Archaeologists have found crystals at numerous sites, including those of the Homo tribe, suggesting that relatives of early humans intentionally collected these rare stones 780,000 years ago. What makes this behavior so interesting is that crystals were not used as tools, weapons, or jewelry. So why were they considered worth preserving?
New research published in frontiers of psychology Provide possible answers. Researchers in Spain explored why crystals are so fascinating by studying how chimpanzees, one of our closest living relatives, react to crystals. Their experiments suggest that our fascination with crystals may have deep evolutionary roots that predate modern humans.
“We showed that civilized chimpanzees can distinguish crystals from other stones,” said lead author Juan Manuel García-Ruiz, Ikerbasque Research Professor of Crystallography at the Donostia International Physics Center in San Sebastian. “We were surprised at how strong and natural chimpanzees’ attraction to crystals was, suggesting that sensitivity to such objects may have deep evolutionary roots.”
Chimpanzees show an unexpected fascination with crystals
Although humans and chimpanzees diverged from a common ancestor 6 to 7 million years ago, the two species still share many behavioral and genetic traits. To investigate the possibility that fascination with crystals was one of them, researchers gave two groups of enculturated chimpanzees at the Rainfur Foundation access to crystals. The first group included Manuela, Guillermo, Ivan, Yaqui and Toti. The second group included Gombe, Lulu, Pascual and Sandy.
In the first experiment, the researchers placed a large crystal, known as a monolith, next to a similarly sized regular rock. At first, both objects caught the chimpanzees’ attention, but the crystals soon became the clear favorite, and the regular rocks were largely ignored.
After removing the crystal from the stand, the chimpanzees carefully examined it, rotating and tilting it to view it from different angles. Ivan the chimpanzee eventually picked up the crystal and deliberately brought it back to his dormitory.
The researchers found that the animals’ curiosity was strongest immediately after encountering the crystals, and gradually waned over time. This is the same pattern in which novelty wears off in humans. The managers then had to trade bananas for yogurt in order to convince the chimpanzees to return the crystals.
Chimpanzees quickly extracted crystals from ordinary stones.
The second experiment tested whether chimpanzees could recognize small crystals, the same size as those collected by ancient humans. I mixed it into a pile of 20 round pebbles and within seconds a crystal was picked out.
Even after the researchers added pyrite and calcite crystals, which have a different shape than quartz, the chimpanzees still recognized and selected the crystal type of stone.
“The chimpanzees began to study the transparency of the crystals with great curiosity, lifting them up to eye level and looking through them,” García-Ruiz said.
The animals continued to examine the crystals for hours.
A chimpanzee named Sandy exhibited particularly interesting behavior. She took both the pebbles and crystals in her mouth and carried them to a wooden stand where she sorted them into separate groups.
“She isolated three types of crystals with different clarity, symmetry, and luster from all the pebbles. This ability to recognize crystals despite their differences surprised us,” Garcia-Ruiz said.
Chimpanzees do not normally carry objects in their mouths, so the researchers suggest that Sandy may have been hiding the crystals, a behavior that could indicate she considered them valuable.
What crystals meant to early humans
The researchers said future studies should consider personality differences, but they did not investigate whether certain chimpanzees are naturally more interested in crystals than others.
“There’s Don Quixote and Sancho. There’s the idealist and the realist. Some people are attracted to the transparency of crystals, and others are interested in their scent and whether they’re edible,” García-Ruiz pointed out.
The researchers also noted that the chimpanzees in the study were used to living around humans and regularly encountered objects that would not exist in the wild. They argue that similar experiments should eventually be conducted in less cultured apes, ideally in wild populations.
By combining observations from both experiments, the researchers concluded that transparency and geometric shape are the characteristics that make the crystals particularly attractive. These same properties may also explain why early humans chose to collect them.
Unlike trees, mountains, rivers, clouds, and animals, which are dominated by curved and branched shapes, crystals are distinguished by their flat surfaces and straight edges. These are the only polyhedra that occur in nature and are unlike most others in the natural landscape. Researchers suggest these unusual patterns may have caught the attention of early humans as they sought to understand the world around them.
“Our research helps explain our fascination with crystals and contributes to understanding the evolutionary roots of aesthetics and worldviews,” García Ruiz concluded. “We know that crystals have been in our hearts for at least six million years.”
