What are these knots telling us? Archeologists have long understood that the Inca, who ruled Peru until Spanish conquistadors arrived, used knotted cords to record information that other civilizations took down in writing. Decoding these arrangements of knots — known as khipus — has proved challenging. But there’s an old Spanish census document, listing about 132 taxpayers, now known to correspond to khipus that include 132 specific groups of six cords. Comparing the khipus and the census document during one spring break, Harvard undergrad Manny Medranomade a breakthrough: The number of unique colors used on the cords seemed to reflect the number of unique first names, and specific knots reflected the social status of the people involved. These observations, which Medrano made while noodling around with number patterns in a spreadsheet, point to new ways of decoding ancient mysteries. It’s archeology via Microsoft Excel.