The Stone Spheres of Costa Rica

Imagine yourself in southern Costa Rica in the 1930's. You're a digger working for a banana plantation, excavating the shallow tropical soil to make way for another row of agricultural monophyly replacing the once verdant and diverse forest. Your shovel hits something hard, maybe an errant stone in the soil, so your work your shovel around the periphery to no avail. As you continue to dig around the object, you eventually reveal a 2 meter sphere, made entirely of stone. Having grown up in the region, you've heard stories about these stone spheres, known locally as Las Bolas. They're a thousand years old, carved with magic potions, perfectly spherical, and filled with gold. Have you really stumbled upon an ancient and magical relic, or is there a more plausible history for the object you've accidentally started digging up?

This may story sound far-fetched, but it is the sort of thing that happened when southwestern Costa Rica was being developed for agriculture. Hundreds of stones, some only centimeters in diameters others several meters, were uncovered. Some were destroyed to try and find supposedly hidden treasures, others were taken to be put on display in and around the homes of Costa Rica's wealthy elite, and thankfully some were left in place or interred in the Museo Nacional de Costa Rica (or the Costa Rican National Museum) for preservation and study. When they were first discovered there was a brief period of intensive study, followed by a decades long gap until interest was renewed in the stones in the 1970s, leading to their status today as objects worthy of archaeological investigation just like any other impressive mesoamerican relics.

To date, over 300 stones have been found in the Diquís Delta and on Isla del Caño. The Diquís Delta is named for the now extinct Diquís culture that used to inhabit the region. Some of the spheres are made from sandstone or limestone, about a dozen spheres each, the rest of the about 300 known are sculpted from gabbro, all common rocks to the region. Gabbro is an igneous rock that is chemically similar to something like basalt, but instead of cooling at the surface due to a volcanic eruption, gabbro is plutonic, meaning it cools from magma into rock while still in the Earth's crust.

The idea of giant ancient stone spheres first entered popular culture in the film "Raiders of the Lost Ark," when adventurer archaeologist Dr. Indiana Jones attempts to take a gold idol statue from an ancient temple in Peru. He tries to replace the idol with a bag of sand of the same weight so as to not set off any of the elaborate traps left to deter thieves, but misjudges the weight and sets everything off anyways, culminating in him running full tilt away from gigantic rolling ball lest he be crushed. An iconic moment on screen, but in no way representative of the likely role of the spheres in Disquís society.

Myths Surrounding the Spheres

But before we get into what the spheres likely purpose was, we should first examine some of the myths surrounding the spheres. Some of these myths are more outlandish than others such as the spheres being from the fictional island of Atlantis or that the spheres were part of a game played by giants. There are only a handful of these myths that require specific mention and scrutiny. The first, as already referenced above, is that the spheres house great riches, like ancient stone piñatas. It is also claimed that the stones were created using a potion to soften the rock, allowing them to be worked into perfect spheres. Some say that the spheres have petroglyphs, or carved symbols, etched into them that can only be seen when wet.

To go through the myths in order, of all the stones that have been broken open, either on purpose or by accident, none have been anything other than solid rock. A variation on the myth claims that the stones were shaped around a single coffee bean, which is unlikely considering the spheres were probably carved from a larger piece of rock, not formed around a central point, and the fact that coffee wasn't introduced to the new world until 1607 in the Virginian colony of Jamestown.

The idea of using a potion to soften the rock is often supported by work presented in the early 1980s by French archaeologist Joseph Davidovits, whose work focused on how pre-Incan people could have disaggregated, or broken apart, stones using acids derived from local plants. However, the stones in question were calcium carbonate based, like limestone, and thus would respond to acid the same way an antacid tablet responds to your stomach acid, but remember that the majority of the spheres in Costa Rica are gabbro, which is mafic, a type rock made up of silicate minerals rich in magnesium and iron, none of which would be as reactive to acid as would be required to shape them as the legend suggests.

One of the most persistent myths about the stones is their perfect sphericity. It's sort of an argument from antiquity, that ancient peoples had some secret knowledge that allowed them to do something perfectly that we've only recently be able to duplicate with modern scientific techniques. And while the stones display an amazing level of craftsmanship not to be discounted, it is also quite obvious that they are not perfect spheres. Even a cursory inspection of easy to locate photographs of the spheres shows this. Now it is possible, if not probable, that spheres have changed their shape slightly over time due to erosion, but the inability to measure them as their original shape does not provide evidence to claim that they were perfectly spherical at some point in the past. All we can measure is what we have left, and what we have left are not perfect spheres.

Finally, the petroglyphs that can only be seen in the rain. This is sort of an ironic claim since including petroglyphs would then mean that the stones couldn't be perfect spheres in the first place. However, taking the claim at face value, we certainly have found some spheres that include petroglyphs or other carvings. They can be seen while the stone is bone dry, but they likely are easier to see when the stone is wet. Paleontologists use a similar technique when looking at fossil trackways, a quick splash of water can make an impression in the rock much more obvious than looking at it while dry. And while most of the spheres today seem smooth, it is possible that originally shallow petroglyphs could have been lost to the rigors of time and erosion.

Possible Explanations and Archaeological Investigations

The simple fact of the spheres is that they were made by the indigenous peoples of pre-Columbian Costa Rica, likely part of the Diquís culture. They first started being made around the year 600, and continued past the year 1000 but ceased production prior to the arrival of the Spaniards. They represent another impressive example of the craftsmanship of people in that region prior to European contact just like the pyramids of the Maya or the alpine cities of the Inca. Part of the reason these stones became associated with more mysterious origins is because the culture of the Disquís, unlike the Maya or the Aztec, went extinct, so there was less cultural memory to draw upon as to their origin and original purpose, fueling myth and legend.

Further, research into their origin, manufacture, and original purpose was hampered by the fact that they were found on land owned by a corporation concerned with fruit farming, not archeology. And many stones were removed from where they were found so the wealthy could have them on display around their homes and in their gardens, thus destroying all the information about their provenance and original placement within a larger context. You can't really roll a pyramid out of the way just so you can keep planting bananas.

Our current understanding of how the spheres were made is deceptively simple, but no less impressive. Indigenous societies, working without wheels or draft animals, transported stone pieces of up to 15 tons to be sculpted into spheres without metal tools. This would have required a high level of organization, time, and skill to accomplish, and should be recognized for the achievement it was.

That's likely how the spheres were made, but why were they made? And what were they for? One of the most promising explanations as to the true nature of the spheres is that they may have been arranged to mimic the stars in the sky, a terrestrial map of the cosmos, sort of like a tropical spherical Stonehenge. The petroglyphs may have also added information about the stars, mapping constellations right onto the sphere to give extra information to a knowledgeable viewer. But it is equally possible that the spheres were a status symbol for the wealthy and powerful, much in the same way they serve for the wealthy modern Costa Ricans who had the spheres brought to their homes. The best way to answer these questions is through careful continued study and preservation.

The people of modern day Costa Rica are proud of the heritage that their stone spheres represent. And they have every right to be proud, the spheres represent some of the remains of a once impressive and advanced culture in the region they now call home. The problem arises when the spheres are presented as somehow magical or mystical, either through honest belief or as way to entice tourist dollars into the area. Fortunately, with the recent advances in the archeology of in situ sphere sites, and the support of the Museo Nacional de Costa Rica, the tide is shifting in favor of understanding the spheres in their appropriate historical context. The efforts have even borne fruit, as the settlements with emplaced spheres on the Disquís Delta were declared a UNESCO World Heritage Site in 2014.

There are many mysteries still surrounding the stone spheres of Costa Rica, but we have every reason to believe that with proper investigative techniques and scientific examination we will progress in our understanding of the Diquís culture, while still retaining a sense of awe at their artistic and technological accomplishments.

By Ryan Haupt