Reacción a "Evidence found that humans made fire 400,000 years ago"

To propose today that fires as ancient as the one published by Ashton and colleagues—dated to 400,000 years ago—were caused by humans and not by natural factors, such as lightning strikes, requires collaboration between various disciplines and the application of complex and precise techniques that allow us to affirm, without a doubt, an anthropogenic origin. And that is precisely one of the strongest points of this work: the combination of different methodologies, which gives it great solidity.

First, the visible evidence was analysed: the colouring of the sediments due to high temperatures; the presence of stone tools with evidence of exposure to fire; and, above all—because this is what sets this study apart—the appearance of two fragments of pyrite.

For fire to exist, fuel (material capable of burning), an oxidiser (oxygen) and a source of ignition (sufficient energy to initiate combustion) are required. At sites of this age (400,000 years), it is most common to find remains of fuel, such as charcoal, ashes or burnt bones. However, it is much more difficult to find evidence of the elements capable of generating the energy needed to start a fire. At Barnham, this aspect is documented by the presence of pyrite. The name of the mineral itself provides a clue to one of its traditional uses: in classical Greek, πῦρ (/pyr/) means “fire”. Pyrite has been used since time immemorial as a flint stone and, when struck against flint, produces enough heat to ignite certain plant materials. Although we have evidence of much older fires—such as those at the Cueva Negra del Estrecho del Río Quípar site in Caravaca de la Cruz (Murcia), dating back nearly 900,000 years—these could have been of natural origin. This does not mean that humans did not use them; they did, but there are doubts about their ability to control the entire process. Thus, they probably took advantage of natural fires, “transported” them and used them in their settlements. In the case of Barnham, this mystery is solved: the presence of pyrite indicates that humans 400,000 years ago had the necessary knowledge to generate fire ex novo. Until the publication of this research, this ability had only been confirmed 50,000 years ago.

This evidence is compelling in itself. A few decades ago, finding burnt elements at a site of this age would have been sufficient to confirm their human origin. Today, this is no longer the case: it is necessary to resort to a wide range of methods and techniques. Consequently, the research team decided to go beyond what the eye can see and resorted to highly resolutive techniques to define anthropogenic fires at the Barnham site and distinguish them from natural fires recorded at the same site. Soil micromorphology, which allows the composition of stratigraphic facies to be studied at a microscopic level with great precision, and physical and chemical analyses, which have made it possible to estimate temperatures above 700 °C and establish that human dwellings were recurrent.

The implications of the study are numerous, and some have been highlighted by the British Museum team. Between 500,000 and 300,000 years ago, multiple transformations took place: human groups with larger brains, new ways of carving stone, an increase in big game hunting as a means of obtaining resources, cooking food, etc., all of which, according to the authors, is linked to growing social complexity, which leads us to propose something truly thought-provoking: the Ju/'honsai—who live in the Kalahari Desert and until relatively recently maintained a hunter-gatherer lifestyle—often gather around the fire to share invented stories, rumours, gossip and conversations that stimulate the imagination. It is therefore possible that this type of social exchange has been with us for 400,000 years.

This work, however, has overlooked an aspect that, in my opinion, may be relevant: the possible contribution of fire to settlement in climatically colder regions thanks to its ability to generate heat and protection.

This study does not present any significant limitations that should be taken into account.