Giant granite spheres of Costa Rica

These monolithic near-perfect spheres were discovered in the Diquis Delta, near the Pacific coast of southern Costa Rica. They have also been found around the southern cities of Palmar, Sur, Buenos Aires and Golfito and in the province of Guanacaste. Most of them have been dated between 800 and 1200 B.C.E. Their size is from an inch to 8 feet in diameter. Mostly made of a hard stone – granodiorite. Three large and aligned spheres point to Easter Island. The spheres are often grouped in geometric patterns such as triangles, rectangles or straight lines. At least 186 spheres have been decumented. How many more of them exist? No local source for the granite exists and no stone-working tools have been found in the vicinity of the spheres. These masterpieces are mirror-smooth and geometrically perfect. The maximum circumference error in a 6-foot, 7-inch diametre sphere in only 0.5 inch, or 0.2%. The outstanding stone-carving skills and mathematical knowledge were necessary for creation of such spheres. Unfinished spheres were never found. Did the Diquis culture possess such skills to produce them? As the ancient Costa Ricans had no written language, a chance to unearth any written records of just how they made the spheres is…none. Many spheres were discovered in the jungle and question remains: who and how made them and for what purpose? Who was responsible for their transport from quarries located 50 miles away?