Groundbreaking research examining 7,000-year-old mummies from Chile's Atacama Desert has revealed that prehistoric hunter-gatherers possessed significantly smaller brain volumes than modern populations, suggesting centuries of nutritional hardship in one of Earth's most unforgiving environments. The study, recently published in Scientific Reports, analyzed 68 ancient skulls from the remarkable Chinchorro culture and found their average intracranial volume measured 12 percent less than contemporary Chileans. This discovery sheds new light on how extreme environmental conditions shaped human development in prehistoric South America.
The Chinchorro people inhabited the coast of the Atacama Desert between 7,500 and 3,500 years ago, creating the world's oldest known artificially mummified remains - predating Egyptian mummification by millennia. Using advanced CT scanning technology, researchers from Chilean and international institutions measured the cranial volumes of these ancient individuals, comparing them with both pre-Hispanic agricultural populations and modern Chileans, according to IFLScience. The findings revealed that Chinchorro males possessed an average intracranial volume of 1,390.65 cubic centimeters, while females averaged 1,247.65 cubic centimeters - substantially smaller than their modern counterparts.
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Chinchorro mummies at the San Miguel de Azapa museum in Chile, with clay masks and other alterations to their appearance. (Servicio Nacional del Patrimonio Cultural)
Marine Diet and Nutritional Limitations
The Chinchorro culture's subsistence strategy relied almost exclusively on marine resources, with isotopic analysis confirming that approximately 90 percent of their diet came from fish, mollusks, and marine mammals. While the ocean provided stable protein sources, this narrow dietary range likely contributed to nutritional deficiencies during critical developmental periods.
"Early-life malnutrition has been consistently associated with reduced brain volume and cognitive impairments, highlighting the critical importance of adequate energy and nutrient intake during neurodevelopmental windows," the researchers noted in their study published in Nature Scientific Reports.
The hyper-arid Atacama Desert, where annual rainfall can measure less than one millimeter, offered virtually no terrestrial food resources. This environmental constraint forced the Chinchorro to develop remarkable adaptations for coastal living, but it also meant their children grew up without access to the diverse nutrients available to later agricultural societies or modern populations. Based on skeletal analysis, researchers calculated that average Chinchorro males stood approximately 161 centimeters tall, while females measured about 151 centimeters - notably shorter than present-day Chileans.
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Chinchorro mummy heads from an archaeological site in Arica, Chile, approximately 9,500 years old. ( Zorka Ostojic Espinoza/CC BY 2.0)
Agricultural Transition Made Little Difference
Surprisingly, the study revealed that the transition from hunter-gatherer to agricultural lifestyles around 4,000 years ago produced minimal changes in brain size. Pre-Hispanic farmers who cultivated C₃ and C₄ plants while continuing to exploit marine resources showed an average intracranial volume of only 1,336.57 cubic centimeters - barely larger than their Chinchorro predecessors. This finding challenges assumptions about the biological benefits of agricultural adoption in prehistoric populations.
The research team suggested that while farming introduced new food sources, the quality and quantity of nutrition may not have improved substantially for centuries. Archaeological evidence indicates that early agricultural communities in the region faced their own challenges, including interpersonal violence over scarce resources and continued reliance on marine protein. Only in the modern era, particularly during the 20th century, did dramatic improvements in public health, sanitation, and nutrition trigger measurable increases in both stature and cranial volume among Chilean populations.
The harsh landscape of the Atacama Desert, one of the driest places on Earth. (Public Domain)
Modern Nutrition Drives Biological Change
The study's most striking finding concerns contemporary populations rather than ancient ones. Modern Chilean males now possess average intracranial volumes of 1,594.41 cubic centimeters—more than 200 cubic centimeters larger than Chinchorro males. Female Chileans show similar gains, averaging 1,390.19 cubic centimeters compared to the ancient 1,247.65 cubic centimeters. These dramatic increases correlate directly with 20th-century improvements in living conditions, according to Phys.org.
"While transitions in prehistoric subsistence strategies did not produce significant changes in either height or intracranial volume, the 20th century marked an inflection point," the study authors concluded.
The notable increase in stature observed during this period - approximately 5 centimeters in women and 5.5 centimeters in men - coincides with improvements in nutrition, particularly increased intake of dairy and animal proteins, as well as broader gains in public health, sanitation, and education.
The research team emphasized that these findings demonstrate the powerful influence of environmental and nutritional factors on human development. The well-preserved mummified remains from the Atacama Desert, protected by extreme aridity for millennia, provided an unprecedented opportunity to track biological changes across more than 7,000 years of human history. The study utilized non-invasive CT scanning to preserve these irreplaceable archaeological treasures while extracting valuable data about cranial morphology and estimated brain volumes.
This groundbreaking research adds another chapter to our understanding of the remarkable Chinchorro culture, whose sophisticated mummification practices and adaptation to extreme environments continue to fascinate archaeologists worldwide. The findings underscore how modern advances in nutrition and healthcare have fundamentally altered human biology in ways that thousands of years of cultural evolution could not achieve.
Top image: Chinchorro mummies on display at the San Miguel de Azapa museum, 12 km from Arica, Chile. These are among the oldest artificially preserved human remains in the world. Source: Heretiq /CC BY-SA 2.5
By Gary Manners
References
Arnold, P., 2025. Modern life explains why people in Chile are taller and have larger brains. Phys.org. Available at: https://phys.org/news/2025-11-modern-life-people-chile-taller.html
Sepúlveda, M. et al. 2025. Intracranial volume variation in Chinchorro mummies: a comparative study with pre-hispanic farmers and contemporary Chilean populations. Scientific Reports. Available at: https://www.nature.com/articles/s41598-025-25186-y
Taub, B., 2025. Why Did Prehistoric Mummies From The Atacama Desert Have Such Small Brains? IFLScience. Available at: https://www.iflscience.com/why-did-prehistoric-mummies-from-the-atacama-desert-have-such-small-brains-81666
