Why Can’t Humans Have Naturally Blue Hair?
Human hair cannot be naturally blue because its colour comes from only two pigments: eumelanin, which gives dark shades, and pheomelanin, which gives golden and reddish ones. Every natural hair colour is a mix of the two, and neither can produce blue, green or purple.
Human Brain Facts: Why the Brain Cannot Feel Pain
The adult human brain contains about 86 billion neurons, makes up only about 2% of body mass but uses 20% of the body’s oxygen, and cannot feel pain.
What Is Hindsight Bias? Why We Say “I Knew It All Along”
Hindsight bias is the tendency to see past events as more predictable than they really were. Once we know how something turned out, our brain quietly edits our memories, and we feel that we “knew it all along”.