Environmental Shocks Rewrote the Fate of Ancient Cities
For years, archaeologists have debated why the Wari city of Pikillaqta in southern Peru was suddenly abandoned. New research now points to a far less human explanation: earthquakes, followed by a landslide so severe it buried parts of the city under as much as 2.5 meters of debris.
Writing in Geoarchaeology, Briant García of Peru’s Instituto Geológico Minero y Metalúrgico and colleagues examined surviving structures and the surrounding landscape at Pikillaqta, once the Wari’s largest city. Built by more than 5,000 people over more than 12 years, the settlement served for nearly four centuries as a ceremonial and administrative center before being left to ruin around 1,000 years ago. The team argues that around AD900, two powerful earthquakes may have struck in quick succession, triggering a massive landslide that overwhelmed the city. The Wari never recovered.
The finding adds to a growing body of research showing that environmental forces, not only warfare or politics, can determine the course of history. For much of the 20th century, scholars tended to explain the rise and fall of civilizations through conflict, invasion, and state power. New methods are shifting that view, allowing researchers to reconstruct how landscapes, rainfall, and seismic activity shaped human settlement.
A similar reassessment has emerged at Teotihuacan in Mexico. At its height around AD500, the city housed an estimated 150,000 people, making it one of the most populous urban centers on Earth. Papers published in 2024 and 2025 in the Journal of Archaeological Science: Reports suggest that repeated megathrust earthquakes, likely from the Pacific coast, damaged the city’s pyramids and may have accelerated its decline after AD550.
Other studies point to slower environmental pressures. Research published in National Science Review indicates that the collapse of the Shijiahe culture in central China coincided with decades of heavy rainfall, which left land waterlogged and harder to farm. In Western Polynesia, by contrast, changing sea surface temperatures appear to have made the region drier around 1,000 years ago, pushing people from Samoa and Tonga eastward toward wetter islands such as Tahiti, according to a study in Communications Earth & Environment.
Taken together, these cases suggest a broader historical pattern: civilizations do not only fall to armies or internal strife. Sometimes, the decisive force is the ground shaking, the rain failing, or the land itself becoming uninhabitable.
