Middle Pleistocene

The geological interval from about 774,000 to 129,000 years ago, marked by repeated glacial cycles and major changes in human evolution.

Marine isotope stages: A sequence of climate intervals inferred chiefly from oxygen-isotope variations in marine sediments. They provide the standard numbered framework for tracking the interval’s alternating cold and warm phases.
Chibanian: The formal name of the Middle Pleistocene geological age, spanning approximately 774,000 to 129,000 years ago. It is the formally ratified age corresponding to the interval’s dates.
Homo heidelbergensis: An extinct human species or species complex known from Middle Pleistocene fossils in Africa and Europe. The name is commonly applied to fossils central to debates about human ancestry in this interval.
Pleistocene glaciation: Repeated expansions and contractions of continental ice sheets during the Pleistocene Epoch. The Middle Pleistocene forms a major part of this broader pattern of glaciation.
Milankovitch cycles: Long-term variations in Earth’s orbit and axial orientation that alter the distribution of incoming sunlight. Their changing sunlight patterns paced glacial cycles during the Middle Pleistocene.
Chiba Section: A geological sequence in Japan whose deposits record climate changes around the Middle–Late Pleistocene boundary. Its boundary strata anchor the formal base of the Chibanian.
Neanderthals: An extinct human group that lived mainly in Europe and western Asia, evolving during the Middle Pleistocene. Their lineage emerged from populations whose fossils appear during this interval.
Sea-level rise: An increase in the average height of the ocean surface relative to land. Ice-sheet melting during warm phases raised sea levels and altered coastlines.
Mid-Pleistocene Transition: A long-term shift, roughly 1.2 to 0.7 million years ago, toward longer and stronger glacial cycles. This transition established the distinctive, roughly 100,000-year cycles characteristic of much of the interval.
Jaramillo Subchron: A brief interval of reversed geomagnetic polarity within the Matuyama Chron, about one million years ago. Its magnetic signature helps correlate and date older deposits near the interval’s beginning.

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