PLOS ONE2013-11-01 6:53 AM

Energetic Consequences of Human Sociality: Walking Speed Choices among Friendly Dyads 人类社会能量选择结果:两人同行步行速度的选择

Abstract Research has shown that individuals have an optimal walking speed–a speed which minimizes energy expenditure for a given distance. Because the optimal walking speed varies with mass and lower limb length, it also varies with sex, with males in any given population tending to have faster optimal walking speeds. This potentially creates an energetic dilemma for mixed-sex walking groups. Here we examine speed choices made by individuals of varying stature, mass, and sex walking together. Individuals (N = 22) walked around a track alone, with a significant other (with and without holding hands), and with friends of the same and opposite sex while their speeds were recorded every 100 m. Our findings show that males walk at a significantly slower pace to match the females’ paces (p = 0.009), when the female is their romantic partner. The paces of friends of either same or mixed sex walking together did not significantly change (p>0.05). Thus significant pace adjustment appears to be limited to romantic partners. These findings have implications for both mobility and reproductive strategies of groups. Because the male carries the energetic burden by adjusting his pace (slowing down 7%), the female is spared the potentially increased caloric cost required to walk together. In energetically demanding environments, we will expect to find gender segregation in group composition, particularly when travelling longer distances. 论文摘要 研究表明个体拥有一个最佳的步行速度-一个给定距离下使得能量消耗最小的速度。因为这个最佳步行速度会随着体重和下肢长度变化而变化,也与性别有关,在随机选定的人群样本中男性的最佳步行速度普遍较快。这潜在的在男女混合的行走群体中形成了一个能量两难处境。在该实验中我们研究了形形色色的不同个体同行时对步行速度的选择,比如不同身形,体重,性别等等。我们记录了每百米距离中,个体(N=22)沿着轨道独自行走,和另一个步行速度明显不同的个体一起走(分别是俩人握住手走和不握住手走),以及换成和同性或异性朋友一起走等各种情形时的步行速度。我们的研究结果显示当同行的异性同伴为自己情侣时,男性明显降低了步行速度。同行的俩人不管是同性或异性朋友步行速度变化都不大(P>0.05)。由此可见,这一显著的步行变化看起来只局限发生在情侣同行时。这些发现对群体的移动性和繁殖策略都具有深远影响。因为男性担负起了自我步行速度的能量调节责任(减速约7%),女性在同行时就避免了额外的卡路里消耗。在那些特别苛求能量的情况中,尤其是像进行远距离迁徙时,我们会发现在群体组成中将出现性别分化隔离的现象。

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