Newspapers’ claims are a red hairing

By Marie Rogers

Recent news articles have claimed that red haired people may become extinct. The gene for red hair is recessive, which means both parents have to have it for their child to be born with red hair. This story makes the rounds every few years, perhaps because it feels intuitive that if a gene is recessive and only present in 1-2% of the population, it may naturally die out. But this is not how genetics works.

You may know about the behaviour of recessive genes from learning about how the genes for eye colour are passed on. A recessive gene can be present in a person who is a ‘carrier’ without it showing in their appearance. Both parents have to carry the recessive gene for there to be a chance of them passing it on to their child. However, two brunettes can make a redhead as long as they are both carrying the recessive red hair gene.

Gingers have soulsRecessive genes do not get “bred out” of the population, even if very few people show the gene in their appearance. For the recessive red hair gene to die out, every redhead would have to stop reproducing along with every person carrying the gene, who would not even necessarily know they carried it!

A recent article in the Independent claims that warmer weather may cause redheads to become extinct. It notes that redheads are more susceptible to skin cancer, and claims that the colouring originally evolved to allow as much vitamin D exposure as possible in cloudy areas of the world (e.g. Scotland).

Regardless of the reasons already stated, this is a poor explanation of the way evolution works. Even if red hair and pale skin were a disadvantage in a warming planet, this would have to affect the birth rate of redheads to have any impact on the gene.

Skin cancer is a terrible disease and its incidence is increasing, however, it is unlikely to impact on rates of reproduction. This is because it tends to develop later in life, past the age at which people usually have children.

For a gene to become extinct there must be strong selection pressures against it. When there is no particular environmental pressure either promoting or supressing a gene, such as hair colour genes, there is more likely to be variation in the population.

Evolutionary change happens over timescales hard for the human brain to comprehend. If an article says that a gene will be extinct “by 2060” you can safely assume it contains bad science.

 

 

Image: Gingers have souls by Mendhak under Creative Commons License

 

Advertisements