Recent studies suggest that our evolutionary predecessors may have prioritized gender over survival, potentially explaining why men tend to have shorter lifespans than women.
Historically and globally, men usually live shorter lives than women. To understand the reasons behind this evolutionary trend, researchers at the Max Planck Institute in Germany focused on insights from our animal relatives rather than solely examining human history.
Their study, published in Advances in Science, analyzed over 1,000 animal species to identify evolutionary traits associated with gender differences in lifespan.
The team discovered that while genetics plays a role, monogamy is also significant in influencing male lifespan. In contrast, parenting may contribute to women’s longer lives.
In humans, women live on average 5 years longer than men, but this trend is not unique to our species. In fact, 72% of mammals show that females live on average 12% longer than their male counterparts, with some female moose living more than twice as long as males.
However, this pattern doesn’t hold true across all animal species. In birds, males frequently outlive females.
A primary explanation lies in chromosomes, which are fundamental to gender differences. Female mammals possess two X chromosomes, whereas males have a shorter Y chromosome.
According to Dr. Johanna Staerk, the lead researcher, “Men’s single X chromosome means they are particularly susceptible to harmful mutations, as they lack a second copy for compensation,” she explained to BBC Science Focus.
“The ‘toxic Y’ hypothesis posits that the Y chromosome may harbor genetic factors that negatively influence health and aging.”
Conversely, in birds with ZW chromosomes, males have two Z chromosomes while females possess one Z and a truncated W chromosome. However, if chromosomes were the sole factor, males would live longer in all bird species.
“Some species demonstrate the opposite of what we expect,” Staerk noted. “In many birds of prey, for instance, females exhibit longer lifespans than males. This indicates that sex chromosomes alone cannot explain the patterns.”
What other factors are at play? Researchers believe that the issue involves more than mere genetic sex; it includes reproductive strategies. While birds typically show monogamous behavior, only a minority of mammals do.
“Males frequently bear the burden of mating endeavors,” Staerk said. “To attract mates, they develop traits like big horns and manes that require energy investments, increasing their risk of injury and reducing their lifespan.”
Attractive and robust males tend to father more offspring, but the biological resources required for developing larger muscle and horn structures negatively impact their lifespans. In monogamous species, the competition is less intense, allowing males to avoid such trade-offs during evolution, resulting in smaller lifespan gaps between sexes.
One intriguing finding highlighted how parenting influences lifespan. While one might assume that parental responsibilities detract from longevity due to energy exertion, the opposite was observed: caregiving genders often live longer, especially in species like primates, where offspring require extended care.
For example, a mother chimpanzee may care for her young for up to a decade. This implies that mothers who live longer are better positioned to nurture their offspring.
“Extended lifespans enable caregivers to obtain selective advantages by ensuring that their young reach maturity,” stated Staerk.
However, it remains challenging to determine definitively whether the longevity benefits stem from parenting alone or from monogamy.
Ultimately, being a dedicated partner and parent seems crucial to achieving a longer lifespan for men, particularly from an evolutionary standpoint.
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Source: www.sciencefocus.com
