Stone Spheres of Costa Rica

"2: Giant Stone Spheres of Costa Rica," in "5 Mysterious Monuments from Around the World"
Tristin Hopper, HowStuffWorks, a Discovery Company

"While clearing the Costa Rican jungle for banana plantations in 1940, employees of the United Fruit Company began uncovering large stone spheres buried in the forest floor.

"Almost immediately, the mysterious spheres became prized lawn ornaments, ending up on the front yards of government buildings and fruit company executives throughout Costa Rica. Many spheres were broken in transit, and others were purposely dynamited by treasure hunters.

"It was a sorry fate for one of the region's greatest archaeological treasures. Hundreds of spheres, ranging in size from a basketball to a compact car, have been unearthed in the last 70 years. Carved by the ancestors of Costa Rica's indigenous people, the near-perfect spheres would have needed to be shaped using only other stones, since they didn't have access to metal tools. Sphere-carving was much more than a passing fad: Archaeologists estimate that native Costa Ricans were carving spheres from as early as 600 AD to as late as 1500 AD [source: Hoopes].

"Archaeologists remain stumped over the purpose of the spheres. The people who made them had no written records, and their culture was decimated soon after the Spanish conquest. Much like the Easter Island moai, one theory assumes that the spheres were simply status symbols. The stones also might have once been arranged into massive patterns that had astronomical significance. Since almost every sphere has been moved from its original location, however, researchers are sceptical that the true meaning of the spheres will ever be discovered."

The archaeologists will likely remain stumped, unless they decide to bring in a geologist. Someone whose job involves studying things that people made might reasonably assume that a piece of rock that's spherical was made by people.

It's sort of like 'if you've got a hammer, everything looks like a nail.'

The Lemming doesn't doubt that the Costa Rican stone spheres were moved by people. Those particular ones may even have been made by people. Knowledge of why they were moved may never be known.

The stones themselves, though: Stumped archeologists might want to compare notes with geologists.

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"Stone spheres"
Strange Earth, The Edinburgh Geologist - Issue no 24 ( Spring 1990)

"Until recently, the stone spheres of Central America were regarded as the mysterious vestiges of an unknown culture. Ranging in diameter from less than 1 inch to over 11 feet and almost perfectly spherical, their mode of construction was an enigma. The precision with which these spheres had been shaped was incredible. A sphere from Costa Rica, 7.03 feet in diameter with an estimated weight of 16 tons, for example, was measured as being within one quarter of an inch of a perfect sphere.

"Apart from those found in Costa Rica, precisely rounded stone spheres were also known from Honduras, Belize and Mexico. It was not until 1967 however, when Matthew Stirling and his colleagues saw hundreds of spheres littering the ground at Agua Blanca, near Guadalajara, in Mexico, did they suspect that the origin of the spheres was a geological rather than archaeological problem. Stirling's report to the National Geographic Committee for Research and Exploration resulted in a joint National Geographic - Smithsonian Institution - United States Geological Survey expedition to the Agua Blanca area in 1968...."

The geological explanation isn't quite so mysterious: but it answers the 'how were these things made' question without introducing all that many more mysteries. Which satisfies Occam's Razor. Which is another topic.