History is the study of past events through written records, oral traditions, and archaeological evidence. It cannot be repeated or tested in the same way as science, but relies on reliable eyewitness accounts, logical consistency, and corroborating evidence. Genetic testing has shown that all humans are descended from one man who lived in Africa around 60,000 years ago, demonstrating our shared ancestry. Scientific studies of tree rings, ice cores, and other records have helped uncover what caused catastrophic periods in history like the Dark Ages through evidence of extreme weather and volcanic activity. Interpretations of history are also subject to change over time as new evidence comes to light, such as revising views of pre-Columbian civilizations in the Americas.