All birds and mammals sleep, along with many fish, amphibians and reptiles. Scientists study sleep intensively, but they are still not sure exactly what is, and most especially what it is for. There are many contradictions. Babies of almost all species sleep far more than adults, yet in some marine mammals such as killer whales, new born babies don’t sleep at all for the first month of life. Some birds (as well as Dolphins) can sleep with one half of their brains, while the other remains awake. For the rest of us, sleep is a period of unconsciousness which usually occupies around one third of our day. Science continues to argue over it’s purpose, but what is agreed is that sleep is absolutely essential to health. (more…)