PASS THE MELATONIN: Circadian Clock Signal Weakens With Age. “This result reminds me of the vicious cycles that drive much of aging. Deterioration of sleep quality reduces the repair that happens to the body as we sleep. This accelerates aging, including aging of components that regulate sleep.”

This may have been group-adaptive in the old days, though. Old people — too weak to do the hard day’s work — were up at night when the workers were sleeping, meaning that someone was more likely to notice marauding enemies, dangerous animals, fires, etc. Now, not so much.