A 3,700-year-old clay tablet has revealed that the ancient Babylonians understood the Pythagorean theorem more than 1,000 years before the birth of the Greek philosopher Pythagoras, who is widely associated with the idea. The tablet, known as Si.427, was used by ancient land surveyors to draw accurate boundaries and is engraved with cuneiform markings which form a mathematical table instructing the reader on how to make accurate right triangles. The tablet is the earliest known example of applied geometry.

A French archeological expedition first excavated the tablet, which dates to between 1900 and 1600 B.C in what is now Iraq in 1894, and it is currently housed in the Istanbul Archeological Museum. But it is only just now that researchers have discovered the significance of its ancient markings.

"It is generally accepted that trigonometry — the branch of maths that is concerned with the study of triangles — was developed by the ancient Greeks studying the night sky," in the second century B.C., Daniel Mansfield, a mathematician at the University of New South Wales in Australia and the discoverer of the tablet's meaning, said in a statement. "But the Babylonians developed their own alternative 'proto-trigonometry' to solve problems related to measuring the ground, not the sky."

According to Mansfield, Si.427 is the Old Babylonian period's only known example of a cadastral document, or a plan surveyors used to define land boundaries. "In this case, it tells us legal and geometric details about a field that's split after some of it was sold off," Mansfield said.

The tablet details a marshy field with various structures, including a tower, built upon it. The tablet is engraved with three sets of Pythagorean triples: three whole numbers for which the sum of the squares of the first two equals the square of the third. The triples engraved on Si.427 are 3, 4, 5; 8, 15, 17; and 5, 12, 13. These were likely used to help determine the land's boundaries.