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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >A unifying model for timing of walking onset in humans and other mammals
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A unifying model for timing of walking onset in humans and other mammals

机译：人类和其他哺乳动物的步行发作时间统一模型

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The onset of walking is a fundamental milestone in motor development of humans and other mammals, yet little is known about what factors determine its timing. Hoofed animals start walking within hours after birth, rodents and small carnivores require days or weeks, and nonhuman primates take months and humans approximately a year to achieve this locomotor skill. Here we show that a key to the explanation for these differences is that time to the onset of walking counts from conception and not from birth, indicating that mechanisms underlying motor development constitute a functional continuum from pre- to postnatal life. In a multiple-regression model encompassing 24 species representative of 11 extant orders of placental mammals that habitually walk on the ground, including humans, adult brain mass accounted for 94% of variance in time to walking onset postconception. A dichoto-mous variable reflecting species differences in functional limb anatomy accounted for another 3.8% of variance. The model predicted the timing of walking onset in humans with high accuracy, showing that this milestone in human motor development occurs no later than expected given the mass of the adult human brain, which in turn reflects the duration of its ontogenetic development. The timing of motor development appears to be highly conserved in mammalian evolution as the ancestors of some of the species in the sample presented here diverged in phylogenesis as long as 100 million years ago. Fundamental patterns of early human life history may therefore have evolved before the evolution of primates.
机译：步行的发作是人类和其他哺乳动物运动发展的一个基本里程碑，但对于决定其时机的因素知之甚少。有蹄动物在出生后数小时内便开始行走，啮齿动物和小型食肉动物需要数天或数周的时间，而非人类的灵长类动物则需要数月的时间，而人类则需要大约一年的时间才能达到这种运动能力。在这里，我们表明，解释这些差异的关键是从受孕开始而不是从出生开始计数的时间，这表明运动发育的潜在机制构成了从出生前到产后生活的功能连续体。在包含24种物种的多元回归模型中，代表11种现存的习惯于在地面上行走的胎盘哺乳动物（包括人类），成年脑质量占到孕后行走开始时间的94％。在功能性肢体解剖学中反映物种差异的二分体变量占变异的3.8％。该模型以高准确度预测了人类行走的时机，表明在人类运动发育的这一里程碑发生的时间不晚于成年人大脑质量的预期，这反过来又反映了其个体发育的持续时间。在哺乳动物的进化过程中，运动发展的时机似乎是高度保守的，因为这里介绍的样本中某些物种的祖先在系统发育中早在1亿年前就出现了分歧。因此，人类早期生命历史的基本模式可能在灵长类动物进化之前就已经进化了。

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