Mammal's lifespans linked to brain size and immune system function, says new study
University of Bath
An international team of scientists led by the University of
Bath studied evolutionary differences between mammal species and found that
those with bigger brains and longer lifespans tend to invest more heavily in
immune-related genes. Their findings show how broad genomic changes, rather
than individual genes, shape longevity.
The researchers looked at the maximum lifespan potential of
46 species of mammals and mapped the genes shared across these species. The
maximum lifespan potential (MLSP) is the longest ever recorded lifespan of a
species, rather than the average lifespan, which is affected by factors such as
predation and availability of food and other resources.
The researchers, publishing in the journal Scientific Reports, found that longer-lived species had a greater number of genes belonging to the gene families connected to the immune system, suggesting this as a major mechanism driving the evolution of longer lifespans across mammals.
For example, dolphins and whales, with relatively large
brains have maximum lifespans of 39 and up to 100 years respectively, those
with smaller brains like mice, may only live one or two years.
However, there were some species, such as mole rats, that
bucked this trend, living up to 20 years despite their smaller brains. Bats
also lived longer than would be expected given their small brains, but when
their genomes were analysed, both these species had more genes associated with
the immune system.
The results suggest that the immune system is central to
sustaining longer life, probably by removing aging and damaged cells,
controlling infections and preventing tumour formation.
The study shows that it's not just small mutations (like in
single genes or pathways) but larger genomic changes (duplication and expansion
of whole gene families) can be crucial in shaping lifespan.
Dr Benjamin Padilla-Morales, from the Milner Centre for
Evolution and the University of Bath's Department of Life Sciences, was first
author of the study.
He said: "It's been known for a while that relative
brain size is correlated to longevity -- the two characteristics have a shared
evolutionary path, and having a larger brain potentially offers behavioural
advantages.
"However, our study also highlights the surprising role
of the immune system not just in fighting disease, but in supporting longer
life across mammalian evolution.
"Bigger-brained species don't just live longer because
of ecological reasons; their genomes also show parallel expansions in genes
linked to survival and maintenance.
"This shows that brain size and immune resilience seem
to have walked hand-in-hand in the evolutionary journey toward longer lives.
The researchers next plan to investigate the cancer-related genes highlighted in the study, to further unpick the relationship between these genes and lifespan to understand why there is such a difference in lifespans in mammals.
