News summary produced by Claude AI
Archaeologists have found crystals at multiple archaeological sites containing remains of early human relatives, with evidence indicating deliberate collection of these stones approximately 780,000 years ago. Unlike typical artifacts, these crystals were not fashioned into tools, weapons, or worn as adornments, prompting researchers to investigate what made them valuable to ancient hominins.
A study released in Frontiers in Psychology examined whether chimpanzees, humanity’s closest living relatives, might provide insight into this behavior. Researchers at facilities in Spain conducted experiments with two groups of enculturated chimpanzees, presenting them with crystals alongside ordinary stones and mixed collections. In initial trials, the animals consistently showed strong preference for crystals over regular rocks, carefully manipulating them by rotating and tilting them to examine different surfaces. The chimpanzees’ interest followed patterns similar to human novelty responses, with curiosity diminishing over time, though caretakers eventually had to offer food incentives to retrieve the crystals.
A second experimental phase tested whether the animals could identify smaller quartz crystals resembling those collected by ancient humans. When researchers mixed these crystals into piles of rounded pebbles, the chimpanzees selected them within seconds. The animals continued discriminating between different crystal types even when pyrite and calcite varieties were introduced, displaying marked curiosity about their transparency properties. One individual exhibited particularly notable behavior by transporting and sorting crystals separately from ordinary stones.
Researchers attributed the animals’ attraction to the geometric properties unique to crystals, specifically their flat surfaces, straight edges, and transparency. These characteristics distinguish crystals from most natural forms in the environment, which typically feature curved or branching structures. The team suggested that early humans may have found these same unusual geometric patterns appealing as they developed understanding of their surroundings.
The study acknowledged limitations, noting that participating chimpanzees were acculturated to human environments and that future research should include less-habituated populations. Researchers also indicated that individual personality differences among animals warrant further investigation in explaining variations in crystal attraction.