According to the latest edition of Nature Genetics, a team of Japanese researchers has discovered in ear wax the smallest form of genetic difference, known as a single nucleotide polymorphism.
They have shown that just one tiny change in DNA can lead to a change in how the body works and how we look.
The Japanese team found that in northern Asia - Japan and China - the genetic alteration that produces hard, white ear wax (as opposed to sticky and yellow) is more common. It's also more common among Native Americans, suggesting they may have originally come from China.
As you go south and west of China into Europe, Africa and the Pacific, the hard ear wax variation becomes rare. It's least common in the Solomon Islands and France, according to the study.
The mutation that led to people having this kind of ear wax must have happened in northern China. As with most mutations that become common in a particular population, it must have given the people with hard wax some advantage.
The researchers think the advantage is linked to the other characteristic they noted in the hard ear wax brigade. Their sweat apparently doesn't smell as much as the sweat produced by people with the sticky variety.
The researchers believe this may have made them more attractive in the cold climates, where the hard wax populations are found. Where people spent long winters confined in small areas and needed to be close to one another to stay warm, those people who were less smelly may have been more attractive to potential mates.
Our obsession with body odour is a fairly recent phenomenon. Strong scents are used by many animals to signal readiness for breeding and to attract mates, so it seems odd that we evolved in the opposite direction.
It may be that in a cold, humid region, hard ear wax protects ears more effectively than sticky wax.
Ear wax is an important part of the ear's defences against intruders - insects, dirt and other foreign bodies - that can damage the hearing mechanism.
However, when people move from one environment to another, particularly from a dry climate to a humid one, their ear wax can hold water, and form plugs that block the canal. If the plug expands, it can cause ear pain and hearing loss.
Some people need to have their ears syringed out to prevent hard plugs forming and damaging their ears. This is the only way to have ears cleared and it should only be done when a doctor is satisfied that there is no infection or any other problem causing the blockage.
Never stick a cotton bud or any other object in your ear canal. If you have a big wax plug, it will only push it further down, making it harder to remove.
The most simple treatment is to use oil drops (olive oil is good enough) to soften the wax plugs for a week or so. Then ask your doctor to check your ears and syringe the wax out if necessary.
If you have a fever, dizziness, severe pain, vomiting or marked hearing loss, get your ears checked immediately.