Freiberg Andrew S
Penn State Health, Department of Pediatrics, Penn State Hershey Medical Center, Hershey, PA, US.
J Circadian Rhythms. 2020 Mar 30;18:2. doi: 10.5334/jcr.189.
Although sleep is ubiquitous, its evolutionary purpose remains elusive. Though every species of animal, as well as many plants sleep, theories of its origin are purely physiological, e.g. to conserve energy, make repairs or to consolidate learning. An evolutionary reason for sleep would answer one of biology's fundamental unanswered questions. When environmental conditions change on a periodic basis (winter/summer, day/night) organisms must somehow confront the change or else be less able to compete in either niche. Seasonal adaptation includes the migration of birds, changes in honeybee physiology and winter abscission in plants. Diurnal adaptation must be more rapid, forcing changes in behavior in addition to physiology. Since organisms must exist in both environments, evolution has created a way to force a change in behavior, in effect creating "different" organisms (one awake, one asleep) adapted separately to two distinct niches. We sleep to allow evolving into two competing niches. The physiology of sleep forces a change to a different state for the second niche. The physiological needs for sleep are mechanisms that have evolved to achieve this goal.
尽管睡眠无处不在，但其进化目的仍然难以捉摸。虽然每种动物以及许多植物都会睡眠，但其起源理论纯粹是生理性的，例如为了保存能量、进行修复或巩固学习。睡眠的进化原因将回答生物学中一个基本的未解决问题。当环境条件周期性变化（冬季/夏季、白天/黑夜）时，生物体必须以某种方式应对这种变化，否则在任何一个生态位中竞争的能力都会减弱。季节性适应包括鸟类的迁徙、蜜蜂生理的变化以及植物的冬季落叶。昼夜适应必须更快，除了生理变化外还会迫使行为发生改变。由于生物体必须在两种环境中都生存，进化创造了一种迫使行为改变的方式，实际上创造了“不同的”生物体（一个清醒，一个睡眠），分别适应两个不同的生态位。我们睡眠是为了能够进化以适应两个相互竞争的生态位。睡眠的生理机能促使进入第二种生态位时转变到一种不同的状态。睡眠的生理需求是为实现这一目标而进化出的机制。
