Chimpanzees Share Humans’ Fascination With Crystals. It Could Hint At The Roots Of Symbolic Thought

Chimpanzees Hoard Crystals Just Like Our Ancestors Did. Scientists Think They Know Why

Nearly 800,000 years ago, long before religion, art, or philosophy, human ancestors were picking up crystals and carrying them home. Not as tools. Not as weapons. Not as ornaments. Just kept, and apparently treasured. A new study published in Frontiers in Psychology suggests the answer to why has less to do with culture than with something far older: primate biology.

When researchers gave chimpanzees access to the same kinds of crystals ancient humans collected, the animals responded almost identically. They ignored nearby rocks. They sorted crystals out of mixed piles of pebbles in seconds. One chimp held a small quartz crystal inches from his eye for more than 15 minutes, rotating it slowly, studying the light. Another kept a large crystal for two days and refused to give it up until researchers offered a ransom of bananas and yogurt.

If chimpanzees, who split from the human lineage roughly six to seven million years ago, share this pull with modern people, it suggests the fascination may stem from perceptual tendencies shared across primates. And according to the researchers, it may have done more than drive ancient collecting. It may have lit the earliest spark of symbolic thought.

Why Humans Have Been Collecting Crystals for Nearly a Million Years

Excavations at China’s Zhoukoudian site turned up 20 quartz crystals alongside Homo erectus remains dated to at least 600,000 years ago, possibly more than 800,000. Other sites in India, Austria, and South Africa show the same pattern. Early modern humans in what is now the Kalahari Desert were collecting calcite crystals 105,000 years ago.

None show evidence of being carved, sharpened, or worn. Researchers have long read this as one of the earliest signs of symbolic thinking, placing value on an object for reasons beyond survival. The question is why crystals, specifically, triggered that response, and whether it predates humans entirely.

What Nine Chimpanzees Revealed About Crystal Attraction

To find out, a team led by Juan Manuel García-Ruiz of the Donostia International Physics Center in Spain worked with nine adult chimpanzees at the Rainfer sanctuary near Madrid. Two social groups. No prior exposure to crystals.

In the first experiment, a large transparent quartz crystal and a similarly sized sandstone rock were mounted on separate pedestals in the outdoor enclosure. Cameras ran all day. All five chimps in one group interacted with the crystal repeatedly. None gave the rock more than a passing glance. The alpha female pried the crystal loose and carried it inside. Getting it back took hours and the animals’ favorite foods.

Follow-up experiments scattered crystals, including transparent quartz, translucent calcite, and shiny metallic pyrite cubes, into piles of roughly 20 ordinary pebbles. Every time, the chimps pulled the crystals out and left the pebbles behind. One chimp, Guillermo, did it using his mouth in seconds. Another, Sandy, went further: after collecting items from several piles, she sorted everything into two groups on a wooden platform, pebbles on one side, all three crystals on the other.

Geometry, Transparency, and the Primate Pull Toward Crystals

Two properties kept emerging as attractors: shape and transparency. When opaque and transparent crystals were both available, the chimps took both. When well-formed crystals were mixed with rounded, polished quartz without flat faces, they again took both. Neither property alone explains the behavior. Both seem to matter.

As the researchers write, euhedral objects, meaning those with clearly defined flat faces, have almost no parallel in the natural world. Aside from crystals, straight lines and precise geometric shapes are largely absent from nature. In a savannah world built almost entirely on curves, a crystal was a genuine anomaly. Sharp angles, flat faces, precise symmetry, none of it existed anywhere else in nature.

Transparency was equally strange. Water is about the only naturally transparent thing ancient humans regularly encountered, which may explain why the Greek word for crystal, “cryos,” translates roughly as super-frozen water. A stone that looked like water but stayed solid was, in the early hominin world, unlike anything else.

Chimp Yvan made the fascination with light concrete. After pulling a small quartz crystal from a pebble pile, he held it inches from his eye for more than 15 minutes, rotating it repeatedly. Sanctuary staff confirmed he had no vision problems. Researchers took it as genuine curiosity about how light moves through solid matter.

How Crystal Collecting May Have Sparked Symbolic Thought

Researchers note that symmetrical stone tools appear much later in human history than the earliest crude stone tools, with a notable leap in precision around 500,000 years ago, roughly when crystal collecting became widespread. They suggest that repeated encounters with crystal geometry might have helped early hominins notice and reproduce patterns, though the study cannot test that idea directly.

What it does argue is that crystals may have been among the first objects to prompt hominins to value something for reasons beyond survival. That capacity is widely considered the foundation of symbolic thought, and by extension, of art, ritual, and religion.

If wild apes show the same response in future studies, the roots of symbolic thought may run much deeper, and much further back, than most researchers have assumed.

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