Reacción a "Hominids used fire more than 700,000 years earlier than previously estimated, according to a study involving Spanish researchers"

The control of fire marked a crucial turning point in human evolution, enabling transformations that spanned from biology to complex social organisation. The use of fire in food processing was fundamental to hominin adaptation, facilitating greater energy extraction, improved digestibility and an increase in the nutritional value of the diet, all of which have been correlated with evolutionary changes in body mass and brain size. Furthermore, the controlled use of fire has been linked to increased cohesion and the geographical dispersal of the genus Homo. Therefore, determining the onset of the controlled use of fire by hominins is a central issue for understanding human evolution, yet identifying the earliest evidence of this is extraordinarily complex.

The article by Marín-Monfort et al. points out that the individual use of the techniques employed to date to detect thermal alterations in sediments, lithics and bones is insufficient. In particular, FTIR, despite being widely used, does not allow for the unequivocal identification of combustion events below approximately 537 °C.

The authors therefore propose a protocol based on the luminescent properties of bones, which offers significant advantages as it is rapid, non-destructive, independent and suitable for analysing large samples. They have verified the validity of the method through systematic comparison with FTIR analyses applied to the same fossils.

The text concludes that the combination of luminescence and FTIR constitutes a robust method for identifying burnt bones, as it allows combustion to be confirmed and distinguished from natural alterations. At Wonderwerk Cave, the results confirm the presence of fire in stratum 10, previously documented, and provide new evidence in stratum 11, where signs of thermal alteration in various materials are observed. Furthermore, the bones showing evidence of thermal alteration at this level are concentrated in specific areas, suggesting localised episodes of combustion.

Although some proposals suggest an association between hominins and fire dating back to around 1.5 million years ago, the most robust evidence of controlled and recurrent use of fire currently dates to around 0.8 million years ago. From a chronological perspective, the lack of precision regarding Stratum 11 at Wonderwerk Cave—which falls within a broad timeframe of between 1.79 and 1.07 million years—prevents these findings from being definitively linked to the onset of controlled fire use or aligned with the earliest stages of the Acheulean (around 2 million years ago). Therefore, if the chronology of stratum 11 were to be refined and it could be linked to the early phases of the Acheulean, the finding would constitute a highly significant contribution to our understanding of human evolution.

In my opinion, the main contribution of the article lies not so much in definitively pushing back the start of controlled fire use, but in the methodological approach it proposes through the use of luminescence as a complementary technique to FTIR for identifying thermally altered bones.

The proposed methodology represents a significant advance, as it could become a very useful tool for identifying the use of fire during the Pleistocene, including at European sites, where there are various proposals regarding the controlled use of fire that have not yet been sufficiently verified through robust analytical protocols.