Richard A. Cerutti | USGS Science

USGS2018

Holen et al. reply

Contrary to our hypothesis that the Cerutti Mastodon (CM) site represents a 130,000-year-old archaeological site, in the accompanying Comment Ferraro et al . argue that the site formed through ‘common’ geological and taphonomic processes. As a source for the cobbles that we interpreted as hammerstones and anvils, they postulate a previously unrecognized alluvial fan, later removed by fluvial winnowing that somehow left our five cobbles, refitting flakes, and fragments of stone, mastodon bone and teeth in place. There is no sedimentological or geomorphic evidence of an alluvial fan, and their scenario leaves unexplained a number of taphonomic features, including the two discrete concentrations in which were found cobbles, refit stones and bones, impact-fractured bones, side-by-side femoral heads and a tusk oriented vertically.

Nature↗

USGS2017

A 130,000-year-old archaeological site in southern California, USA

The earliest dispersal of humans into North America is a contentious subject, and proposed early sites are required to meet the following criteria for acceptance: (1) archaeological evidence is found in a clearly defined and undisturbed geologic context; (2) age is determined by reliable radiometric dating; (3) multiple lines of evidence from interdisciplinary studies provide consistent results; and (4) unquestionable artefacts are found in primary context 1,2 . Here we describe the Cerutti Mastodon (CM) site, an archaeological site from the early late Pleistocene epoch, where in situ hammerstones and stone anvils occur in spatio-temporal association with fragmentary remains of a single mastodon ( Mammut americanum ). The CM site contains spiral-fractured bone and molar fragments, indicating that breakage occurred while fresh. Several of these fragments also preserve evidence of percussion. The occurrence and distribution of bone, molar and stone refits suggest that breakage occurred at the site of burial. Five large cobbles (hammerstones and anvils) in the CM bone bed display use-wear and impact marks, and are hydraulically anomalous relative to the low-energy context of the enclosing sandy silt stratum. 230 Th/U radiometric analysis of multiple bone specimens using diffusion–adsorption–decay dating models indicates a burial date of 130.7 ± 9.4 thousand years ago. These findings confirm the presence of an unidentified species of Homo at the CM site during the last interglacial period (MIS 5e; early late Pleistocene), indicating that humans with manual dexterity and the experiential knowledge to use hammerstones and anvils processed mastodon limb bones for marrow extraction and/or raw material for tool production. Systematic proboscidean bone reduction, evident at the CM site, fits within a broader pattern of Palaeolithic bone percussion technology in Africa 3,4,5,6 , Eurasia 7,8,9 and North America 10,11,12 . The CM site is, to our knowledge, the oldest in situ , well-documented archaeological site in North America and, as such, substantially revises the timing of arrival of Homo into the Americas.

California↗