Article 1 (July 2019): The lizard in your brain needs a blanket even in summer

Most people cover up with sheets or blankets even in summer. But, why?
 
The lizard is why.
              
Somewhere deep in your brain, when you enter Rapid Eye Movement (REM) sleep, the body becomes reptilian, unable to regulate its temperature.
              
According to Atlas Obscura, sleep studies have proved this and it might be one reason why humans use blankets or sheets, even in the summer.
              
The other reason could be behavioral. After all, we are used to coverings. We associate them with sleep. We've been covered at night since infancy.
              
It could be that humans throughout history always wanted coverings, but it's also true that most didn't have them. For centuries, only the very rich had bedding because making a huge linen sheet was expensive. Instead, families, animals, and even strangers, slept together for warmth.
              
After the Middle Ages, more people came to have bedding but it was expensive, accounting for a third of the value of a whole household.  Even until the 1850s in the American frontier, beds were frequently part of a will.
              
Studies of contemporary non-modern societies show that nearly all use some sort of covering, either woven fibers or plant material. This is true even in tropical climates.
              
Lately, weighted blankets have become popular as studies have shown they are associated with higher levels of serotonin and tend to reduce anxiety.