LIMA, PERU—Science News reports that Alejandro Chu of the Universidad Nacional Mayor de San Marcos and Gary Urton of Harvard University suggest that sets of colored and knotted strings discovered at Inkawasi, an Inca administrative center featuring a storage facility with large, rectangular rooms, may have been used to keep track of taxes. Chu and his team discovered the knotted textiles, called khipus, under traces of crops such as peanuts and chili peppers that had been spread evenly over a grid pattern impressed on the mud floor of each storage room. Chu and Urton argue that the Inkawasi khipus were coded for numbers equaling units of produce and a set percentage of a particular crop. “These khipus contain all the earmarks of the first known Inca taxation system,” Urton explained. For more, go to “An Overlooked Inca Wonder.”