Bigger Brains Lead to Longer Lifespans, Says New Study

Big brains may do more than boost intelligence—they could also be tied to stronger immune systems and longer lifespans, according to a new genetic study from the University of Bath.

Published in Scientific Reports, the study analyzed genomic data from 46 mammal species, including cats, pandas, and dolphins, and found that longer lifespans are linked to expansions in immune-related gene families and larger relative brain sizes, especially in species like humans, elephants, and primates.

“We identified 236 gene families showing significant positive correlations with maximum lifespan potential across the mammalian phylogeny,” the researchers wrote. “Genes in these families are enriched in immune system functional annotations and among genes previously associated with ageing and longevity.”

Maximum lifespan potential refers to the age reached by the longest-lived individual in a species, which can vary drastically. Unlike average lifespan, which is influenced by environmental factors like war, predators, or disease, MLSP reflects the species’ biological limit.

According to data by the World Health Organization, in 2021, the average human life expectancy was 71.3 years. The current oldest living human is Ethel Caterham, born in 1909, from the United Kingdom. She is 115 years old. However, the oldest person ever recorded was Jeanne Calment of France, who lived to be 122.

In contrast, the average life expectancy of a dog generally ranges from 10 to 13 years. Spike, the verified oldest living dog, is a 25-year-old Chihuahua mix from the United States. However, the oldest verified dog on record was an Australian cattle dog named Bluey, who lived to be 29. Conversions between a dog’s actual age and estimated “human age” can vary based on size and breed.

Research into the relationship between brain size and longevity dates back decades. Building on this earlier research, scientists believe that uncovering the genetic basis of MLSP could reveal how evolution shapes aging by influencing cellular decline and energy metabolism.

According to the researchers, the study accounted for physical traits like body and brain size, and life history factors such as age at maturity and gestation time, when analyzing the genetic patterns linked to how lifespan evolves.

“We uncovered evidence of a shared molecular machinery associated with the evolution of maximum lifespan potential and relative brain size, with 161 gene families significantly related to both phenotypes when included in the same models,” they said. “This common genomic signature aligns with the established evolutionary relationship between lifespan and relative brain size in vertebrates. Conversely, no associations were found with gestation time, age at sexual maturity, or body mass.”

Beyond just the number of genes, the researchers found that the genes linked to MLSP were more active in humans and could be used in more varied ways to produce different proteins. This suggests that both the level of gene activity and the flexibility in how genes are used might help support longer lifespans.

Additionally, many of these genes were already known to be connected to human longevity, pointing to possible shared biological patterns between what influences species-wide lifespan and what affects individual longevity.

The study’s findings suggest that both immune system function and brain size play a central role in the evolution of long lifespans, and that the same genetic mechanisms may underlie lifespan differences across species and within humans.

“These novel discoveries enhance our comprehension of the mechanisms underpinning the ageing process,” the study said. “Given the reversible nature of epigenetic data, these inquiries illuminate promising avenues for therapeutic interventions in aging and age-related ailments, including cancer.”