Abilities and conditions that very few people have.
13 oddities.
About 1% of people of Northern European descent carry two copies of a broken gene that makes them almost immune to the most common form of HIV. A bone marrow transplant from one such donor produced the first cure of HIV.
A chimera is one person made of two sets of cells with different DNA. It happens when two embryos fuse in the first days of pregnancy. Most chimeras never find out. A few discovered it when a DNA test said they were not the mother of their own children.
A tiny number of people are born unable to feel pain. Single-gene changes switch off their pain nerves. It is not a superpower. Injuries go unnoticed, and most people with it are badly hurt in childhood.
Some children can keep a detailed picture of an image in view for a short time after it is taken away. The ability fades by the teenage years. A true photographic memory in adults has never been confirmed.
Most adults can hold their breath for 30 to 90 seconds. Trained freedivers manage over 11 minutes, and over 24 minutes after breathing pure oxygen. One group of sea nomads has evolved larger spleens for diving.
A few dozen people worldwide can recall what happened on almost any date of their adult lives, in detail and without effort. Their memory for other things, such as lists or numbers, is ordinary.
Some blind people find their way by making sharp tongue clicks and listening to the echoes. Brain scans show the echoes are processed in the visual cortex. Sighted people can learn a basic version in a few weeks.
Birds, turtles, and many other animals sense Earth's magnetic field. Whether humans do is unsettled. A 2019 experiment found brain-wave changes in response to a rotating field, but nobody has shown a conscious magnetic sense.
About 1 in 60 people feel a touch on their own body when they watch someone else being touched. The brain system that mirrors other people's actions appears to be turned up too high.
About 1 in 10,000 people can name or sing any musical note without hearing a reference note first. It runs in families and is far more common in people who started music lessons very young.
A very small number of people with a developmental disability or brain injury have one extraordinary skill, such as instant calendar calculation, drawing a city from memory, or playing a piece of music after one hearing.
A small number of people need only 4 to 6 hours of sleep a night, wake without an alarm, and feel fine. Several gene variants that cause it have been found. Most people who sleep that little are simply sleep-deprived.
About a quarter of people taste bitter compounds far more strongly than everyone else. They have more taste buds and a particular version of one gene, and they often dislike coffee, dark greens, and grapefruit.