An ancient basin in Greece that once supported early humans and large animals underwent dramatic environmental changes as ice ages came and went, according to new research. Scientists studying the Megalopolis Basin in southern Greece found that the landscape repeatedly shifted between dry floodplains and lush wetlands over hundreds of thousands of years.
The findings offer new insight into how changing climates shaped the environments available to early human populations between approximately 780,000 and 340,000 years ago.
The study, led by Ines J. E. Bludau, examined ancient sediment layers preserved in the Megalopolis Basin, located in the central Peloponnese. Researchers found evidence of repeated changes in water levels, vegetation, and river activity linked to glacial and warmer periods.
Basin in Greece preserves evidence of climate change
The Megalopolis Basin occupies an important position along a prehistoric migration route connecting different parts of Europe. Scientists believe southern Greece may have provided shelter for early human populations during periods of extreme cold. Previous research has also shown that Greece’s landscape during the Ice Age differed considerably from the frozen conditions experienced farther north in Europe.
To reconstruct the region’s environmental history, researchers examined two sediment cores drilled more than 100 meters deep, along with two exposed geological sections. They studied the composition, grain size, and chemical properties of the sediments. They also analyzed ancient magnetic signals preserved in the deposits to establish their approximate ages.
An ancient Greek basin reveals how Ice Age climate shifts transformed the habitats of early humans.
New research shows how Greeceās Megalopolis Basin repeatedly changed from dry floodplains to lush wetlands between 780,000 and 340,000 years ago. pic.twitter.com/VtlG5pIICY
— Tom Marvolo Riddle (@tom_riddle2025) November 11, 2026
The results revealed alternating layers of river sediments and lignite, a type of soft brown coal formed from accumulated plant material. These layers preserve evidence of two contrasting environments that developed as climatic conditions changed.
During colder and drier periods, rivers periodically spread across the basin, depositing clay, silt, and sand. The surrounding landscape became more open, with shallow water and floodplains supporting relatively limited vegetation. Warmer and wetter periods produced a different environment.
Lakes expanded, marshes developed, and dense vegetation grew along the water’s edge. Plant remains accumulated in waterlogged conditions and eventually formed the thick lignite deposits found today.
Early humans may have found refuge during ice ages
The findings are particularly important because the Megalopolis Basin contains several archaeological sites associated with early human activity. Previous excavations uncovered prehistoric animal remains and stone artifacts at sites dating back about 700,000 years in the basin.
One of the best-documented sites, Marathousa 1, preserves evidence of human presence dating to roughly 430,000 years ago, during a particularly cold glacial period.
Archaeologists previously discovered stone tools associated with the butchering of prehistoric elephants at the site. The findings suggest that early humans used sharp stone flakes to process large animal carcasses. The basin also supported animals such as elephants, hippopotamuses, deer, cattle relatives, and macaques.
Earlier research suggested that local wetlands provided a refuge for plants, animals, and early humans during the severe cold of Marine Isotope Stage 12. Scientists have also identified 430,000-year-old wooden tools at Marathousa 1, highlighting the importance of the basin for understanding early human behavior.
The new study places these discoveries within a much longer environmental record, showing how the surrounding landscape changed before and after that glacial period.
New evidence improves the timeline of ancient habitats
Researchers also identified a revised position for an ancient reversal of Earth’s magnetic field, which occurred about 780,000 years ago. This adjustment helps scientists better match sediment layers across the basin and establish a more reliable timeline of environmental changes.
Although the findings do not directly establish when early humans entered or abandoned the region, they provide important clues about the conditions those populations encountered. The research adds to growing evidence of early human activity in Greece hundreds of thousands of years ago.
The researchers say further studies of ancient pollen, sediments and archaeological remains could help explain how changing climates influenced human movement and survival across southern Greece. The findings strengthen the evidence that the Megalopolis Basin preserved a changing landscape in which rivers, lakes and wetlands repeatedly reshaped habitats during the Middle Pleistocene.
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