School of Life and Health Sciences, University of Roehampton, Holybourne Avenue, London, SW15 4JD, UK.
Department of Biology, University of Ottawa, Ottawa, ON, Canada.
J Hum Evol. 2022 Oct;171:103229. doi: 10.1016/j.jhevol.2022.103229. Epub 2022 Sep 15.
In mammals, trait variation is often reported to be greater among males than females. However, to date, mainly only morphological traits have been studied. Energy expenditure represents the metabolic costs of multiple physical, physiological, and behavioral traits. Energy expenditure could exhibit particularly high greater male variation through a cumulative effect if those traits mostly exhibit greater male variation, or a lack of greater male variation if many of them do not. Sex differences in energy expenditure variation have been little explored. We analyzed a large database on energy expenditure in adult humans (1494 males and 3108 females) to investigate whether humans have evolved sex differences in the degree of interindividual variation in energy expenditure. We found that, even when statistically comparing males and females of the same age, height, and body composition, there is much more variation in total, activity, and basal energy expenditure among males. However, with aging, variation in total energy expenditure decreases, and because this happens more rapidly in males, the magnitude of greater male variation, though still large, is attenuated in older age groups. Considerably greater male variation in both total and activity energy expenditure could be explained by greater male variation in levels of daily activity. The considerably greater male variation in basal energy expenditure is remarkable and may be explained, at least in part, by greater male variation in the size of energy-demanding organs. If energy expenditure is a trait that is of indirect interest to females when choosing a sexual partner, this would suggest that energy expenditure is under sexual selection. However, we present a novel energetics model demonstrating that it is also possible that females have been under stabilizing selection pressure for an intermediate basal energy expenditure to maximize energy available for reproduction.
在哺乳动物中，通常报道雄性个体的特征变异大于雌性个体。然而，迄今为止，主要只研究了形态特征。能量消耗代表了多种身体、生理和行为特征的代谢成本。如果这些特征主要表现出更大的雄性变异，或者如果它们中的许多特征没有表现出更大的雄性变异，那么能量消耗可能会通过累积效应表现出特别高的更大的雄性变异。能量消耗的性别差异变化尚未得到充分探索。我们分析了一个关于成年人能量消耗的大型数据库（1494 名男性和 3108 名女性），以研究人类是否在能量消耗的个体间变异程度上进化出了性别差异。我们发现，即使在统计学上比较相同年龄、身高和身体成分的男性和女性，男性的总能量消耗、活动能量消耗和基础能量消耗的个体间变异更大。然而，随着年龄的增长，总能量消耗的变异减少，由于这种情况在男性中发生得更快，因此，尽管仍然很大，但在年龄较大的组别中，更大的雄性变异的幅度会减弱。总能量消耗和活动能量消耗的男性变异更大，可以用男性日常活动水平的更大变异来解释。基础能量消耗的男性变异更大，这是值得注意的，可能部分解释为能量需求器官的大小存在更大的男性变异。如果能量消耗是女性在选择性伴侣时间接感兴趣的特征，这将表明能量消耗受到性选择的影响。然而，我们提出了一个新的能量学模型，表明女性也可能受到稳定选择压力的影响，以保持中间基础能量消耗，从而最大限度地为繁殖提供能量。
