Scientists discover what drives the maximum lifespan potential of mammals

Scientists have long wondered why some mammals live dramatically longer than others. While humans can reach ages beyond a century, certain whales surpass two centuries, and elephants easily live decades, some small mammals, like mice or shrews, barely survive a couple of years. The secret to these striking differences may lie hidden within the genes of mammals, and a new study sheds intriguing light on this evolutionary puzzle.

An international team of researchers, led by Dr. Benjamin Padilla-Morales from the Milner Centre for Evolution at the University of Bath, has revealed that the maximum lifespan potential (MLSP)—the longest lifespan recorded within a species—is closely tied to expansions in gene families related to the immune system and brain size.

"It’s been known for a while that relative brain size is correlated to longevity," explains Dr. Padilla-Morales. "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."

Researchers examined genomes from 46 mammal species, including whales, bats, dolphins, and mole rats. Unlike average lifespan, which depends heavily on external factors like predators or food availability, MLSP reflects a species’ natural biological limits. Surprisingly, species with extended lifespans consistently showed significant expansions in gene families tied to immune functions.

Why would immune genes influence lifespan? Researchers suggest the immune system helps organisms manage aging by removing damaged cells, controlling infections, and preventing tumors. These genetic expansions don't simply boost resistance to diseases; they seem critical in protecting mammals against age-related decline.

Bats offer a remarkable example. Despite their small brains, bats live unusually long, healthy lives for their size—often 20 years or more. Upon examining bat genomes, researchers discovered notable expansions in immune-related genes. This genetic boost might help bats avoid common age-linked conditions, such as cancer and viral infections, which typically limit longevity.

Similar immune gene expansions appear in mole rats, small mammals known for defying normal lifespan expectations. Mole rats can survive for decades, an impressive feat for rodents. This pattern points strongly toward immune system resilience as a cornerstone in the evolution of mammalian longevity.

Yet, the relationship between lifespan and genetics is not solely about immunity. The researchers also confirmed that brain size relative to body mass significantly correlates with longer lifespans. Larger-brained mammals, such as whales and dolphins, often live dramatically longer. Dolphins, for instance, can reach nearly 40 years, and certain whale species exceed a century, reflecting this robust link between brain size and longevity.

However, this isn't universally true. Some animals with smaller brains can still achieve long lives, thanks to immune genetic factors. This suggests brain size and immune strength evolved together, creating complementary strategies to enhance longevity.

Dr. Padilla-Morales notes, "Bigger-brained species don’t just live longer because of ecological reasons. Their genomes show parallel expansions in genes linked to survival and maintenance. Brain size and immune resilience seem to have walked hand-in-hand in the evolutionary journey toward longer lives."

Previous studies identified single genes affecting lifespan, such as TP53 in elephants, which suppresses tumors, or DNA repair genes in whales. However, this research emphasizes broader genomic trends rather than individual genes. Instead of small genetic tweaks, large-scale changes in gene family sizes appear crucial in longevity evolution.

Genes responsible for repairing DNA, regulating cell cycles, and managing oxidative stress frequently expand in long-lived mammals. These expansions increase organisms' ability to sustain cellular integrity, reducing susceptibility to aging-related diseases.

The scientists also noted how gene duplication events, where genes replicate within the genome, significantly drive these expansions. While some duplicated genes become inactive, others gain new roles, enhancing an organism’s biological complexity and adaptability—key factors in extending lifespan.

Despite significant progress, unanswered questions remain. The researchers plan to further investigate cancer-related genes found in their study. Understanding how these genes influence longevity may clarify why lifespans vary dramatically across mammals. Such insights could eventually lead to breakthroughs in human medicine, particularly for diseases associated with aging.

The team's comprehensive genome-wide analysis is a significant step forward. It integrates previous studies and expands upon them by accounting for factors like body size, brain size, and population dynamics, all known to influence lifespan. This holistic approach provides a clearer, more accurate picture of longevity's genetic basis.

This research underscores the power of comparative genomics, highlighting how gene family expansions shape mammalian lifespans. The findings not only help scientists understand evolutionary history but could guide future health interventions, potentially transforming how aging-related diseases are prevented and treated.

For humans, this discovery raises intriguing possibilities. Could enhancing certain immune-related genes lead to longer, healthier lives? Could understanding genetic longevity patterns improve treatments for aging diseases like Alzheimer's or cancer? While these questions remain speculative, the research clearly positions immune resilience and brain complexity at the heart of longevity evolution.

Dr. Padilla-Morales summarizes the implications succinctly: "Our findings suggest the immune system is central to sustaining longer life. Broad genomic changes—such as the duplication and expansion of entire gene families—are crucial in shaping lifespan."

Understanding these evolutionary mechanisms offers exciting avenues for future research and, potentially, human longevity. With ongoing research, science might unlock new ways to extend life, enhancing health and quality well into advanced age.

Research findings are available online in the journal Scientific Reports.

Note: The article above provided above by The Brighter Side of News.

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