He noticed that trees across the same region, in the same climate, develop rings in the same patterns.Douglass, with his knack for pattern-recognition, discovered that he could take younger wood with a known date, and then match its rings alongside the pattern of an older sample.In 1929, with a beam from Show Low, Arizona, Douglass was able to bridge the gap for the first time ever.Dates were assigned to Southwestern ruins with certainty.Sometimes a wood sample doesn't have enough tree rings or rings with growth patterns that match an already dated sample.
But for individual humans—and entire civilizations—it does not.If a Bigtooth Maple were cut down on Mount Lemmon in 2016 and it had 400 rings, you would know the tree started growing in 1616. What if it's been used to build a home or a ship or a bonfire?The rings could still tell how many years the tree lived, but not necessarily when. He set out on a series of expeditions across the southwest to bridge the gap between contemporary wood and wood beams from the ruins of civilizations long gone."We can look at the tree rings as a timeline and connect with people that lived in the past, and I think that gives us more of a sense of who we are, but also a sense of where we're going and perhaps ways to deal with some of the issues that we might collectively face."Radiocarbon dating has been a revolution in terms of the way stuff is dated in the past and is used by scientists all over the world," Pearson adds.