Neanderthal bones collected by hyena at Grotta Guattari, central Italy, 66–65 ka: U/Th chronology and paleoenvironmental setting

After eight decades since its discovery in 1939, new investigations have been undertaken at Grotta
Guattari (Latium, central Italy), a coastal cave by the Tyrrhenian Sea coast and one of the iconic sites of
the Italian prehistory, as it yielded an almost complete skull and other remains of Neanderthals. The new
excavations of the innermost and untouched cave deposits resulted in an outstanding amount of
mammal bones, 40 out of which attributable to Neanderthal, including new large portions of cranial
remains. Preliminary taphonomic hints and the collected stratigraphic evidence strongly indicate that
the impressive accumulation of the large mammal bones was the work of spotted hyena, in a period in
which human frequentation was really sporadic or even completely absent. The new acquired U/Th
chronology of Grotta Guattari speleothems provided new constraints for reconstructing the sedimentary
and paleoenvironmental history of the archaeological successions and human remains. The accumulation
of terrestrial sediments started at ~112 ka, immediately after the end of the Last Interglacial sea-level
highstand (~116 ka). However, the hyena frequentation, and thus the bone accumulations, occurred
several thousands of years after and lasted for a very short time interval, precisely between slightly
before 66 ka and 65 ka. The cave became abandoned by hyena after ~65 ka and before ~59 ka, because of
the cave obstruction and/or the altered environmental conditions related to the Heinrich Event 6 (~64
e60 ka). The regional paleoclimatic records indicate severe conditions during the short interval of the
hyena frequentation. In contrast, though providing evidence of open and arid environments, the faunal
assemblage and the pollen from Grotta Guattari reveal that the local conditions were less severe, likely
because of the mitigating effect of the Tyrrhenian Sea. In the framework of the Italian findings, Grotta
Guattari results the richest and better chronologically constrained site of Neanderthal remains, posing it
as one of the rare sites of the European prehistory that allows putting into the context an extraordinary
large sample of the population of Neanderthals, and of other large mammals, in a very narrow and
precisely dated temporal interval of the early Pleniglacial