The time between Palaeolithic hearths.

Resolving the timescale of human activity in the Palaeolithic Age is one of the most challenging problems in prehistoric archaeology. The duration and frequency of hunter-gatherer camps reflect key aspects of social life and human-environment interactions. However, the time dimension of Palaeolithic contexts is generally inaccurately reconstructed because of the limitations of dating techniques1, the impact of disturbing agents on sedimentary deposits2 and the palimpsest effect3,4. Here we report high-resolution time differences between six Middle Palaeolithic hearths from El Salt Unit X (Spain) obtained through archaeomagnetic and archaeostratigraphic analyses. The set of hearths covers at least around 200-240 years with 99% probability, having decade- and century-long intervals between the different hearths. Our results provide a quantitative estimate of the time framework for the human occupation events included in the studied sequence. This is a step forward in Palaeolithic archaeology, a discipline in which human behaviour is usually approached from a temporal scale typical of geological processes, whereas significant change may happen at the smaller scales of human generations. Here we reach a timescale close to a human lifespan.

An experimental approach to the preservation potential of magnetic signatures in anthropogenic fires.

Archaeomagnetic and rock-magnetic methods are of great value in the identification of archaeological fire, especially in Palaeolithic sites where evidence is usually scarce, ambiguous or poorly preserved. Although taphonomic processes can significantly modify Palaeolithic combustion structures, the extent to which such processes affect the magnetic record remains unknown. Here we report the results of an archaeomagnetic study involving five, two-to-five-year-old experimental combustion structures in open-air and cave settings. Some of these combustion structures involved post-combustion human actions such as trampling and relighting. Our results show pseudo-single domain (PSD) magnetite as the main magnetic carrier. Wood ash layers of combustion structures are the most magnetic facies followed by thermally altered sediments constituting the combustion substrates. A decreasing magnetic concentration pattern in depth was observed as a function of temperature. Positive correlation was found between good-quality directional data and macroscopically well-preserved combustion structures. Partial thermoremanent magnetization (pTRM) was the main magnetization mechanism identified in the combustion substrate facies. These data coupled with partial thermomagnetic curve experiments show the potential of these methods to estimate maximum temperatures of the last combustion event. Relightings show very good directional results, but they cannot be identified because the time between them is not enough to statistically distinguish directional variations of the local Earth´s magnetic field. The substrate sediment of an intensively trampled combustion structure yielded reliable archaeomagnetic directions. The results are discussed in terms of magnetization preservation potential and the effects of taphonomic processes on the archaeomagnetic record.

Age and date for early arrival of the Acheulian in Europe (Barranc de la Boella, la Canonja, Spain).

The first arrivals of hominin populations into Eurasia during the Early Pleistocene are currently considered to have occurred as short and poorly dated biological dispersions. Questions as to the tempo and mode of these early prehistoric settlements have given rise to debates concerning the taxonomic significance of the lithic assemblages, as trace fossils, and the geographical distribution of the technological traditions found in the Lower Palaeolithic record. Here, we report on the Barranc de la Boella site which has yielded a lithic assemblage dating to ∼1 million years ago that includes large cutting tools (LCT). We argue that distinct technological traditions coexisted in the Iberian archaeological repertoires of the late Early Pleistocene age in a similar way to the earliest sub-Saharan African artefact assemblages. These differences between stone tool assemblages may be attributed to the different chronologies of hominin dispersal events. The archaeological record of Barranc de la Boella completes the geographical distribution of LCT assemblages across southern Eurasia during the EMPT (Early-Middle Pleistocene Transition, circa 942 to 641 kyr). Up to now, chronology of the earliest European LCT assemblages is based on the abundant Palaeolithic record found in terrace river sequences which have been dated to the end of the EMPT and later. However, the findings at Barranc de la Boella suggest that early LCT lithic assemblages appeared in the SW of Europe during earlier hominin dispersal episodes before the definitive colonization of temperate Eurasia took place.