研究表明，雌性哺乳動物比雄性壽命更長，這與性行為有關 (2/2)

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Female mammals live longer than males because of their sexual behavior, study suggests (2/2)

CNN - By Amarachi Orie

Oct 3, 2025

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Bigger, not better

One theory, the sexual selection hypothesis, suggests that some male animals spend their energy developing traits and behavior to compete for and attract mates, such as changing their physical size, developing big antlers or horns, and fighting to compete for a female. In doing so, they may be “sacrificing their survival,” Colchero said.

Another, the cost of reproduction hypothesis, suggests that carrying and delivering a child, and providing parental care, can come with a survival cost, according to the study.

The scientists found evidence in support of the sexual selection theory, with female mammals living longer than males in species that were non-monogamous — having more than one sexual partner. This suggests that spending too much energy trying to build up your size to find mates, for example, has a “cost,” Colchero said.

However, analyzing data from zoos, the researchers found the opposite trend to what they would have expected under the cost of reproduction theory.

Females with childcare responsibilities tended to live longer than males in zoos. This was the same in the wild, although the researchers said they had less evidence for this.

“This seems to be counterintuitive because, for anyone that has babies, you know that the energy that you put in care — you have to put a lot of energy. And you would imagine that that energy would come at the expense of survival,” Colchero said.

However, he added that it “does make sense” in terms of evolution, since some scientists have argued that the sex doing the caregiving needs to survive longer, especially if the offspring is highly dependent, as the caregiver has to ensure that the child can survive to adulthood and reproduce themselves.

The species in which only the females take on childcare also tend to be species that are polygamous, with the males trying to mate with many females. Therefore, it could also be that the males are at a disadvantage regardless, because they are spending more energy mating, the researchers noted.

“This study expands our knowledge of the complex interplay of factors that contribute to sex differences in adult lifespan, including heterogametic sex determination,” ecologist Zoe Xirocostas, a chancellor’s research fellow at the University of Technology Sydney in Australia, told CNN on Thursday.

While the study lends “further evidence in support of the heterogametic sex hypothesis,” it “mainly considers other evolutionary drivers of sex differences in lifespan that may be just as important, such as parental care and mating system,” Xirocostas, who was not involved in the study added, highlighting the “impressive” breadth of species covered, “including groups with limited coverage in previous studies.”

Biologist Gerald S. Wilkinson, a professor at the University of Maryland, who was not involved in the research, also said the “impressive” study “provides some additional support in favor of the heterogametic sex hypothesis for which sex is expected to have a shorter lifespan.”

“But, I think the more interesting result is that they found strong evidence indicating that the mating system and sexual size dimorphism explain much of the life expectancy variation,” Wilkinson added.

“That is somewhat surprising given that mating systems in zoos are not often typical of what happens in the wild. This result indicates that factors that influence lifespan persist even in controlled environments,” he continued.

Translation

研究表明，雌性哺乳動物比雄性壽命更長，這與性行為有關 (2/2)

（繼續）

更大，並非會更好

一種理論，即性選擇假說，認為一些雄性動物會花費精力發展各種特徵和行為來競爭和吸引配偶，例如改變體型、長出大鹿角或犄角，以及為爭奪雌性而爭鬥。Colchero表示，這樣做可能「犧牲了生存」。

另一種理論:生殖成本假說，認為懷孕、分娩以及提供父母的照顧可能會帶來生存成本。

科學家發現了支持性選擇理論的證據，在非一夫一妻制的物種中，雌性哺乳動物的壽命比雄性更長 - 擁有多個性伴侶。Colchero表示，這表明，花費過多精力來增大體型以尋找配偶是有「代價」的。

然而，研究人員分析了動物園的數據，發現趨勢與他們根據生殖成本理論的預期截然相反。

在動物園中，承擔育兒責任的雌性動物往往比雄性動物壽命更長。在野外也是如此，儘管研究人員表示，他們缺乏這方面的證據。

Colchero說:「這似乎違反直覺，因為對於任何養育幼崽的人來說，你都知道你投入到照顧幼崽上的精力 - 你必須投入大量的精力。而且你會想像，這些精力是以犧牲生存為代價的」。

然而，他補充說，從進化的角度來看，這“確實有道理”，因為一些科學家認為，承擔照顧責任的性別需要存活更長時間，尤其是在後代高度依賴的情況下，因為照顧者必須確保幼崽能​​夠存活到成年並繁殖後代。 

僅有雌性負責育幼的物種，也傾向於實行一夫多妻制, 雄性會試圖與多位雌性交配。因此，研究人員指出，雄性也可能無論如何都處於劣勢，因為它們在交配上花費了更多能量。

澳洲雪梨科技大學校長研究員、生態學家 Zoe Xirocostas 週四告訴CNN:「這項研究擴展了我們對導致成年壽命性別差異的複雜因素相互作用的認識，包括異性配子性別決定」。

未參與這項研究的 Xirocostas 補充道, 雖然這項研究 “提供了進一步的證據來支持異性配子性別假說”，但它“主要考慮了其他可能同樣重要的由進化驅動的壽命性別差異因素，例如父母撫育和交配制度”，他並強調了該研究涵蓋的物種範圍“令人印象深刻”，“包括了先前研究中有限地涉及的物種。”

未參與這項研究的生物學家 Gerald S. Wilkinson 的馬裡蘭大學教授也表示，這項 “令人印象深刻” 的研究為異性配子性別假說提供了一些額外的支持，該假說認為，性預計會縮短壽命。”

Wilkinson 補充道: 「但我認為更有趣的結果是，他們發現了強有力的證據表明，交配制度和性別上的體型差異在很大程度上解釋了預期壽命的差異」。

他繼續說道:「考慮到動物園裡的交配制度通常與野外的情況並不完全一致，這解釋多少有些令人驚訝。這一結果表明，即使在受控環境中，影響壽命的因素仍然存在」。

So, according to a new study, sexual behavior is one reason why female mammals typically live longer than their male counterparts. One interesting result of this research is that there is strong evidence to suggest that the mating system and sexual size dimorphism may explain much of the life expectancy variation.

Note:

1. Heterogametic sex determination (異性配子性別決定) refers to a mode of sex determination where two different types of sex chromosomes are involved, leading to distinct male and female roles in reproduction.