Excavations had begun at Zhoukoudian in 1921, investigating a number of caves in the limestone there. The remains of around fifteen prehistoric individuals were uncovered, with the first fragments being exposed in 1923. The finds have been dated from roughly 250,000-400,000 years ago.

The pre-war work was directed by Otto Zdansky, then Davidson Black and later by Pierre Teilhard de Chardin and Franz Weidenreich. The first specimens of H. erectus had been found in Java in 1891 by Eugene Dubois, with the Java Man initially being named Pithecanthropus erectus but later transferred to the genus Homo.

All the pre-war finds at Zhoukoudian were lost at sea during transit to the US, forcing subsequent researchers to rely on casts and existing writings from the original discoverers.