Answer: Evolutionary
Step-by-step explanation: The sleeping pattern is highly related with the concept of evolution. The pattern depicts the sleeping technique is due to the activity and inactivity involved in the human life for conserving the energy.
The factor also responsible for sleeping at night is to make sure that the inactivity is present so that the risk of predation can be low.It is also believed that the supply of food is also scarce at that point of time.The dark period considered as night time creates a atmosphere of vulnerability for risk of predation, so adaptability of inactivity is present at darkness.