The Eemian is the the most recent interglacial period, enduring from the end of the penultimate glaciation about 130 thousand years ago (kya) until approximately 107 kya when the most recent Ice age commenced. The Eemian is generally viewed as a typical interglacial event, with characteristics including relatively high sea level, retreat to minimum size of global ice sheets, and the establishment of biotic assemblages that closely parallel those at present. According to the bulk of available proxy data, the Eemian was slightly warmer everywhere than the current late Holocene period.
The climate of the Eemian has strong resemblance to the present Holocene period; both epochs were interglacials of relatively short duration, initiated by natural cycles of global warming. After initial glacial melting, the Earth's albedo changed to absorb more sunlight and thus intensify the warming trend in a positive feedback loop of the natural warming trend. The U.S. National Research Council classifies both the Holocene and Eemian epochs as examples of Abrupt Climate Change. The temperature maximum of the Eemian appears to have occurred about 127 to 125 kya, based upon coral reef formation details and terrestrial pollen core records.
Variations of temperature, methane, and atmospheric carbon dioxide concentrations derived from air trapped within ice cores from Antarctica (adapted from Sowers and Bender, 1995; Blunier et al., 1997; Fischer et al., 1999; Petit et al., 1999).25 years. Source: IPCC, Technical Summary of the Working Group I Report, 2001
Geology and Sea Level
Sea levels were roughly five to seven meters higher at the peak of Eemian warmth, compared to current sea heights. The chief remnant of the Eemian geology are exposed coral reefs in disparate locations around the globe, which reefs were formed during the Eemian. There are also numerous lacustrine and other sedimentary deposits identified with the copious deposition regime of the Eemian's torrential rivers carrying glacial melt from higher elevations.
Sketch of the extinct Straight-tusked elephant (Elephas antiquus)
As with other aspects of Eemian research, the ecological record is strongest in Europe, because of the interest in understanding the relationship between Neanderthals and modern humans. The warming period in Europe brought denser forests, the northern of which were rich with genus Tilia, Taxus and Corylus species. There is also evidence that disturbance regimes created some clearings that were hospitable to Neanderthal hunting.
Pollen cores from the Lake Grobern basin are some of the most descriptive of forest succession in the Eemian. Initial phases at the outset of the Eemian were dominated by Birch (Betula) and Juniper (Juniperus) species; within half a millennium Pine (Pinus) species created inroads to produce Pine-Birch forests, and less than a millennium later Oak (quercus) species had intruded to form Pine-Oak dominant forests. Along with Oak, entered species of Elm (Ulmus), Hazel (Corylus) and Ash (Fraxinus), with admixtures of these four new genera supplanting Pine over the next one thousand years.
Near the peak of Eemian forest density at Lake Grobern, species of genera Lime (Tilia) and Yew (Taxus) entered the forest mix at around 127 kya; soon thereafter followed large numbers of Hornbeam (Carpinus) trees. From the period 123 to 114 kya genus Spruce (Picea) and Fir (Abies) became established canopy species, steadily supplanting Ulmus, Fraxinus, Tilia and Taxus trees. In this presumed cooling period Pinus and Juniperus also re-appeared in significant numbers, completing the forest succession of the Eemian at Grobern.
Because their is a research bias toward European megafauna (due to the ease of detection of large carcasses and to the preoccupation with Neanderthal hunting), there is a disproportionate number of large terrestrial mammals in the European Eemian theatre. The Lehringen marl pit, for example, has yielded lake basin deposits evidencing Gray wolf (Canis lupis), Brown bear (Ursus arctos), Eurasian beaver (Castor fiber), Northern Eurasian rhinoceros (Dicerorhinus kirchbergensis) [extinct by the late Weichselian], Straight-tusked elephant (Elephas (Palaeoloxodon) [extinct by around 50 kya], Irish elk (Megaloceros giganteus) [extinct by about 5700 BC], Fallow deer (Dama dama), Red deer (Cervus elaphus), European roe deer (Capreolus capreolus), Aurochs (Bos primigenius) [extinct in Europe by 1627 AD, although a close relative known as the Chillingham cattle survive in two small herds], European ass (Equus hydruntinus) [became extinct in the Holocene]. It is notable that the single elephant recovery at Lehringen was found impaled with the famed Lehringen Yew Spear, measuring 2.4 meters in length, fashioned by Neanderthal man.
In southern Germany the Biedermannhohle is an Eemian epoch fissure cave within a travertine quarry at Stuttgart-Unterturkheim. There many similar megafauna were found as at Lehringen with notable additions of Red fox (Vulpes vulpes), European badger (Meles meles), Narrow-nose rhinoceros (Dicerorhinus hemitoechus) [extinct by the late Weichselian] and Lion (Pantera leo).
Relation to Hominids
Neanderthal skull, La Chapelle aux Saints. Source: Public Library of Science Neanderthals were known to have survived well even during the last full glacial epoch, although they could not thrive in the extreme north of Europe during peak glaciation. Evidence for this survival includes strong association of Neanderthal remains with bones of Arctic animals retrieved from archaeological sites of the mid-Paleolithic. The Eemian epoch in Europe correlates with only a limited number of extant instances of human habitation, according to the archaeological record; a notable excavation of the travertine in Taubach near Weimar has discovered Homo sapiens sapiens remains, and establishes that human migrations to northern Europe had begun at least by the late Eemian.
The Eemian increased the amount of low biological productivity forest in Europe, and hence reduced the amount of habitat most suitable to Homo neanderthalensis, i.e. high biological productivity associated with high sunlight cold climates of the glacial period. It is also known that the morphology of Neanderthals was well adapted to cold weather and to burst expenditure of energy as in sprinting or spear throwing. The warmer weather likely took a harsh toll on the Neanderthal species; this view is also supported by a paucity of archaeological recovery from the Eemian forests. Consequently the Eemian may have played a crucial role in allowing Homo sapiens sapiens to colonise Europe beginning about 100 thousand years before present (kya). In other words, without the Eemian warming, modern man may have had a more difficult time supplanting Neanderthals, had the H.neanderthalis species not been weakened by the end of the Eemian.
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