Evolutionary explanations for the function of sleep


Evolutionary Explanations of the Function of Sleep

What is the Evolutionary approach?

          We know that sleep must be adaptive in some way, otherwise why do all animals do it despite substantial costs?

          Either it provides some vital biological function, or it provides some other benefit.

          The Evolutionary explanations aim to suggest what other benefits might be associated with sleep.

          The evolutionary approach has also been called the ecological approach. It is called ‘ecological’ because it is based on observations of animals in their natural environment;

          ‘Ecology’ is the study of animals in relation to their environment.


          Although all animals sleep, patterns vary:

        Nocturnal / Diurnal

        Amounts of sleep

        Amounts of REM / NREM

        So there are different explanations within the evolutionary perspective


          Energy conservation

          Predator avoidance

          Foraging requirements

          Waste of time

Energy Conservation

          All activities use energy, and animals with high metabolic rates use even more energy.

          Sleep, however, serves the purpose of providing a period of enforced inactivity (therefore using less energy)

In some animals, hibernation is a means of conserving energy. Webb (1982) described this as the hibernation theory of sleep


          Availability of food: animals sleep more when food is scarce (Berger & Phillips 1995).

          Zepelin and Rechtschaffen (1974) - smaller animals, with higher metabolic rates, sleep more than larger animals.

Predator avoidance

          If an animal is a predator, then it can sleep for longer whereas prey species sleep time is reduced as they must remain vigilant to avoid predators.

          if sleep is a vital function then they are best to sleep when least vulnerable.

          Shrews in burrows & bats in caves can sleep more safely than antelopes or zebras on the open savannah


          Could sleep be more risky that quiet alertness? Are you more likely to be eaten if you’re asleep?

          But research support (Allison & Cicchetti 1976; Lesku et al 2006)

        predators have more total sleep time than prey




This is really good but what is the evaluation for the Foraging Requirements bit?



This has great information, thanks 

Danielle Sefu


This is sooo good. definitely helpful for my revison 



good but every point is too short.