 As uncertain as the exact dating of the lower jaw of Mauer was until recently, so is the assignment of other fossils to its layer.Such contextual fossils are the only direct evidence for an accurate reconstruction of the habitat of a find.Not until 1991 two sets of core drilling were conducted in the defunct sand mine of Grafenrain and—beginning in 1995, several dozen cubic meters of sand were screened in search of fossil fragments that could shed light on accompanying species.