The Turkana are a nomadic population from Kenya who live in one of the hottest places in the world, where 50°C is the norm, and move across parts of East Africa as far as Uganda, South Sudan and Ethiopia. Despite the dry climate, the Turkana drink just 1.5 liters of water a day and feed almost exclusively on animal products, mainly milk, red meat and blood from camels and goats – a normally unsustainable diet that would normally cause several chronic diseases.
A study published in Science analyzed the genome of over 300 members of this population, to try to understand how they manage to stay healthy by drinking so little and eating so many animal products, and discovered that this is due to some genetic adaptations (one in particular).
Dehydrated but healthy. Researchers have documented the lives of these nomadic communities for years, collecting blood and urine samples to monitor their health. Despite drinking just 1.5 liters of water a day (whereas a foreigner would have to drink six, to survive the area’s drought levels), the Turkana were generally healthy and had no chronic illnesses. “90% of the people we analyzed were chronically dehydrated, but healthy: a paradox,” comments Julien Ayroles, one of the authors.
Genetic mutations. In addition to hydration, another problem would appear to be the diet, composed of 70-80% animal proteins, a quantity three times higher than what the WHO already considers at risk for the onset of cardiovascular diseases.
How do the Turkana survive these apparently unhealthy eating and living habits? After analyzing the entire genome of 308 representatives of the community, scientists found the answer: eight modified DNA regions, and in particular a gene called STC1 that is expressed in the kidneys and in many Turkana is chronically upregulated.
Upregulation of STC1 causes the kidneys to retain more water, and the Turkana do not die of dehydration – but not only that: according to the researchers, STC1 could also protect the kidneys from waste products such as urea and uric acid generated by red meat, a food rich in purines. “Particularly in sub-Saharan Africa, where chronic heat stress and water scarcity are increasingly common and kidney disease is on the rise, these genetic discoveries could point to possible therapeutic solutions,” comments Ayroles.
Developmental maladaptation. These genetic mutations, advantageous for a nomadic life in hot and dry regions, become a problem when a member of the Turkana community decides to move to the city and switch to a sedentary life: it is the so-called “evolutionary maladaptation”, which occurs when genetic characteristics that have evolved to be advantageous in a certain place and time are no longer advantageous when the environment (or era) changes.
“Understanding these genetic adaptations will help guide health programs for the Turkana — especially now that some are transitioning from traditional pastoralism to urban living,” concludes Charles Miano, another of the authors.
