“This evidence supports the idea that human impact on the environment was widespread even before the industrial revolution,” said Paolo Gabrielli, a research scientist at the Byrd Polar and Climate Research Center at Ohio State and corresponding author of the study.

How exactly was it "wide spread" when there was limited technology only known to certain population groups that would have caused this type of pollution though. I can't imagine pollution being even close to as wide spread as during or after the industrial revolution as most countries and now corporate entities continue to pollute for personal and monetary gain.