Although the theorem has been attributed to and named after Pythagoras and his community of scholars, it is believed that the concepts behind the theorem were known long before the Pythagoreans proved it. Among historians, an ongoing debate ensues about the possibilities that the ideas behind the Pythagorean Theorem were independently discovered by different groups at different times. A wide variety of theories exist, but there is substantial evidence that various civilizations used the Pythagorean Theorem, or were at least aware of the main principles of the theorem, to find the side lengths of right triangles.
In 1800 BCE, more than a thousand years before Pythagoras founded his school, a group of people living in Mesopotamia (located in present-day Iraq) already understood the relationship between the side lengths of a right triangle. These people, called Babylonians, were the first known group to demonstrate a conceptual understanding of the Pythagorean Theorem.
Plimpton 322 tablet with engravings of Pythagorean triples.
Try what the Egyptians did yourself! Cut a 12-inch piece of yarn and mark every inch by tying a knot. Next, try to construct a right triangle with this piece of yarn so that each side has an integer length, just like the Egyptians did.
Other Ancient Civilizations
It is believed that other ancient civilizations, such as China and India, also understood the Pythagorean Theorem before Pythagoras himself proved it. The debate about whether the theorem was discovered in one place at one time or in many places at different times still lingers today.