Just like Homo erectus before them, Homo sapiens dispersed and migrated in response to a rapidly changing climate. They did so during what geologists call the last glacial cycle (135,000 to 11,650 years ago), in large measure because of the changes it wrought on their home territories. Geographic barriers like mountains, deserts, and oceans; changing sea level; massive glaciers that soared kilometers in height; sea ice that stretched across the northern and southern oceans; rapidly changing temperatures; rain, snow, sleet, and drought; predators and changes in the availability of plants and animals they relied on for food – all influenced where, how, and when early people lived and migrated. This chapter and the next trace this migration throughout the world as humans searched for new places to live as an onslaught of climate crises struck their traditional territories.

Climate during the last glacial cycle

The last glacial cycle covers a geologic period between 135,000 and 11,650 years ago, when rapid changes in climate had profound impacts on the plants and animals that inhabited Earth. During this cycle, Earth experienced three major cold events, called stadials (these are Marine Isotope stage 6, 4, and 2, abbreviated MIS6, MIS4, and MIS2, respectively), and two major warm events, called interstadials (MIS5 and MIS3), as well as a number of smaller climate variations. The temperature changes associated with these events, along with the smaller temperature variations, are shown in Figure 1.3.