Humans were not the only ones captivated by gemstones. Chimpanzees were also found to be drawn more to crystals with mostly smooth, gem-like faces than to irregular stones. The sample size was small, making it hard to generalize, but the findings raise the possibility that a love of gemstones is an instinct shared across primates.
A team led by Professor Juan Manuel García-Ruiz at the Donostia International Physics Center in Spain said on the 5th in the international journal Frontiers in Psychology that "chimpanzees, the primates closest to humans, showed a tendency in experiments to be more attracted to crystals than to ordinary stones."
◇Had to get a banana to return the crystal
Humanity's love of gemstones runs deep. Crystals were excavated alongside archaic human remains at a site dating back 780,000 years. There were no traces of processing them into useful objects like weapons, tools, or even ornaments. So why collect crystals? Spanish scientists found evidence in animal experiments that an instinct for gemstones existed before humans evolved.
García-Ruiz's team, specialists in crystallography, conducted two experiments at a chimpanzee sanctuary in Spain. First, they placed a sandstone and a quartz crystal of similar size on two pedestals. The researchers named this experiment MONOLITH.
They chose the name to reflect their aim of exploring how preferences for gemstones evolved. In the 1968 film 2001: A Space Odyssey, the MONOLITH appears as a rectangular stone pillar–shaped machine used by an alien species to monitor and steer human evolution. Early humans in the film showed curiosity toward the MONOLITH.
In this experiment, the chimpanzees also showed more interest in crystals with angular, flat faces like a MONOLITH than in stones. They took them home and hid them. The chimpanzees sometimes lifted the crystals to eye level and peered through them, apparently checking their transparency. The chimpanzees used the crystals as a medium of exchange. The keepers could retrieve the crystals only after giving the chimpanzees bananas and yogurt.
In the second experiment, they hid a quartz crystal of a size similar to those from archaeological sites among 20 round pebbles. The chimpanzees picked out the quartz within seconds. Quartz crystals are hexagonal prisms. They likewise found pyrite crystals, which are cubic with a metallic luster, and calcite crystals, which are rhombohedral and milky white.
◇Drawn to crystals since 6 million years ago
Humans and chimpanzees diverged from a common ancestor 6 million to 7 million years ago and evolved separately. If chimpanzees are drawn to crystals, humans, whose genes and behavior are similar, likely were as well. García-Ruiz said, "Humans have kept crystals in their hearts for at least 6 million years."
The researchers said curiosity about crystals stems from their distinctive appearance. Most natural objects are round or concave, while crystals are uniquely solid with straight lines and flat surfaces. García-Ruiz noted, "When early humans tried to make sense of their surroundings, they would have been attracted to unfamiliar forms like the chimpanzees in this experiment," adding, "We believe crystals helped humans invent geometry and awaken abstract thinking."
Experts called the results intriguing but warned against overgeneralization. Michael Haslam at Historic Environment Scotland said, "The chimpanzees in this experiment seem to share with humans a trait of being attracted to shiny and translucent objects," but added, "It is hard to generalize because the chimpanzees are in a sanctuary rather than in the wild, and the sample size is small."
The Spanish team also acknowledged the study's limits. García-Ruiz said, "We plan to run the same experiment with wild chimpanzees," adding, "Unlike their counterparts raised among people, wild chimpanzees know nothing of polyhedra or Euclidean geometry, which makes the experiment far more interesting."
References
Frontiers in Psychology (2026), DOI: https://doi.org/10.3389/fpsyg.2026.1633599