Archaeologists classified the pits into two major types: large-scale and medium — or small-scale. Most wild animals were found in the smaller pits, while larger pits contained horses — often two to eight — as well as elephants and human remains.

"The Shang people seemed to have dug pits based on the size and number of animals each pit needed to hold," says Li Zhipeng, a researcher at the Institute of Archaeology at the Chinese Academy of Social Sciences, who leads the zooarchaeological analysis. "Large pits suited multiple horses. One or two wild animals required smaller spaces."

The combinations of species likely carried specific ritual meanings, though further study is needed to clarify them, says Li.

"Zooarchaeological analyses show many of the animals were wild, but since 29 bronze bells have been unearthed from the pits, many found near the necks of wild animals, we believe they were raised by the Shang royal family, rather than captured shortly before sacrifice," says Li Xiaomeng, a member of the archaeological team at Yinxu.

Li Zhipeng says the bells are a sign of animal management, probably attached to track animals' movements.