5,000 years ago, people living in Spain may have been documenting family lineages

A study published in the European Journal of Archaeology suggests that the Late Neolithic and Copper Age engraved slate plaques found throughout the Iberian Peninsula may have functioned as one of the earliest non-verbal forms of genealogical records. According to Phys.org, these plaques could document a person's origin and their link to a notable ancestor.

Since the 1800s, around 1,626 hand-sized stone or slate plaques have been discovered in tombs across the Iberian Peninsula, dating from the Late Neolithic and the Copper Age, approximately 3200 to 2200 BCE. The plaques feature delicate engravings of geometric patterns, including zigzags, triangles, and horizontal lines, and are typically covered with thin geometric designs. Phys.org reports that these patterns may have originated from earlier cultural traditions, such as drawings on clothing or body painting.

Many theories have been proposed regarding the purpose of these plaques, ranging from protective amulets to children's drawings of owls. However, their function has not yet been clearly elucidated. Phys.org notes that only 4% of the plaques bear motifs resembling eyes or a nose, making the theory that they represent mother goddesses or ancestors less likely.

The new study proposes that these engraved plaques may have been used by elites to symbolize and affirm their lineage or belonging to an important clan, similar to coats of arms in heraldry. According to Phys.org, the number of lines or engraved motifs—called "registers"—represented the genealogical distance from a founding ancestor. For example, an individual born of the "zigzag clan" and four generations removed from that clan's founder may have a slate with four zigzag registers at its base.

To test their hypothesis, the scientists analyzed 657 plaques, focusing on aspects such as design, geographical distribution, and connection with the sizes of graves. Particular attention was paid to the number of horizontal registers on the tablets, which researchers believe could record important information requiring precision. Professor Katina Lillios, who led the study, explains, "This indicated to me that the number of horizontal lines was not just an aesthetic feature but something that had to be done correctly." As reported by Phys.org, this observation was sparked by the study of one particular plaque in the Museu Geológico in Lisbon in 2003.

"This was a plaque that had engravings on two sides; on one side was what appeared to be a complete draft or sketch, and on the other side was a finished plaque," Lillios described the plaque. "What was interesting was that the two sides had different numbers of horizontal lines; these horizontal lines divide up the base of a Classic plaque." Encouraged by this observation, Lillios advanced the idea that the ancient plaques recorded precise information that needed to be correctly documented. "Sensing that this plaque was indeed a mistake with a correction helped give me the confidence to move the project forward and develop the hypothesis that the plaques were recording some kind of information that had to be recorded correctly," she added.

The researchers found a correlation between the number of registers on the tablets and the distance from Alentejo, the earliest slates' region of origin. As the distance from the Alentejo region increased, the number of registers on the tablets grew, which may indicate successive generations moving away from the main center. Phys.org reports that this finding confirms that the registers could symbolize genealogical or temporal distance from a founding ancestor established in the Alentejo.

Additionally, the study found a positive correlation between tomb size and the number of plaques, with larger tombs housing more individuals with tablets. As larger, more opulent tombs required more labor to build, it is likely that the individuals interred in these tombs came from rich or elite families. "The fact that not everyone at death was accorded a plaque tells me that this was something for a select group," Lillios added. 

The plaques may also have served to organize social aspects such as marriages, the transmission of property, or the right to be buried in a prestigious collective tomb."I sometimes imagine that these collective tombs were like the community archives, which people could consult when important decisions had to be made," Lillios said.

However, archaeogenetic studies could not be used to prove these hypotheses as most individuals buried with slates do not have well-preserved skeletal remains. "We do not see the plaques' designs found in much earlier material culture, such as ceramics," Lillios stated. "The big problem we have is that these tombs are collective tombs used often over a long period of time, so the bodies and objects placed with them are often highly disturbed. But conceivably, a relatively undisturbed site could be found in the future."

Lillios suggested that these designs may have evolved naturally before becoming genealogical records. "So, at the beginning, there could have simply been families or lineages that had a particular design associated with them (the triangle clan, the zigzag clan, etc.), and that over time, someone decided that these designs could be manipulated to generate more precise information, much in the way that European heraldry works."

Phys.org, Gazeta.ru, Lenta.ru, and GEO France reported on the study, among other websites.

This article was written in collaboration with generative AI company Alchemiq