Middle Pleistocene

The Middle Pleistocene, also known by its ICS official name of Chibanian, is an important age in the international geologic timescale. It is a time period that helps scientists understand the history of Earth. The Chibanian name was officially recognized in January 2020. This period is estimated to have occurred between 774,100 years ago and 129,000 years ago.

During the Middle Pleistocene, many important changes happened. It marks the time when early humans began using more advanced tools, moving from the Lower to the Middle Paleolithic. This was also a time when Earth's climate changed a lot, with big icy periods called glaciations.

The Chibanian comes after the Calabrian and before the Late Pleistocene. It began with a big change in Earth's magnetic field called the Brunhes–Matuyama reversal. The end of this period aligns with the end of the Penultimate Glacial Period and the start of the Last Interglacial period. Scientists use these time periods to study how our planet and its life have developed over millions of years.

Definition process

The International Union of Geological Sciences suggested changing the name of the Middle Pleistocene to the Ionian Age. But in November 2017, they chose the name Chibanian instead, based on rock layers found in Chiba Prefecture, Japan. The name Chibanian was officially approved by the IUGS in January 2020.

Climate

During the early Middle Pleistocene, the way Earth's climate changed shifted dramatically. The glacial cycles—the times when ice covered large parts of the planet—used to happen every 41,000 years. But then they began happening every 100,000 years instead. These cycles became uneven, with long cold periods broken by short warm times.

In different parts of the world, the climate felt these changes in various ways. In central Italy, it grew drier between 600,000 and 400,000 years ago. In the Levant, a region near the eastern Mediterranean, lakes shrank and turned into marshes. Along the coast of northwestern Australia, ocean currents helped create more coral reefs, including parts of the famous Great Barrier Reef.

Events

During the Middle Pleistocene, many animal species moved to new places and some went extinct. True horses moved from North America to Eurasia. In Europe, the mammoth species known as Mammuthus meridionalis went extinct and was replaced by the steppe mammoth, Mammuthus trogontherii. Elephants of the genus Palaeoloxodon, like the European straight-tusked elephant, moved from Africa into Eurasia. Around this time, large meat-eating mammals such as the giant hyena Pachycrocuta also went extinct in Europe.

Later in the Middle Pleistocene, the woolly mammoth, Mammuthus primigenius, appeared and replaced the steppe mammoth in Europe by about 200,000 years ago. The steppe bison, ancestor of today’s American bison, crossed the Bering land bridge into North America around 195,000 to 135,000 years ago. Also, around 500,000 years ago, a type of European aquatic frog called Palaeobatrachus went extinct.

Palaeoanthropology

The Chibanian period marks an important time for early humans. During this time, the first members of our species, Homo sapiens sapiens, began to appear between 300,000 and 400,000 years ago. Scientists found the oldest known human DNA from this era, dating back about 430,000 years.

Researchers also discovered evidence that early humans hunted beavers around 400,000 years ago. By studying animal bones found in Germany, they learned that these early people may have hunted beavers for their meat and skin. This shows how our ancestors lived and interacted with animals during the Middle Pleistocene.

Chronology

Further information: Timeline of glaciation

Further information: Marine isotope stages and Last Glacial Period

Further information: Brunhes–Matuyama reversal

The Middle Pleistocene, also called the Chibanian, is a time period in Earth's history. It started about 774,100 years ago and ended about 129,000 years ago. This period includes important changes in Earth's climate, such as ice ages, which affected the world long before humans were around in large numbers.