One thing that came to mind when I read about mass burial was a ritual disposal. For example, in Japan, there are ritual disposals of daruma dolls, ema, and om

One thing that came to mind when I read about mass burial was a ritual disposal. For example, in Japan, there are ritual disposals of daruma dolls, ema, and omamori (protective charms). If the body parts were part of a type of a prayer/charm fad, it makes sense that there would be some kind of ritual disposal -- it seems like bad mojo to throw out someone's uterus, for example.