Coca leaves first chewed 8,000 years ago, says research. By Jason Palmer Science and technology reporter, BBC News. Archaeological evidence has shown that foraging societies in Peru were already chewing coca leaves 8,000 years ago. Ruins beneath house floors in the northwestern Peru showed evidence of chewed coca and calcium-rich rocks. Such rocks would have been burned to create lime, chewed with coca to release more of its active chemicals. http://ping.fm/v2I6w