All organisms encounter some amount of environmental change. Some changes occur over a short time, and may be cyclical, such as daily or seasonal variations in the amount of temperature, light, and precipitation. On longer time scales, hominins experienced large-scale shifts in temperature and precipitation that, in turn, caused vast changes in vegetation – shifts from grasslands and shrub lands to woodlands and forests, and also from cold to warm climates. Hominin environments were also altered by tectonics – earthquakes and uplift, such as the rise in elevation of the Tibetan Plateau, which changed rainfall patterns in northern China and altered the topography of a wide region. Tectonic activity can change the location and size of lakes and rivers. Volcanic eruptions and forest fires also altered the availability of food, water, shelter, and other resources. Unlike seasonal or daily shifts, the effects of many of these changes lasted for many years, and were unexpected to hominins and other organisms, raising the level of instability and uncertainty in their survival conditions.
Many organisms have habitat preferences, such as particular types of vegetation (grassland versus forests), or preferred temperature and precipitation ranges. When there’s a change in an animal’s preferred habitat, they can either move and track their favored habitat or adapt by genetic change to the new habitat. Otherwise, they become extinct. Another possibility, though, is for the adaptability of a population to increase – that is, the potential to adjust to new and changing environments. The ability to adjust to a variety of different habitats and environments is a characteristic of humans.
