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Human Evolution Driven by Underground Food Sources, New Study Reveals
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HANOVER, NH – July 25, 2025 – A groundbreaking study published today in the journal Science suggests a pivotal shift in the diet of early hominins – towards carbohydrate-rich underground plant organs like tubers, bulbs, and corms – played a key role in their physical evolution, including changes in tooth size and shape. Researchers at Dartmouth College, led by Dr. Laura Fannin and Professor Nathaniel Dominy, propose this dietary adaptation was a “secret sauce” that set hominins apart from other primates and ultimately fueled the advancement of modern humans.
The Dietary puzzle of Human Evolution
for decades, scientists have debated the dietary changes that drove the evolution of hominins, the group including modern humans and our extinct ancestors. Previous theories included increased meat consumption, a reliance on abrasive grasses (graminoids), or a semi-aquatic lifestyle. The Dartmouth team systematically evaluated these hypotheses, focusing on the interplay between behavior, diet, and dental morphology.
- Hominins drank far more water than other primates and savanna animals.
- They adopted a semi-aquatic, hippopotamus-like lifestyle.
- They began regularly eating underground plant organs such as tubers, bulbs and corms.
The research team concluded that the third explanation – the adoption of underground storage organs (USOs) as a staple food source – best explains the observed evolutionary changes. USOs, like potatoes and yams, are packed with carbohydrates and were readily available year-round, offering a reliable food supply even during harsh conditions. Crucially, they were also less accessible too other herbivores, providing a competitive advantage for hominins.
Teeth Tell a Story of Dietary Change
The study analyzed dental remains from various hominin species, revealing a consistent trend: a gradual reduction in tooth size of approximately 5% per 1,000 years, coupled with an elongation of molars. This shift began around 2 million years ago, coinciding with the emergence of species like Homo habilis and Homo ergaster. These species exhibited dental features better suited for processing tougher plant tissues, perhaps including cooked USOs.
The researchers emphasize the ubiquity of graminoids across diverse ecosystems, suggesting early humans could readily exploit these resources wherever they migrated. The study highlights that the ability to efficiently extract nutrients from grass tissues, and especially USOs, may be a defining characteristic of human evolution.
“One of the burning questions in anthropology is what did hominins do differently that other primates didn’t do? This work shows that the ability to exploit grass tissues may be our secret sauce,” Dominy said. “Even now, our global economy turns on a few species of grass – rice, wheat, corn and barley,” he added. “Our ancestors did something completely unexpected that changed the game for the history of the species on Earth.”
Implications for Understanding Human History
This research provides a new framework for understanding the evolutionary pressures that shaped early humans.The consistent availability of USOs may have also facilitated larger brain development by providing a stable energy source. The study also suggests that the development of stone tools, already in use by hominins, was crucial for accessing these underground resources.
Reference: Fannin LD, Seyoum CM, venkataraman VV, et al. Behavior drives morphological change during human evolution. Science. 2025;389(6759):488-493. doi: 10.1126/science.ado2359
This article is a rework of a press release
