Fig. 2: Ridge plot of normalized burial wealth values across societies.

The ridge plot is based on min-max normalized burial wealth values, which range from 0 to 1. Consequently, the kernel density estimation (KDE) curves are truncated to ensure their maximum and minimum values are 1 and 0, respectively. For the periods, YZL Youziling, QJL Qujialing, SJH Shijiahe, XJWJ Xiaojiawuji, PTS Pengtoushan, TJG Tangjiagang, DX Daxi.