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The Pleistocene Era is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before the Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology.
The Last Glacial Maximum (LGM), also referred to as the Last Glacial Coldest Period,[1] was the most recent time during the Last Glacial Period that ice sheets were at their greatest extent 26,000 and 20,000 years ago.[2] Ice sheets covered much of Northern North America, Northern Europe, and Asia and profoundly affected Earth's climate by causing a major expansion of deserts,[3] along with a large drop in sea levels.[4]
Based on changes in position of ice sheet margins dated via terrestrial cosmogenic nuclides and radiocarbon dating, growth of ice sheets in the southern hemisphere commenced 33,000 years ago and maximum coverage has been estimated to have occurred sometime between 26,500 years ago[1] and 20,000 years ago.[5] After this, deglaciation caused an abrupt rise in sea level. Decline of the West Antarctica ice sheet occurred between 14,000 and 15,000 years ago, consistent with evidence for another abrupt rise in the sea level about 14,500 years ago.[6][7] Glacier fluctuations around the Strait of Magellan suggest the peak in glacial surface area was constrained to between 25,200 and 23,100 years ago.[8]
There are no agreed dates for the beginning and end of the LGM, and researchers select dates depending on their criteria and the data set consulted. Jennifer French, an archeologist specialising in the European Palaeolithic, dates its onset at 27,500 years ago, with ice sheets at their maximum by around 26,000 years ago and deglaciation commencing between 20,000 and 19,000 years ago.[9] The LGM is referred to in Britain as the Dimlington Stadial, dated to between 31,000 and 16,000 years ago.[10][11]
The Younger Dryas, which occurred circa 12,900 to 11,700 years BP,[2] was a return to glacial conditions which temporarily reversed the gradual climatic warming after the Last Glacial Maximum,[3] which lasted from circa 27,000 to 20,000 years BP. The Younger Dryas was the last stage of the Pleistocene epoch that spanned from 2,580,000 to 11,700 years BP and it preceded the current, warmer Holocene epoch. The Younger Dryas was the most severe and longest lasting of several interruptions to the warming of the Earth's climate, and it was preceded by the Late Glacial Interstadial (also called the Bølling–Allerød interstadial), an interval of relative warmth that lasted from 14,670 to 12,900 BP.
The change was relatively sudden, took place over decades, and resulted in a decline of temperatures in Greenland by 4~10 °C (7.2~18 °F),[4] and advances of glaciers and drier conditions over much of the temperate Northern Hemisphere. A number of theories have been put forward about the cause, and the hypothesis historically most supported by scientists is that the Atlantic meridional overturning circulation, which transports warm water from the Equator towards the North Pole, was interrupted by an influx of fresh, cold water from North America into the Atlantic.[5] However, several issues do exist with this hypothesis, one of which is the lack of a clear geomorphological route for the meltwater. In fact, the originator of the metwater hypothesis, Wallace Broecker, stated in 2010 that "The long-held scenario that the Younger Dryas was a one-time outlier triggered by a flood of water stored in proglacial Lake Agassiz has fallen from favor due to lack of a clear geomorphic signature at the correct time and place on the landscape".[6] A volcanic trigger has been proposed more recently,[7] and the presence of anomalously high levels of volcanism immediately preceding the onset of the Younger Dryas has been confirmed in both ice cores[8] and cave deposits.[9]
The Younger Dryas did not affect the climate equally worldwide, but the average worldwide temperature changed drastically. For example, in the Southern Hemisphere and some areas of the Northern Hemisphere, such as southeastern North America, a slight warming occurred.[10]
The Younger Dryas is named after an indicator genus, the alpine-tundra wildflower Dryas octopetala, as its leaves are occasionally abundant in late glacial, often minerogenic-rich sediments, such as the lake sediments of Scandinavia.
The Holocene (/ˈhɒl.əsiːn, -oʊ-, ˈhoʊ.lə-, -loʊ-/)[2][3] is the current geological epoch. It began approximately 9,700 years before the Common Era (BCE)[a] (11,650 cal years BP, or 300 HE). It follows the Last Glacial Period, which concluded with the Holocene glacial retreat.[4] The Holocene and the preceding Pleistocene[5] together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1. It is considered by some to be an interglacial period within the Pleistocene Epoch, called the Flandrian interglacial.[6]
The Holocene corresponds with the rapid proliferation, growth, and impacts of the human species worldwide, including all of its written history, technological revolutions, development of major civilizations, and overall significant transition towards urban living in the present. The human impact on modern-era Earth and its ecosystems may be considered of global significance for the future evolution of living species, including approximately synchronous lithospheric evidence, or more recently hydrospheric and atmospheric evidence of the human impact. In July 2018, the International Union of Geological Sciences split the Holocene Epoch into three distinct ages based on the climate, Greenlandian (11,700 years ago to 8,200 years ago), Northgrippian (8,200 years ago to 4,200 years ago) and Meghalayan (4,200 years ago to the present), as proposed by International Commission on Stratigraphy.[7] The oldest age, the Greenlandian was characterized by a warming following the preceding ice age. The Northgrippian Age is known for vast cooling due to a disruption in ocean circulations that was caused by the melting of glaciers. The most recent age of the Holocene is the present Meghalayan, which began with extreme drought that lasted around 200 years.[7]
This video covers major events that occurred in the Holocene (our current epoch). Major glacial and interglacial cycles occurred in the Pleistocene and after the LGM, climate shifted back into a cooling regime called the Younger Dryas. The possible causes of the Younger Dryas include obstruction of ocean circulation and comet impacts. The impact hypothesis has also been proposed as a possible cause of the megafauna extinctions that occurred around this time. Large mammals, such as mammoths, mastodons, saber tooth cats, American elephants, giant armadillos, giant ground sloths, and short faced bears went extinct during this extinction event. Why? 2 hypotheses: the human-hunting hypothesis (humans hunted these animals to extinction) and the climate hypothesis (the rapid switch to cooling and possible comet impacts & wildfires caused the extinctions). After the Younger Dryas, things warmed back up and temperature remained relatively constant until ~1950 when the Anthropocene began. The Anthropocene and current climate change is discussed in the video: The Anthropocene Epoch.
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The Last Glacial Maximum (LGM), colloquially called the last ice age, was a period in Earth’s history that occurred roughly 26,000 to 19,000 years ago.
- A “lost continent” called Sundaland, a southeastern extension of Asia which forms the island regions of Indonesia today. Some scholars see a connection with this location and the mythical site of Atlantis, though there are many other theories.
- The Bering land bridge, now a strait, connecting Asia and North America. It is central to the theory explaining how ancient humans crossed between the two continents.
- Another land bridge connected the island of Great Britain with the rest of continental Europe. The island of Ireland is in turn connected to Great Britain by a giant ice sheet.
- In Japan, the low water level made the Sea of Japan a lake, and a land bridge connected the region to the Asian mainland. The Yellow Sea—famous as a modern-day fishing location—was completely dry.
- The cold temperatures also caused the polar parts of continents to be covered by massive ice sheets, with glaciers forming in mountainous areas.
- Most of Canada and Northern Europe was covered with large ice sheets. The U.S. was a mix of ice sheets, alpine deserts, snow forests, semi-arid scrubland and temperate grasslands. Areas that are deserts today—like the Mojave—were filled with lakes. The Great Salt Lake in Utah is a remnant from this time.
- Africa had a mix of grasslands in its southern half and deserts in the north—the Sahara Desert existed then as well...
- and Asia was a mix of tropical deserts in the west, alpine deserts in China, and grasslands in the Indian subcontinent.
- Several large animals like the woolly mammoth, the mastodon, the giant beaver, and the saber-toothed tiger roamed the world in extremely harsh conditions, but sadly all are extinct today.
- However, not all megafauna from the LGM disappeared forever; many species are still alive, including the Bactrian camel, the tapir, the musk ox, and the white rhinoceros—though the latter is now an endangered species.
| Pleistocene | |
|---|---|
 Map of the sea levels during the Last Glacial Maximum (glaciers not shown) | |
| Chronology | |
| Etymology | |
| Name formality | Formal |
| Usage information | |
| Celestial body | Earth |
| Regional usage | Global (ICS) |
| Definition | |
| Chronological unit | Epoch |
| Stratigraphic unit | Series |
| Time span formality | Formal |
| Lower boundary definition |
|
| Lower boundary GSSP | Monte San Nicola Section, Gela, Sicily, Italy 37.1469°N 14.2035°E |
| Lower GSSP ratified | 2009 (as base of Quaternary and Pleistocene)[3] |
| Upper boundary definition | End of the Younger Dryas stadial |
| Upper boundary GSSP | NGRIP2 ice core, Greenland 75.1000°N 42.3200°W |
| Upper GSSP ratified | 2008 (as base of Holocene)[4] |
| Part of a series on |
| Human history and prehistory |
|---|
| ↑ before Homo (Pliocene epoch) |
| ↓ Future (Holocene epoch) |
The Pleistocene (/ˈplaɪstəˌsiːn, -stoʊ-/ PLY-stə-seen, -stoh-;[5][6] often referred to colloquially as the Ice Age) is the geological epoch that lasted from c. 2.58 million to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek πλεῖστος (pleîstos), meaning "most", and καινός (kainós; latinized as cænus), meaning "new".
At the end of the preceding Pliocene, the previously isolated North and South American continents were joined by the Isthmus of Panama, causing a faunal interchange between the two regions and changing ocean circulation patterns, with the onset of glaciation in the Northern Hemisphere occurring around 2.7 million years ago. During the Early Pleistocene (2.58–0.8 Ma), archaic humans of the genus Homo originated in Africa and spread throughout Afro-Eurasia. The end of the Early Pleistocene is marked by the Mid-Pleistocene Transition, with the cyclicity of glacial cycles changing from 41,000-year cycles to asymmetric 100,000-year cycles, making the climate variation more extreme. The Late Pleistocene witnessed the spread of modern humans outside of Africa as well as the extinction of all other human species. Humans also spread to the Australian continent and the Americas for the first time, co-incident with the extinction of most large bodied animals in these regions.
The aridification and cooling trends of the preceding Neogene were continued in the Pleistocene. The climate was strongly variable depending on the glacial cycle, with the sea levels being up to 120 metres lower than present at peak glaciation, allowing the connection of Asia and North America via Beringia and the covering of most of northern North America by the Laurentide Ice Sheet.
Etymology
Charles Lyell introduced the term "Pleistocene" in 1839 to describe strata in Sicily that had at least 70% of their molluscan fauna still living today. This distinguished it from the older Pliocene Epoch, which Lyell had originally thought to be the youngest fossil rock layer. He constructed the name "Pleistocene" ("most new" or "newest") from the Greek πλεῖστος (pleīstos, "most") and καινός (kainós (latinized as cænus), "new");[8][9][10] this contrasts with the immediately preceding Pliocene ("newer", from πλείων (pleíōn, "more") and kainós) and the immediately subsequent Holocene ("wholly new" or "entirely new", from ὅλος (hólos, "whole") and kainós) epoch, which extends to the present time.
Dating
−10 — – −9 — – −8 — – −7 — – −6 — – −5 — – −4 — – −3 — – −2 — – −1 — – 0 — |
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The Pleistocene has been dated from 2.580 million (±0.005) to 11,650 years BP[11] with the end date expressed in radiocarbon years as 10,000 carbon-14 years BP.[12] It covers most of the latest period of repeated glaciation, up to and including the Younger Dryas cold spell. The end of the Younger Dryas has been dated to about 9640 BC (11,654 calendar years BP). The end of the Younger Dryas is the official start of the current Holocene Epoch. Although it is considered an epoch, the Holocene is not significantly different from previous interglacial intervals within the Pleistocene.[13] In the ICS timescale, the Pleistocene is divided into four stages or ages, the Gelasian, Calabrian, Chibanian (previously the unofficial "Middle Pleistocene"), and Upper Pleistocene (unofficially the "Tarantian").[14][15][note 1] In addition to these international subdivisions, various regional subdivisions are often used.
In 2009 the International Union of Geological Sciences (IUGS) confirmed a change in time period for the Pleistocene, changing the start date from 1.806 to 2.588 million years BP, and accepted the base of the Gelasian as the base of the Pleistocene, namely the base of the Monte San Nicola GSSP.[17] The start date has now been rounded down to 2.580 million years BP.[11] The IUGS has yet to approve a type section, Global Boundary Stratotype Section and Point (GSSP), for the upper Pleistocene/Holocene boundary (i.e. the upper boundary). The proposed section is the North Greenland Ice Core Project ice core 75° 06' N 42° 18' W.[18] The lower boundary of the Pleistocene Series is formally defined magnetostratigraphically as the base of the Matuyama (C2r) chronozone, isotopic stage 103. Above this point there are notable extinctions of the calcareous nannofossils: Discoaster pentaradiatus and Discoaster surculus.[19][20] The Pleistocene covers the recent period of repeated glaciations.
The name Plio-Pleistocene has, in the past, been used to mean the last ice age. Formerly, the boundary between the two epochs was drawn at the time when the foraminiferal species Hyalinea baltica first appeared in the marine section at La Castella, Calabria, Italy;[21] however, the revised definition of the Quaternary, by pushing back the start date of the Pleistocene to 2.58 Ma, results in the inclusion of all the recent repeated glaciations within the Pleistocene.
Radiocarbon dating is considered to be inaccurate beyond around 50,000 years ago. Marine isotope stages (MIS) derived from Oxygen isotopes are often used for giving approximate dates.
Deposits
Pleistocene non-marine sediments are found primarily in fluvial deposits, lakebeds, slope and loess deposits as well as in the large amounts of material moved about by glaciers. Less common are cave deposits, travertines and volcanic deposits (lavas, ashes). Pleistocene marine deposits are found primarily in shallow marine basins mostly (but with important exceptions) in areas within a few tens of kilometres of the modern shoreline. In a few geologically active areas such as the Southern California coast, Pleistocene marine deposits may be found at elevations of several hundred metres.
Paleogeography and climate
The modern continents were essentially at their present positions during the Pleistocene, the plates upon which they sit probably having moved no more than 100 km (62 mi) relative to each other since the beginning of the period. In glacial periods, the sea level would drop by up to 120 m (390 ft) lower than today[22] during peak glaciation, exposing large areas of present continental shelf as dry land.
According to Mark Lynas (through collected data), the Pleistocene's overall climate could be characterised as a continuous El Niño with trade winds in the south Pacific weakening or heading east, warm air rising near Peru, warm water spreading from the west Pacific and the Indian Ocean to the east Pacific, and other El Niño markers.[23]
Glacial features
Pleistocene climate was marked by repeated glacial cycles in which continental glaciers pushed to the 40th parallel in some places. It is estimated that, at maximum glacial extent, 30% of the Earth's surface was covered by ice. In addition, a zone of permafrost stretched southward from the edge of the glacial sheet, a few hundred kilometres in North America, and several hundred in Eurasia. The mean annual temperature at the edge of the ice was −6 °C (21 °F); at the edge of the permafrost, 0 °C (32 °F).
Each glacial advance tied up huge volumes of water in continental ice sheets 1,500 to 3,000 metres (4,900–9,800 ft) thick, resulting in temporary sea-level drops of 100 metres (300 ft) or more over the entire surface of the Earth. During interglacial times, such as at present, drowned coastlines were common, mitigated by isostatic or other emergent motion of some regions.
The effects of glaciation were global. Antarctica was ice-bound throughout the Pleistocene as well as the preceding Pliocene. The Andes were covered in the south by the Patagonian ice cap. There were glaciers in New Zealand and Tasmania. The current decaying glaciers of Mount Kenya, Mount Kilimanjaro, and the Ruwenzori Range in east and central Africa were larger. Glaciers existed in the mountains of Ethiopia and to the west in the Atlas mountains.
In the northern hemisphere, many glaciers fused into one. The Cordilleran Ice Sheet covered the North American northwest; the east was covered by the Laurentide. The Fenno-Scandian ice sheet rested on northern Europe, including much of Great Britain; the Alpine ice sheet on the Alps. Scattered domes stretched across Siberia and the Arctic shelf. The northern seas were ice-covered.
South of the ice sheets large lakes accumulated because outlets were blocked and the cooler air slowed evaporation. When the Laurentide Ice Sheet retreated, north-central North America was totally covered by Lake Agassiz. Over a hundred basins, now dry or nearly so, were overflowing in the North American west. Lake Bonneville, for example, stood where Great Salt Lake now does. In Eurasia, large lakes developed as a result of the runoff from the glaciers. Rivers were larger, had a more copious flow, and were braided. African lakes were fuller, apparently from decreased evaporation. Deserts, on the other hand, were drier and more extensive. Rainfall was lower because of the decreases in oceanic and other evaporation.
It has been estimated that during the Pleistocene, the East Antarctic Ice Sheet thinned by at least 500 meters, and that thinning since the Last Glacial Maximum is less than 50 meters and probably started after ca 14 ka.[24]
Major events
During the 2.5 million years of the Pleistocene, numerous cold phases called glacials (Quaternary ice age), or significant advances of continental ice sheets, in Europe and North America, occurred at intervals of approximately 40,000 to 100,000 years. The long glacial periods were separated by more temperate and shorter interglacials which lasted about 10,000–15,000 years. The last cold episode of the last glacial period ended about 10,000 years ago.[25] Over 11 major glacial events have been identified, as well as many minor glacial events.[26] A major glacial event is a general glacial excursion, termed a "glacial." Glacials are separated by "interglacials". During a glacial, the glacier experiences minor advances and retreats. The minor excursion is a "stadial"; times between stadials are "interstadials".
These events are defined differently in different regions of the glacial range, which have their own glacial history depending on latitude, terrain and climate. There is a general correspondence between glacials in different regions. Investigators often interchange the names if the glacial geology of a region is in the process of being defined. However, it is generally incorrect to apply the name of a glacial in one region to another.
For most of the 20th century only a few regions had been studied and the names were relatively few. Today the geologists of different nations are taking more of an interest in Pleistocene glaciology. As a consequence, the number of names is expanding rapidly and will continue to expand. Many of the advances and stadials remain unnamed. Also, the terrestrial evidence for some of them has been erased or obscured by larger ones, but evidence remains from the study of cyclical climate changes.
The glacials in the following tables show historical usages, are a simplification of a much more complex cycle of variation in climate and terrain, and are generally no longer used. These names have been abandoned in favour of numeric data because many of the correlations were found to be either inexact or incorrect and more than four major glacials have been recognised since the historical terminology was established.[26][27][28]
| Region | Glacial 1 | Glacial 2 | Glacial 3 | Glacial 4 |
|---|---|---|---|---|
| Alps | Günz | Mindel | Riss | Würm |
| North Europe | Eburonian | Elsterian | Saalian | Weichselian |
| British Isles | Beestonian | Anglian | Wolstonian | Devensian |
| Midwest U.S. | Nebraskan | Kansan | Illinoian | Wisconsinan |
| Region | Interglacial 1 | Interglacial 2 | Interglacial 3 |
|---|---|---|---|
| Alps | Günz-Mindel | Mindel-Riss | Riss-Würm |
| North Europe | Waalian | Holsteinian | Eemian |
| British Isles | Cromerian | Hoxnian | Ipswichian |
| Midwest U.S. | Aftonian | Yarmouthian | Sangamonian |
Corresponding to the terms glacial and interglacial, the terms pluvial and interpluvial are in use (Latin: pluvia, rain). A pluvial is a warmer period of increased rainfall; an interpluvial, of decreased rainfall. Formerly a pluvial was thought to correspond to a glacial in regions not iced, and in some cases it does. Rainfall is cyclical also. Pluvials and interpluvials are widespread.
There is no systematic correspondence of pluvials to glacials, however. Moreover, regional pluvials do not correspond to each other globally. For example, some have used the term "Riss pluvial" in Egyptian contexts. Any coincidence is an accident of regional factors. Only a few of the names for pluvials in restricted regions have been stratigraphically defined.
Palaeocycles
The sum of transient factors acting at the Earth's surface is cyclical: climate, ocean currents and other movements, wind currents, temperature, etc. The waveform response comes from the underlying cyclical motions of the planet, which eventually drag all the transients into harmony with them. The repeated glaciations of the Pleistocene were caused by the same factors.
The Mid-Pleistocene Transition, approximately one million years ago, saw a change from low-amplitude glacial cycles with a dominant periodicity of 41,000 years to asymmetric high-amplitude cycles dominated by a periodicity of 100,000 years.[29]
However, a 2020 study concluded that ice age terminations might have been influenced by obliquity since the Mid-Pleistocene Transition, which caused stronger summers in the Northern Hemisphere.[30]
Milankovitch cycles
Glaciation in the Pleistocene was a series of glacials and interglacials, stadials and interstadials, mirroring periodic changes in climate. The main factor at work in climate cycling is now believed to be Milankovitch cycles. These are periodic variations in regional and planetary solar radiation reaching the Earth caused by several repeating changes in the Earth's motion. The effects of Milankovitch cycles were enhanced by various positive feedbacks related to increases in atmospheric carbon dioxide concentrations and Earth's albedo.[31]
Milankovitch cycles cannot be the sole factor responsible for the variations in climate since they explain neither the long term cooling trend over the Plio-Pleistocene, nor the millennial variations in the Greenland Ice Cores known as Dansgaard-Oeschger events and Heinrich events. Milankovitch pacing seems to best explain glaciation events with periodicity of 100,000, 40,000, and 20,000 years. Such a pattern seems to fit the information on climate change found in oxygen isotope cores.
Oxygen isotope ratio cycles
In oxygen isotope ratio analysis, variations in the ratio of 18
O to 16
O (two isotopes of oxygen) by mass (measured by a mass spectrometer) present in the calcite of oceanic core samples is used as a diagnostic of ancient ocean temperature change and therefore of climate change. Cold oceans are richer in 18
O, which is included in the tests of the microorganisms (foraminifera) contributing the calcite.
A more recent version of the sampling process makes use of modern glacial ice cores. Although less rich in 18
O than sea water, the snow that fell on the glacier year by year nevertheless contained 18
O and 16
O in a ratio that depended on the mean annual temperature.
Temperature and climate change are cyclical when plotted on a graph of temperature versus time. Temperature coordinates are given in the form of a deviation from today's annual mean temperature, taken as zero. This sort of graph is based on another of isotope ratio versus time. Ratios are converted to a percentage difference from the ratio found in standard mean ocean water (SMOW).
The graph in either form appears as a waveform with overtones. One half of a period is a Marine isotopic stage (MIS). It indicates a glacial (below zero) or an interglacial (above zero). Overtones are stadials or interstadials.
According to this evidence, Earth experienced 102 MIS stages beginning at about 2.588 Ma BP in the Early Pleistocene Gelasian. Early Pleistocene stages were shallow and frequent. The latest were the most intense and most widely spaced.
By convention, stages are numbered from the Holocene, which is MIS1. Glacials receive an even number; interglacials, odd. The first major glacial was MIS2-4 at about 85–11 ka BP. The largest glacials were 2, 6, 12, and 16; the warmest interglacials, 1, 5, 9 and 11. For matching of MIS numbers to named stages, see under the articles for those names.
Fauna
Both marine and continental faunas were essentially modern but with many more large land mammals such as Mammoths, Mastodons, Diprotodon, Smilodon, tiger, lion, Aurochs, short-faced bears, giant sloths, Gigantopithecus and others. Isolated landmasses such as Australia, Madagascar, New Zealand and islands in the Pacific saw the evolution of large birds and even reptiles such as the Elephant bird, moa, Haast's eagle, Quinkana, Megalania and Meiolania.
The severe climatic changes during the Ice Age had major impacts on the fauna and flora. With each advance of the ice, large areas of the continents became totally depopulated, and plants and animals retreating southwards in front of the advancing glacier faced tremendous stress. The most severe stress resulted from drastic climatic changes, reduced living space, and curtailed food supply. A major extinction event of large mammals (megafauna), which included mammoths, mastodons, saber-toothed cats, glyptodons, the woolly rhinoceros, various giraffids, such as the Sivatherium; ground sloths, Irish elk, cave lions, cave bears, Gomphotheres, American lions, dire wolves, and short-faced bears, began late in the Pleistocene and continued into the Holocene. Neanderthals also became extinct during this period. At the end of the last ice age, cold-blooded animals, smaller mammals like wood mice, migratory birds, and swifter animals like whitetail deer had replaced the megafauna and migrated north. Late Pleistocene bighorn sheep were more slender and had longer legs than their descendants today. Scientists believe that the change in predator fauna after the late Pleistocene extinctions resulted in a change of body shape as the species adapted for increased power rather than speed.[32]
The extinctions hardly affected Africa but were especially severe in North America where native horses and camels were wiped out.
- Asian land mammal ages (ALMA) include Zhoukoudianian, Nihewanian, and Yushean.
- European land mammal ages (ELMA) include the Villafranchian, Galerian, and Aurelian
- North American land mammal ages (NALMA) include Blancan (4.75–1.8), Irvingtonian (1.8–0.24) and Rancholabrean (0.24–0.01) in millions of years. The Blancan extends significantly back into the Pliocene.
- South American land mammal ages (SALMA) include Uquian (2.5–1.5), Ensenadan (1.5–0.3) and Lujanian (0.3–0.01) in millions of years. The Uquian previously extended significantly back into the Pliocene, although the new definition places it entirely within the Pleistocene.
In July 2018, a team of Russian scientists in collaboration with Princeton University announced that they had brought two female nematodes frozen in permafrost, from around 42,000 years ago, back to life. The two nematodes, at the time, were the oldest confirmed living animals on the planet.[33][34]
Humans
The evolution of anatomically modern humans took place during the Pleistocene.[35][36] In the beginning of the Pleistocene Paranthropus species were still present, as well as early human ancestors, but during the lower Palaeolithic they disappeared, and the only hominin species found in fossilic records is Homo erectus for much of the Pleistocene. Acheulean lithics appear along with Homo erectus, some 1.8 million years ago, replacing the more primitive Oldowan industry used by A. garhi and by the earliest species of Homo. The Middle Paleolithic saw more varied speciation within Homo, including the appearance of Homo sapiens about 300,000 years ago.[37]
According to mitochondrial timing techniques, modern humans migrated from Africa after the Riss glaciation in the Middle Palaeolithic during the Eemian Stage, spreading all over the ice-free world during the late Pleistocene.[38][39][40] A 2005 study posits that humans in this migration interbred with archaic human forms already outside of Africa by the late Pleistocene, incorporating archaic human genetic material into the modern human gene pool.[41]
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See also[edit]
Explanatory notes
References
- ^ Cohen, K. M.; Finney, S. C.; Gibbard, P. L.; Fan, J.-X. (January 2020). "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. Retrieved 23 February 2020.
- ^ Mike Walker; et al. (December 2018). "Formal ratification of the subdivision of the Holocene Series/Epoch (Quaternary System/Period)" (PDF). Episodes. Subcommission on Quaternary Stratigraphy (SQS). 41 (4): 213–223. doi:10.18814/epiiugs/2018/018016. Retrieved 11 November 2019.
- ^ Gibbard, Philip; Head, Martin (September 2010). "The newly-ratified definition of the Quaternary System/Period and redefinition of the Pleistocene Series/Epoch, and comparison of proposals advanced prior to formal ratification" (PDF). Episodes. 33 (3): 152–158. doi:10.18814/epiiugs/2010/v33i3/002. Retrieved 8 December 2020.
- ^ Walker, Mike; Johnse, Sigfus; Rasmussen, Sune; Steffensen, Jørgen-Peder; Popp, Trevor; Gibbard, Phillip; et al. (June 2008). "The Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) in the NGRIP ice core". Episodes. 31 (2): 264–267. doi:10.18814/epiiugs/2008/v31i2/016.
- ^ Jones, Daniel (2003) [1917]. "Pleistocene". In Peter Roach; James Hartman; Jane Setter (eds.). English Pronouncing Dictionary. Cambridge: Cambridge University Press. ISBN 3-12-539683-2.
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External links
- Late Pleistocene environments of the southern high plains, 1975, edited by Wendorf and Hester.
- Pleistocene Microfossils: 50+ images of Foraminifera
- Stepanchuk V.N., Sapozhnykov I.V. Nature and man in the pleistocene of Ukraine. 2010
- Human Timeline (Interactive) – Smithsonian, National Museum of Natural History (August 2016).
- Pleistocene Park: Conservation Project to Restore a Pleistocene Ecology and Protect Permafrost Soils in Northern Siberia
