Why Female Longevity Outlives Males Across Species: Patterns in Mammals, Birds, and Humans

Rob Salguero-Gomez of the University of Oxford synthesizes a broad pattern in biology: females often outlive males across many species, but the magnitude and direction of the gap vary by taxa and environment. In mammals, females typically enjoy a longer life than males, especially in the wild where the advantage averages around 19 percent, driven by genetic factors, testosterone effects, and reproductive trade-offs. In birds, the pattern can flip, with males sometimes living longer in captivity but females often prevailing in the wild due to energy costs of egg production and parental care. The article also notes exceptions in insects, reptiles, and fish where social structure and colony life can dramatically alter sex-based survival. In humans, women generally live longer than men worldwide, yet healthspan and quality of life complicate the picture. Overall, longevity differences arise from a mix of chromosomes, hormones, mating systems, and ecological risks, not a universal law. — The Conversation, Rob Salguero-Gomez

Overview

The article by Rob Salguero-Gomez, drawing onJohanna Staerk’s Science Advances study, surveys sex differences in longevity across the Tree of Life, highlighting that female longevity is common but not universal. In mammals, data from hundreds of species show a female advantage in life expectancy, especially in the wild where the gap averages about 19 percent. In contrast, birds exhibit a more mixed pattern where males often outlive females in zoos, yet in the wild the advantage frequently shifts toward females, with several species showing female longevity costs tied to egg production and parental care. The piece also emphasizes that humans fit within this broader pattern, where women tend to outlive men by roughly five years globally, though better maternal care and health improvements have nuanced this edge across cultures and history.

Two major explanations frame the differences: genetic/hemisome factors and life-history trade-offs driven by sexual selection. The heterogametic hypothesis (XY in mammals, ZW in birds) predicts shorter lifespans for the sex with two different sex chromosomes, but it cannot fully explain all exceptions, such as long-lived female raptors. The second explanation—life-history and sexual selection trade-offs—posits that traits enhancing reproductive success (large size, weaponry, aggressive mating strategies) reduce survival, especially in polygynous mammals and birds. The article argues that non-monogamous mammals with larger male competition exhibit the largest female advantage, illustrating how mating systems shape survival outcomes.

Mammals: Female Advantage and Its Limits

Within mammals, wild populations show a pronounced female advantage due to risks associated with male competition, territory defense, and mate-seeking behavior. The Compadre database and field studies in elephants and moose illustrate how males incur higher mortality from combat and risky solitary ranging. Genetics also contribute: recessive X-linked mutations and higher testosterone can influence immune function and overall health, helping explain why females often outlive males in many mammal species.

"Longevity differences reflect life-history trade-offs and mating-system dynamics" - Johanna Staerk, evolution researcher

Birds: The Male Advantage and Its Reversal

In birds, the pattern diverges. Among 648 studied species in zoos, males outlived females in about 68 percent of cases, with an average male longevity advantage of around 5 percent. In the wild, however, the advantage often reverses, with females living longer in many species. Female birds bear heavy reproductive costs, including egg production, incubation, and chick-rearing, which can shorten female lifespans. The heterogametic nature of birds (ZW females) may expose females to greater genetic risks, though some exceptions challenge simple rules. Notably, raptors such as buzzards and eagles can show female longevity advantages, while in some cases captivity reverses the trend, a puzzle still under study.

"Female birds pay heavy reproductive costs, which can translate into shorter lifespans" - Staerk

Beyond Fur and Feathers: Other Taxa

Insects reveal dramatic contrasts: some female moths or mayflies die soon after reproducing, while males persist longer, but social insects like ants or bees can see long-lived queens outliving workers by years or decades, illustrating how social organization can reshape sex-specific survival. Amphibians and reptiles show mixed patterns, with male mating calls and combat shortening lifespans in some frogs, while females may incur costs through reproduction. In stickleback fish, males often die after breeding as parental care is energetically costly, while females reproduce again later, balancing lifespans with fecundity.

Humans in Context

Across cultures and history, women tend to live longer than men, with modern populations exposing a strong female edge in life expectancy. In Japan, female life expectancy exceeds 87 years versus 81 for men; Hadza hunter-gatherers show the same general pattern. Yet the advantage is not purely about quantity of years; women often experience years lived in poorer health, including osteoporosis and dementia, suggesting longevity comes with health-quality trade-offs. The author notes that the human female edge is likely weaker than in some apes, possibly due to weaker sexual selection in humans, and points to chimpanzees and gorillas where the female advantage can be substantial.

Why Do These Differences Occur?

The article outlines two primary hypotheses. The heterogametic hypothesis predicts shorter lifespans for the sex with two different sex chromosomes, but it cannot fully explain all cases. The life-history/sexual-selection trade-off hypothesis, which ties longevity to energy, aggression, parental care, and mating systems, aligns well with observed patterns, particularly the large male disadvantages in non-monogamous mammals and the female costs of reproduction in birds. The evidence from multiple taxa supports a view that sex-based longevity is a complex, context-dependent outcome of chromosomes, hormones, competition, care, and ecological risk, rather than a universal rule.

Quality of Life and Hidden Costs

Finally, the piece cautions that longer lifespans do not automatically equate to better living conditions. In humans, longer life for women often accompanies longer periods of ill health; in other species, extended lifespan may come with reduced reproductive capacity or diminished physical performance. The overall message is that female longevity is a widespread but nuanced pattern shaped by an array of genetic, hormonal, social, and ecological factors.