Blondes, they say, have more fun. But redheads have a definite edge when the going gets tough, according to scientists.
A gene found in flame-haired women means they are better at coping with pain than blondes or brunettes.
The research could help to explain the strong character of famous redheads down the ages – from Cleopatra, Nell Gwynne and Florence Nightingale to Lulu.
The gene, called Mc1r, is linked to ginger hair and fair skin. But while it gives women a higher pain threshold, it does not have the same effect on their male counterparts, researchers found.
Scientists at McGill University in Montreal believe this is because there are subtle differences in the way the male and female brains process pain.
Normally when humans and other mammals experience discomfort, the body reacts to dull it by releasing natural substances which are similar to medications such as morphine.
Professor Jeffrey Mogil and his colleagues decided to mimic this effect by giving women doses of an artificial painkiller and seeing how effective it proved.
They chose four groups of ten volunteers. Each was given the painkiller, pentacozine, and then subjected to varying degrees of pain.
The painkilling effect on redheaded women was three times as great as in the other groups.
The findings could help doctors make better choices when it comes to prescribing pain medication, Professor Mogil said. Pinpointing relevant genes should help doctors tailor dosages of drugs to each patient’s needs.
Beyond the sex differences, it was clear that there are genetic differences which affect how well a drug will work, he added.
The results of the study are published this week in Proceedings of the National Academy of Sciences.
In other recent research, scientists have found that ginger hair and a pale skin offer an important advantage in the survival game.
Redheads boast a secret genetic weapon which enables them to fight off certain debilitating and potentially deadly illnesses more efficiently than blondes or brunettes.
A pale complexion permits more sunlight into the skin, where it encourages the production of vitamin D. This helps to prevent rickets, a disease which progressively weakens bone structures, and the lung disease tuberculosis, which can be fatal.
Red hair is mostly found in northwest-Europe and there are far more redheads in Scotland and Ireland than anywhere else. Between 7 and 10 per cent of Scots have red hair.
The downside of pale skin, however, is that it increases the risk of skin cancer in areas with strong prolonged sunlight.