The story begins in 1923, when Scottish geologist George Barbour visited the Nihewan Basin in Yangyuan County, Hebei, and recognized that the ancient lake sediments exposed along the riverbanks were far older than anyone had suspected. Barbour misjudged the age, but his instinct about the site's importance was sound. He invited two French archaeologists -- Pierre Teilhard de Chardin and Emile Licent -- who pushed the age estimate past a million years and, crucially, found that flint tool. The discovery should have revolutionized understanding of early human migration into East Asia. Instead, it was overtaken by a more dramatic find.

Pei Wenzhong's discovery of Peking Man at Zhoukoudian, hundreds of kilometers to the south, captured the world's attention and redirected the scientific community's focus. Wars and revolution further distracted researchers from the Nihewan Basin. Xiaochangliang sat largely unexamined for decades, its potential buried both literally and figuratively. It was not until the 1970s that systematic excavations resumed, and between 1972 and 1978, archaeologists unearthed more than 2,000 stone tools along with bone tools that removed any remaining doubt about the site's authenticity as a Paleolithic habitation.

Dating Xiaochangliang proved technically challenging. Asian Paleolithic sites typically lack the volcanic materials that allow isotopic dating methods used so effectively in Africa. Instead, researchers turned to magnetostratigraphy, which dates geological layers by identifying when the Earth's magnetic field reversed polarity. These reversals, recorded in the orientation of iron minerals within sediments, serve as a geological clock. Using this method, the stone tools at Xiaochangliang were dated to 1.36 million years ago. The tool assemblage includes side and end scrapers, notched tools, burins, and disc cores -- a diverse toolkit suggesting a population well adapted to its environment.

Xiaochangliang turned out to be just one window into the Nihewan Basin's deep past. Archaeologists have now identified 40 sites in the basin dating to approximately one million years or older, making it one of the densest concentrations of early Paleolithic occupation outside Africa. The basin itself, formed by an ancient lake, provided the water, game, and raw materials that sustained human populations across immense stretches of time. From the air, nothing distinguishes the landscape -- gently eroded hills, a river valley, the quiet topography of northern Hebei. But beneath that unremarkable surface lie the tools and traces of people who arrived here more than a million years before anyone would think to look.