For centuries, scientists have chronicled in exquisite detail how all kinds of species, from tiny bacteria to gigantic dinosaurs, spread across the planet and shaped its evolution. In 2016 researchers turned that focus to the human experience as well. Although textbooks often give a set explanation for how Homo sapiens populated the earth, new fossil discoveries are challenging those assumptions. Researchers are also documenting the incredible number of people who are fleeing their homelands because of violence and natural and man-made disasters. The migrations are so extensive that they are rapidly changing the makeup of nations. Investigators are also hotly debating whether we humans are transforming the earth's crust so extensively—by depositing layers of concrete, plastics, radiation and carbon—that we are ending a 12,000-year geologic epoch known as the Holocene and starting a totally new chapter called the Anthropocene.