Last Interglacial

• 1. Discovery And Nomenclature

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  Pieter Harting stood in the Dutch countryside near Amersfoort during 1875 and examined boreholes that revealed a strange layer of sediment. He named this geological bed "Système Eémien" after the nearby river Eem, which flows through the region. The scientist noticed marine molluscan assemblages within these layers differed sharply from modern North Sea fauna. Many species found in these ancient beds now show distribution patterns stretching south to Portugal or into the Mediterranean. Harting's initial work established the foundation for identifying this warm period buried beneath glacial deposits. Subsequent researchers like Lorié in 1887 and Spaink in 1958 added detailed information about these molluscan groups. Van Voorthuysen described specific foraminifera from the type site while Zagwijn published palynology data in 1961. A multi-disciplinary investigation at the end of the 20th century re-investigated the original location using both old and new data. Scientists selected a parastratotype in the Amsterdam glacial basin known as the Amsterdam-Terminal borehole for further study. This team published uranium-thorium dating results showing late Last Interglacial deposits formed approximately 118,200 years ago with an error margin of 6,300 years.

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• 2. Global Climate Dynamics

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  The Earth's orbital parameters shifted during the early phase of this interglacial period creating greater seasonal temperature variations across the Northern Hemisphere. Temperatures peaked between 128,000 and 123,000 years before present before declining steadily through the latter half of the interval. Arctic regions experienced temperatures roughly two to four degrees Celsius higher than conditions recorded in 2011. Greenlandic ice cores revealed pronounced temperature swings indicating highly unstable climate patterns during this era. Forests expanded northward reaching North Cape Norway which currently exists as tundra above the Arctic Circle. Hardwood trees including hazel and oak grew as far north as Oulu Finland during the peak warmth. A cooling event similar to but not exactly mirroring the 8.2-kiloyear event occurred at Beckentin within the E5 phase of the Eemian. Soil samples from Sokli in northern Finland identified abrupt cold spells around 120,000 years ago caused by shifts in the North Atlantic Current. These cold periods lasted hundreds of years and triggered significant vegetation changes across these northern regions. Winter temperatures rose throughout Northern Europe while summer temperatures fell over the course of the Last Interglacial. Meltwater from the Dnieper and Volga rivers connected the Black Sea and Caspian Sea during an insolation maximum spanning 133,000 to 130,000 BP.

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• 3. Sea Level And Geography

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  Global mean sea surface levels reached heights approximately six to nine meters higher than current measurements during the peak of this warm period. The Greenland Ice Sheet contributed some portion to this rise while thermal expansion and melting mountain glaciers added further volume. Recent research on marine sediment cores offshore of the West Antarctic Ice Sheet suggests the sheet melted rapidly during the Last Interglacial. Ocean waters rose as fast as two point five meters per century according to those findings. Fossil coral reefs now exposed along the Caribbean coastlines and Red Sea shores contain internal erosion surfaces showing significant sea level instability. High sea levels transformed Fennoscandia into an island separated by a seaway passage between the Gulf of Finland and the White Sea. This connection created the Baltic Sea with much higher salinity than today's conditions. Jutland also formed an island while vast areas of northwestern Europe and the West Siberian Plain became inundated. Along the Central Mediterranean Spanish coast sea levels remained comparable to present-day measurements despite global rises. Exposed fossil coral reefs in the tropics often show truncation by erosion followed by new growth after sea levels rose again.

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• 4. European Fauna And Flora

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  Temperate-adapted species extended their ranges considerably northward across Europe due to the warmth of this interval. Hippopotamus populations notably reached as far north as North Yorkshire in northern England though they did not extend much further east than the Rhine River. Large extinct megafauna including straight-tusked elephants and narrow-nosed rhinoceroses inhabited these temperate landscapes alongside Merck's rhinoceros. Irish elk and aurochs roamed these regions together with still-living species like red deer fallow deer and wild boar. Predators such as lions cave hyenas brown bears and wolves hunted within these Last Interglacial ecosystems prior to global megafauna extinctions. The Mediterranean Sea was colonized during this period by now exotic marine invertebrates known collectively as the Senegalese Fauna. Species included the conch Thetystrombus latus the cone snail Conus ermineus and the sea snail Linatella caudata currently found only in tropical Atlantic waters off West Africa. These diverse animal communities existed before the wave of extinctions that occurred during the following Last Glacial Period.

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• 5. North American Megafauna

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  Mastodons and giant ground sloths migrated northwards into northern Canada and Alaska after the melting of the Laurentide Ice Sheet. American camels and bear-sized giant beavers also moved into these northern territories during the Last Interglacial. Lower latitudes of Canada hosted additional species including Columbian mammoths stag-moose and llamas. Steppe bison migrated from Alaska into the heartlands of North America at the beginning of this interglacial period. This migration gave rise to the giant long-horned bison first known from the Snowmass site in Colorado dating to around 120,000 years ago. The American lion appeared and became widespread across North America having descended from populations of the Eurasian cave lion that had previously migrated into Alaska. Cold-adapted taxa like the woolly mammoth contracted their ranges toward refugia as warmer conditions spread across the continent. These faunal movements marked the beginning of the Rancholabrean faunal age in North America.

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• 6. Human Evolutionary Context

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  Neanderthals colonized higher latitudes of Europe during this time interval after retreating due to unfavorable conditions earlier. They were absent from Britain likely because the region existed as an island during the Last Interglacial. Neanderthal groups engaged in diverse food-gathering activities including fishing and big-game hunting targeting straight-tusked elephants. Modern humans appeared outside Africa in Arabia reaching as far east as the Persian Gulf by this interval. Early modern human populations present in West Asia represented the earliest split of modern human lineages persisting to the present day. These populations are associated with mitochondrial haplogroup L0 according to genetic studies conducted on hominins from Skhul and Qafzeh sites. This period serves as a baseline reference point for nature conservation efforts given its climate similarity to current Holocene conditions.

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