the immune system plays a crucial role in sustaining longer lives, possibly through mechanisms like eliminating old and damaged cells, controlling infections, and preventing tumor formation. The study highlights that broad genomic changes, such as the duplication and expansion of entire gene families, are vital in shaping lifespan, rather than small mutations in single genes or pathways.

Dr. Benjamin Padilla-Morales, from the Milner Centre for Evolution and the University of Bath's Department of Life Sciences, the study's first author, stated, "It has been known for a while that relative brain size is correlated to longevity; the two traits have a shared evolutionary direction, and having a larger brain potentially gives behavioral benefits. But our study also highlights the surprising role of the immune system not just in combating disease but in helping longer lives across mammalian evolution."

He continued, "Larger-brained species do not simply live longer due to ecological reasons; their genomes also show parallel expansions in genes related to survival and maintenance. This suggests that brain size and immune resilience seem to have walked hand-in-hand in the evolutionary adventure towards longer lives." The researchers plan to further investigate cancer-associated genes highlighted in the study to better understand the connection between these genes and lifespan and why there is such variation in lifespans among mammals.