Date Published: January 26, 2017
Publisher: Public Library of Science
Author(s): Fabrizio Marra, Piero Ceruleo, Luca Pandolfi, Carmelo Petronio, Mario F. Rolfo, Leonardo Salari, Michael D. Petraglia.
We revise the chronostratigraphy of several sedimentary successions cropping out along a 5 km-long tract of the Aniene River Valley in Rome (Italy), which yielded six hominin remains previously attributed to proto- or archaic Neanderthal individuals, as well as a large number of lithic artefacts showing intermediate characteristics somewhere between the local Acheulean and Mousterian cultures. Through a method of correlation of aggradational successions with post-glacial sea-level rises, relying on a large set of published 40Ar/39Ar ages of interbedded volcanic deposits, we demonstrate that deposition of the sediments hosting the human remains spans the interval 295–220 ka. This is consistent with other well constrained ages for lithic industries recovered in England, displaying transitional features from Lower to Middle Paleolithic, suggesting the appearance of Mode 3 during the MIS 9-MIS 8 transition. Moreover, the six human bone fragments recovered in the Aniene Valley should be regarded as the most precisely dated and oldest hominin remains ascribable to Neanderthal-type individuals in Europe, discovered to date. The chronostratigraphic study presented here constitutes the groundwork for addressing re-analysis of these remains and of their associated lithic industries, in the light of their well-constrained chronological picture.
Six hominin remains have been recovered since the middle of the 19th century from the Middle Pleistocene sedimentary successions cropping out at four locations (Saccopastore, Casal de’ Pazzi, Ponte Mammolo, Sedia del Diavolo) along a short tract (~5 km) of the Aniene River Valley in northern Rome (Fig 1), the most relevant ones being two skulls of Homo neanderthalensis found in the years 1929  and 1935 . An age ranging from130,000–80,000 years BP was attributed to these skulls, occurring within fluvial gravel beds exposed by quarry excavation at the Saccopastore site, until a recent study  demonstrated that the sedimentary succession in which they were recovered dates back to 250,000 years BP, providing the oldest Italian evidence of H. neanderthalensis. Previous estimation of age was based on the sedimentary deposits being classified as a fluvial terrace of the last interglacial stage, an estimate which was made at the time of the discovery [4, 5, 6]. In contrast,  have shown that the fluvial-lacustrine deposits of Saccopastore correlate with the aggradational succession deposited within the Tiber and Aniene river valleys  in response to the post-glacial sea-level rise during glacial termination 3 (T-3), at the onset of Marine Isotopic Stage (MIS) 7.
The area of Rome is located on the Tyrrhenian Sea margin of Central Italy, SW of the Apennine mountain range, and is crossed by the Tiber and Aniene Rivers (Fig 1). The city center is just downstream of the confluence, whereas the urban area extends onto a hilly landscape, cut by the hydrographic networks of these rivers. Two volcanic districts that were active in the time span 802–36 ka [45, 46], the Colli Albani and the Monti Sabatini, are located SE and NW of the urban area, respectively.
According to their attributions, ranging from proto-Neanderthal (those recovered in the deposits of the Via Mascagni succession) to archaic Neanderthal (the skull from the lowest Saccopastore layer occurring in the Vitinia Formation deposits), the hominin remains associated with the lithic industries considered transitional to the Middle Palaeolithic can be ascribed to early Neanderthal populations, living in the time span 295–220 ka in the Aniene Valley (Fig 11).