Archaeologists believe humans have been collecting crystals for at least 780,000 years for no apparent reason, until now.
While crystals have been discovered at sites containing Homo remains, they were apparently not used as tools, weapons, or jewellery, raising more questions than answers.
However, a new European study has explored what makes crystals so appealing by studying how chimpanzees, one of humans closest living relatives, respond to them.
Professor Juan Manuel García-Ruiz, from Donostia International Physics Center in San Sebastián, said experiments suggested that the attraction to crystals may have deep evolutionary origins that predated modern humans.
“We show that enculturated chimpanzees can distinguish crystals from other stones,” Prof García-Ruiz said.
“We were pleasantly surprised by how strong and seemingly natural the chimpanzees’ attraction to crystals was. This suggests that sensitivity to such objects may have deep evolutionary roots.”
He said humans and chimpanzees split from a common ancestor between six and seven million years ago, and the two species still shared many behavioural and genetic traits.
Prof García-Ruiz said to investigate whether an attraction to crystals might be one of them, researchers gave groups of enculturated chimpanzees access to crystals.
He said the researchers found that the animals’ curiosity was strongest immediately after they encountered the crystal and slowly faded over time, a pattern similar to the way novelty wears off in humans.
“Caretakers later had to trade bananas and yogurt to persuade the chimpanzees to return the crystal.”
Prof García-Ruiz said chimpanzees would also recognize quartz crystals, similar in size to those collected by ancient hominins, mixed into a pile of rounded pebbles.
“Even after the researchers added pyrite and calcite crystals, each with different shapes from quartz, the chimpanzees still recognized and selected the crystal type stones.
“The chimpanzees began to study the crystals’ transparency with extreme curiosity, holding them up to eye level and looking through them,” he said.
Prof García-Ruiz said the team concluded that transparency and geometric shape appeared to be the features that made crystals especially attractive, with those same qualities also explaining why early humans chose to collect them.
He said unlike trees, mountains, rivers, clouds, and animals, which are dominated by curved and branching forms, crystals stood out because of their flat surfaces and straight edges.
“They are the only naturally occurring polyhedral solids, making them unlike almost anything else in the natural landscape. these unusual patterns may have captured the attention of early humans as they tried to understand the world around them.
“Our work helps explain our fascination with crystals and contributes to the understanding of the evolutionary roots of aesthetics and worldview,” Prof García-Ruiz said.
