Age dating sediments
The amount of variability in environmental conditions was greater in the later stages of human evolution than in the earlier stages.Ten-million-year record of oxygen stable isotopes, measured in foraminifera recovered from deep-sea sediment cores, illustrates that global ocean temperature and glacial ice varied widely over the past 6 million years, the period of human evolution.
Some views assume that certain adaptations, such as upright walking or tool-making, were associated with drier habitat and the spread of grasslands, an idea often known as the savanna hypothesis.
Icons: (a) hominin origins, (b) habitual bipedality, (c) first stone toolmaking and eating meat/marrow from large animals, (d) onset of long-endurance mobility, (e) onset of rapid brain enlargement, (f) expansion of symbolic expression, innovation, and cultural diversity.
All organisms encounter some amount of environmental change.
This hypothesis calls attention to the variability observed in all environmental records and to the fact that the genus was not limited to a single type of environment.
Over the course of human evolution, human ancestors increased their ability to cope with changing habitats rather than specializing on a single type of environment.