We have a natural fascination with time – how landscapes have been carved over millennia, how our bodies grow and sag with age, how the stars traverse the sky each night. Scientists probe the layers beneath our feet to understand the secrets of our past. Geologists and palaeontologists sample ice, rock and fossils to reconstruct past climates and species and archaeologists pick through ancient “dustbins” (middens) in excavation sites to reimagine our historical dinner time.
Similarly, most living things produce records of their own existence in layered body tissues – often in the form of daily or yearly growth bands. The most familiar of these so-called biochronologies are tree rings, which form every year in response to seasonal cycles in temperature and rainfall.
Dendrochronology – the art of tree-ring counting – allows us to precisely date trees. Based on the rings in its trunk, a bristlecone pine in eastern California known as Methuselah is said to be the world’s oldest living thing at 4,856 years old.
