Five hypotheses have been developed in attempt to explain selective forces that drive sleep patterns. First, it was proposed that levels of pathogen infection determine the length of sleep cycles. Hypothesis 2 considers correlation between energy utilization and the benefits of sleep. Thirdly, it was seen that genetic regulation is critical sleep expression. Fourth, sleep expression was viewed from a chemical perspective. Finally, it was determined that predation also contributes to mammalian sleep patterns.
Although each hypothesis can be viewed as feasible in selecting for sleep patterns in mammals, hypothesis two is the most significant. As the hypothesis postulates, energetic constraints influence expression of patterns of sleep in a way that the more energy the animal spends, the higher the sleep duration to lower the metabolic rate and conserve energy. This is the most relevant hypothesis that strongly supports the main thesis statement since it is also backed by concrete evidence from authorities that have done extensive studies regarding evolution of sleep. Based on research findings, it is clear that energetic constraints shape the foundation of mammalian sleep.
The physiological control of sleep in both humans and nonhuman mammals is influenced by the consequences of the waking experience (Langford and Cokram 2010). This means that sleep can be used as a valuable tool in assessment of the welfare of mammals. Mammals exposed to stressful activities, painful events and fatigue, experienced prolonged periods of sleep afterwards than animals exposed to less energy consuming events. Therefore, during the activity, animals spend a lot of energy until they become exhausted and since there is no more energy to spend, the animals are triggered to sleep to reduce the metabolic activity (Chaput et al. 2007).
Since most of the research done have only based on a few species of mammals, I recommend that future researchers should cover a wide variety of mammals so that the conclusions made on the selective pressures that influence mammalian sleep patterns could be made with outstanding evidence and little assumptions. Based on the research done, there is a knowledge gap between circadian sleep based rhythms and sleep based on environmental seasonality that need to be examined. More research needs to be done on ecological factors that affect sleep to add more weight to the energetic constraints affecting sleep.