The study of ancient art provides information as to when cognition first appeared in human evolution. Because of its durability, this is usually restricted to carvings on stone or other durable surfaces in habitable caves. One such cave was formed by intense wave action and is located on the Mediterranean coast of Gibraltar, a small promontory situated at the southern extreme of the Iberian Peninsula. Recently a large international group including Joaquin Rodriguez-Vidal, Francesco d’Errico, and Clive Finlayson determined that engravings in the stone of this cave were made by Neanderthals [Reference Rodriguez-Vidal1].

An engraving was found on a flat area of about 300 cm². It consisted of eight deeply engraved lines forming an incomplete criss-cross pattern, obliquely intersected by short thin lines. The engraved pattern was strikingly different from natural fissures that were also found on exposed surfaces in the cave.

Figure 1 Engraving made by Neanderthals in a Gibraltar cave required an estimated 200 strokes of a stone tool.

Using light optical microscopy and scanning electron microscopy, Rodriguez-Vidal et al. were able to determine that a series of grooves were made with unique movements of a stone tool tip (Figure 1). Experimenting with a series of likely stone tools, they estimated that the engraving would require about 200 deliberate blows of a hammer-like device on the stone tool. Specifically, some of the lines were engraved with a robust stone point by repeatedly passing the tool tip into the groove in the same direction. Remarkably it was apparent that no accidental marks were made outside the pattern, and there was only one place where the end of a line was fringed. This suggests that a reasonably skilled person, or group of people, made the engraving. Other experiments ruled out that the marks were made for a utilitarian purpose, such as a stone where animal skins were processed.

Rodriguez-Vidal et al. estimated that the engraving was made about 39,000 years ago. This is the earliest time that this was done (terminus ante quem in anthropologic terminology), and at that time it is known that Neanderthals inhabited Iberian Peninsula and modern humans did not. The significance of this to the field of anthropology is enormous! The production of purposely made engraved or painted designs on cave walls is recognized as a major cognitive step in human evolution. This had been considered to be restricted to modern humans. The engraving in this cave represents the first directly demonstrable case in which a technically elaborated, consistently and carefully made non-utilitarian engraved abstract pattern, whose production required prolonged and focused actions, has been observed on the bedrock of a cave. For the first time, Rodriguez-Vidal et al. demonstrated the capacity of Neanderthals for abstract thought and expression.