Through a collaboration between U.S. and Kenyan researchers and Turkana communities of northern Kenya, scientists have uncovered key genetic adaptations underlying survival in hot and dry environments, revealing how natural selection has enabled this pastoralist population to thrive in a challenging landscape.
A new analysis of Turkana genomes through a collaboration between US and Kenyan institutions shows how the activity of key genes has changed over millennia to allow them to thrive in extreme desert conditions. The comprehensive study, published in Science, reveals how the Turkana people have evolved extraordinary physiological adaptations to survive in their harsh homeland, where water scarcity and extreme heat have shaped their lifestyle.
The Turkana Way of Life
The Turkana homeland stretches across a vast arid landscape in Northern Kenya where shade is rare and water even rarer. While their nomadic existence takes them around East Africa—into Uganda on the west, South Sudan on the northwest and Ethiopia on the north—this is one of the most arid regions of the world. Rainfall arrives in short, unpredictable bursts, and in this environment, securing enough water for themselves and their herds of goats and camels is a daily chore. The journey to fetch water can take several hours each day, often across terrain that is hot and devoid of vegetation.
The traditional pastoralist diet reflects both resourcefulness and adaptation to scarcity: for those adhering to a nomadic pastoralist lifestyle, it is estimated that 70–80% of their nutrition comes from animal sources, mostly milk, blood, and meat. This reliance is a common solution among pastoralist societies around the world, in environments where crops cannot grow and markets may be far away on foot.
Through years of documenting the Turkana community's lifestyle and studying blood and urine samples to assess their health, researchers found a striking paradox: "About 90% of the people we assessed were dehydrated but generally healthy." Ayroles said.
"The Turkana have maintained their traditional way of life for thousands of years, providing us with an extraordinary window into human adaptation," said the project co-PI, Prof. Julien Ayroles, a faculty member at the University of California, Berkeley.
Genomic Discoveries Through Community Partnership
After consultation with the communities' elders, area chiefs and local health officials, the team asked for permission to sample the communities' DNA. Working with the Turkana community, the researchers sequenced 367 whole genomes and analyzed over 7 million genetic variants to identify regions showing evidence of natural selection.
The genomic analysis found eight regions of DNA that had undergone natural selection, but one gene, STC1, stood out with exceptionally strong evidence of selection. STC1 is expressed in the kidneys and plays two vital roles that directly reflect the ecological challenges of both arid living and pastoralism. First, it helps the body conserve water by responding to antidiuretic hormone, allowing the Turkana to concentrate their urine and retain more water. Second, it may also play a role in protecting the kidneys from the waste generated by purine-rich foods like red meat. These waste products, such as urea and uric acid, must be filtered by the kidneys and in many people, too much dietary purine can lead to gout; a problem that appears to be rare among the Turkana.
Ancient Climate, Modern Genetics
Intriguingly, the timing of these genetic adaptations appears to coincide with the aridification of northern Africa, suggesting that as the climate became increasingly dry about 5,000 years ago, natural selection favored genetic variants that enhanced survival in desert conditions. This finding provides a compelling example of how human populations have evolved in direct response to major environmental changes. The genetic analyses show that these changes are also present in neighboring groups, including the Rendille, who live in this arid environment. "This research demonstrates how our ancestors successfully adapted to dramatic climate shifts through genetic evolution," noted Dr. Epem Esekon, the County Executive for Health and Sanitation in Turkana County, Kenya.
When Evolution Meets Urbanization
But the story doesn't end in the desert. As more Turkana migrate to towns and cities, a striking pattern emerges: the very genetic traits that aid survival could now carry hidden costs. This phenomenon, known as evolutionary mismatch, occurs when adaptations shaped by one environment become liabilities in another.
By comparing biomarkers and gene expression in the genomes of city-dwelling Turkana compared to their pastoral kin, the researchers found an imbalance of gene expression that may predispose them to chronic diseases, such as hypertension or obesity, which the researchers have also found to be more common in urban settings, where diets, water availability, and activity patterns are radically different.
"With more people shifting from rural to urban lifestyles, we are also seeing a change in disease patterns," said the Acting Director General of the Kenya Medical Research Institute (KEMRI), Prof. Elijah Songok.
"Understanding these adaptations will guide health programs for the Turkana—especially as some shift from traditional pastoralism to city life," said Charles Miano, one of the study's coauthors and a graduate student at KEMRI in Nairobi.
The study has health implications for many traditional cultures in Africa and around the world that are having to adapt to rapidly changing environments or adopt urban lifestyles. Evolutionary mismatch likely leads to high rates of "lifestyle" diseases around the world, such as diabetes, coronary artery disease and high blood pressure.
"This study highlights how working with transitioning populations can lead to new models for understanding how present-day environments interact with past adaptations to potentially impact modern day disease risk," added Amanda Lea, co-PI of the ongoing study and an Assistant Professor at Vanderbilt University.
The Turkana Health and Genomics Project: A Partnership in Discovery
This story began not in a laboratory, but around desert campfires. Many of the questions this research addresses were generated during long meetings with the Turkana community, facilitated by the Turkana Health and Genomics Project (THGP), a long-term collaboration between Kenyan and U.S.-based researchers. From its earliest days, the project has centered on the co-production of knowledge, combining genomic science with traditional ecological and anthropological expertise. The research agenda emerged from dialogue with Turkana elders, scientists, and community members, conversations about health, diet, and change, often shared in the evening around a camp fire.
"Working with the Turkana has been transformative for this study," said Sospeter Ngoci Njeru, one of the THGP's leaders and deputy director of KEMRI's Centre for Community Driven Research. "Their insights into their environment, lifestyle and health have been essential to connecting our genetic findings to real-world biology and survival strategies."
Lessons for a Changing World and Giving Back
As the world faces rapid environmental change, the Turkana's story offers both inspiration and practical insights. For generations, this community has developed and maintained sophisticated strategies for surviving in a challenging and variable environment, knowledge that becomes increasingly valuable as climate change creates new survival challenges globally.
The research team is now creating a podcast in the native Turkana language that will not only share the study's findings in accessible ways but also will offer the community practical health considerations that arise with rapid lifestyle transitions, combining scientific insights with knowledge from within the community. Based on conversations with Turkana study communities, the study findings resonate with people's perceptions about their capacity to go without water for long periods, but they also noted that other pastoralists in the region. like the Rendille, Samburu, Borana, Merille, Karimojong, and Toposa, are likely to share this adaptation due to living in similarly arid environments.
"I am deeply inspired by the fact that this work places the Turkana and sub-Saharan Africa at the forefront of genomic research, a field where indigenous populations have historically been underrepresented," Miano said.
"Worldwide, indigenous communities like the Turkana are essential partners in advancing our knowledge of human resilience," said Dr. Dino Martins, Director of the Turkana Basin Institute. "Their experience provides lessons for how climate and environmental changes continue to shape human biology and health."
The study appears online Sept. 18 in the journal Science.
