A study has found that a common genetic variant linked to migraine headaches may have proliferated because it helped early humans migrating from Africa adapt to cold weather. Stock image
Within the last 50,000 years, groups of people left the warmer climates of Africa and moved to chillier areas in Europe and Asia, as well as other parts of the world.
The study, done by Felix Key of the Max Planck Institute based in Germany, examined TRPM8, a gene that codes for the only known receptor that enables a person to detect and respond to cool and cold temperatures.
‘This colonization could have been accompanied by genetic adaptations that helped early humans respond to cold temperatures’ said Aida Andres, who supervised the study.
The researchers discovered that a variant of the gene has become increasingly common in people living in higher latitudes over the last 25,000 years.
Scientists had previously identified the variant as being strongly associated with migraines.
They discovered that 88 percent of people with Finnish ancestry carried the variant, compared with only 5 percent of people with Nigerian ancestry.
The genetic variation was, and still is, rare in Africa, but is now common outside of the continent.
Researchers analyzed genetic data from more than 1,200 modern people around the world, as well as from 79 ancient people who lived between 3,000 and 8,500 years ago.
‘This study nicely shows how past evolutionary pressures can influence present-day phenotypes,’ said Key.
HOW DID NORTHERN EUROPEANS EVOLVE TO HAVE LIGHT SKIN?
Common European traits like pale skin evolved relatively recently in central and southern Europe. Researchers had long assumed that skin lightened as humans migrated from Africa and the Middle East into Europe around 40,000 years ago.
Experts had speculated that shorter day lengths and a sun lower in the sky favoured lighter skin, which more easily synthesised vitamin D. But a groundbreaking 2015 analysis of the genomes of 83 prehistoric Europeans showed that populations in Europe about 8,000 years ago were still mixed and diverse.
Traits commonly associated with modern Europeans, such as tallness, the ability to digest milk, and lighter skin tone, only became ubiquitous in Europe relatively recently. Experts found that about 8,500 years ago, early hunter-gatherers in central and southern Europe, including Spain, Luxembourg, and Hungary, had darker skin.
They lacked versions of two genes, called SLC24A5 and SLC45A2. These genes were responsible for ‘depigmentation’, and hence pale skin, in Europeans today. In the far north of Europe, where low light levels favoured pale skin, the team found hunter-gatherers had a lighter complexion.
Two light-skin gene variants, SLC24A5 and SLC45A2, were found in seven people from the 7700-year-old Motala archaeological site in southern Sweden. A third gene found in the group, HERC2/OCA2, has been linked to blue eyes and may also contribute to blonde hair and light skin.
The research shows that, contrary to previous theories, Europe was still a diverse continent up to at least 8,000 years ago, showing that pale skin developed in central and southern Europe much later than first thought.
Migraines, characterized by throbbing and pulsating pain, impact millions of people in the US and they are hard to treat because no one really know what causes them.
Several non-genetic factors increase the risk of migraines, including being middle-aged, female, high stress levels, and low socio-economic status.
However, migraines are also highly heritable.
According to the World Health Organization, migraines have the lowest prevalence in Africa and the highest occurrence in Europe.
In the US, migraine prevalence has consistently shown to be higher in European-Americans than African-Americans.