The Pliocene Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP. It is the youngest epoch of the Neogene Period in the Cenozoic Era; the Pliocene is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations within the Pleistocene, the Pliocene included the Gelasian stage, which lasted from 2.588 to 1.806 million years ago, is now included in the Pleistocene. As with other older geologic periods, the geological strata that define the start and end are well identified but the exact dates of the start and end of the epoch are uncertain; the boundaries defining the Pliocene are not set at an identified worldwide event but rather at regional boundaries between the warmer Miocene and the cooler Pliocene. The upper boundary was set at the start of the Pleistocene glaciations. Charles Lyell gave the Pliocene its name in Principles of Geology; the word pliocene comes from the Greek words πλεῖον and καινός and means "continuation of the recent", referring to the modern marine mollusc fauna.
H. W. Fowler called the term Pliocene a "regrettable barbarism" and an indication that "a good classical scholar" such as Lyell should have requested a philologist's help when coining words. To summarize the usage of these "regrettable barbarisms" in the labelling of the Cenozoic era: with the understanding that these are all new relative to the Mesozoic and Paleozoic eras. In the official timescale of the ICS, the Pliocene is subdivided into two stages. From youngest to oldest they are: Piacenzian Zanclean The Piacenzian is sometimes referred to as the Late Pliocene, whereas the Zanclean is referred to as the Early Pliocene. In the system of North American Land Mammal Ages include Hemphillian, Blancan; the Blancan extends forward into the Pleistocene. South American Land Mammal Ages include Montehermosan and Uquian. In the Paratethys area the Pliocene contains the Romanian stages; as usual in stratigraphy, there are many other local subdivisions in use. In Britain the Pliocene is divided into the following stages: Gedgravian, Pre-Ludhamian, Thurnian, Bramertonian or Antian, Pre-Pastonian or Baventian and Beestonian.
In the Netherlands the Pliocene is divided into these stages: Brunssumian C, Reuverian A, Reuverian B, Reuverian C, Tiglian A, Tiglian B, Tiglian C1-4b, Tiglian C4c, Tiglian C5, Tiglian C6 and Eburonian. The exact correlations between these local stages and the ICS stages is still a matter of detail; the global average temperature in the mid-Pliocene was 2–3 °C higher than today, carbon dioxide levels were the same as today, global sea level was 25 m higher. The northern hemisphere ice sheet was ephemeral before the onset of extensive glaciation over Greenland that occurred in the late Pliocene around 3 Ma; the formation of an Arctic ice cap is signaled by an abrupt shift in oxygen isotope ratios and ice-rafted cobbles in the North Atlantic and North Pacific ocean beds. Mid-latitude glaciation was underway before the end of the epoch; the global cooling that occurred during the Pliocene may have spurred on the disappearance of forests and the spread of grasslands and savannas. Continents continued to drift, moving from positions as far as 250 km from their present locations to positions only 70 km from their current locations.
South America became linked to North America through the Isthmus of Panama during the Pliocene, making possible the Great American Interchange and bringing a nearly complete end to South America's distinctive large marsupial predator and native ungulate faunas. The formation of the Isthmus had major consequences on global temperatures, since warm equatorial ocean currents were cut off and an Atlantic cooling cycle began, with cold Arctic and Antarctic waters dropping temperatures in the now-isolated Atlantic Ocean. Africa's collision with Europe formed the Mediterranean Sea, cutting off the remnants of the Tethys Ocean; the border between the Miocene and the Pliocene is the time of the Messinian salinity crisis. Sea level changes exposed the land bridge between Asia. Pliocene marine rocks are well exposed in the Mediterranean and China. Elsewhere, they are exposed near shores. During the Pliocene parts of southern Norway and southern Sweden, near sea level rose. In Norway this rise elevated the Hardangervidda plateau to 1200 m in the Early Pliocene.
In Southern Sweden similar movements elevated the South Swedish highlands leading to a deflection of the ancient Eridanos river from its original path across south-central Sweden into a course south of Sweden. The change to a cooler, seasonal climate had considerable impacts on Pliocene vegetation, reducing tropical species worldwide. Deciduous forests proliferated, coniferous forests and tundra covered much of the north, grasslands spread on all continents. Tropical forests were limited to a tight band around the equator, in addition to dry savannahs, deserts appeared in Asia and Africa. Both marine and co
Neanderthals are an extinct species or subspecies of archaic humans in the genus Homo, who lived within Eurasia from circa 400,000 until 40,000 years ago. The earliest fossils of Neanderthals in Europe are dated between 450,000 and 430,000 years ago, thereafter Neanderthals expanded into Southwest and Central Asia, they are known from numerous fossils, as well as stone tool assemblages. All assemblages younger than 160,000 years are of the so-called Mousterian techno-complex, characterised by tools made out of stone flakes; the type specimen is Neanderthal 1, found in Neander Valley in the German Rhineland, in 1856. Compared to modern humans, Neanderthals were stockier, with bigger bodies. In conformance with Bergmann's rule, as well as Allen's rule, this was was an adaptation to preserve heat in cold climates. Male and female Neanderthals had cranial capacities averaging 1,600 cm3 and 1,300 cm3 within the range of the values for anatomically modern humans. Average males stood around females 152 to 156 cm tall.
There has been growing evidence for admixture between Neanderthals and anatomically modern humans, reflected in the genomes of all modern non-African populations but not in the genomes of most sub-Saharan Africans. This suggests that interbreeding between Neanderthals and anatomically modern humans took place after the recent "out of Africa" migration, around 70,000 years ago. Recent admixture analyses have added to the complexity, finding that Eastern Neanderthals derived up to 2% of their ancestry from anatomically modern humans who left Africa some 100,000 years ago. Neanderthals are named after one of the first sites where their fossils were discovered in the mid-19th century in the Neander Valley, just east of Düsseldorf, at the time in the Rhine Province of the Kingdom of Prussia; the valley itself was named for Joachim Neander, Neander being the graecicized form of the surname Neumann. The German spelling of Thal "Valley" was current in the 19th century. Neanderthal 1 was known as the "Neanderthal cranium" or "Neanderthal skull" in anthropological literature, the individual reconstructed on the basis of the skull was called "the Neanderthal man".
The binomial name Homo neanderthalensis—extending the name "Neanderthal man" from the individual type specimen to the entire group—was first proposed by the Anglo-Irish geologist William King in a paper read to the British Association in 1863, although in the following year he stated that the specimen was not human and rejected the name. King's name had priority over the proposal put forward in 1866 by Homo stupidus. Popular English usage of "Neanderthal" as shorthand for "Neanderthal man", as in "the Neanderthals" or "a Neanderthal", emerged in the popular literature of the 1920s. Since the historical spelling -th- in German represents the phoneme /t/ or /tʰ/, not the fricative /θ/, standard British pronunciation of "Neanderthal" is with /t/; because of the usual sound represented by digraph ⟨th⟩ in English, "Neanderthal" is pronounced with the voiceless fricative /θ/, at least in "layman's American English". The spelling Neandertal is seen in English in scientific publications. Since "Neanderthal", or "Neandertal", is a common name, there is no authoritative prescription on its spelling, unlike the spelling of the binominal name H. neanderthalensis, predicated by King 1864.
The common name in German is always invariably Neandertaler, not Neandertal, but the spelling of the name of the Neander Valley itself has been affected by the species name, the names of the Neanderthal Museum and of Neanderthal station persisting with pre-1900 orthography. Since the discovery of the Neanderthal fossils, expert opinion has been divided as to whether Neanderthals should be considered a separate species or a subspecies relative to modern humans. Pääbo described such "taxonomic wars" as unresolveable in principle, "since there is no definition of species describing the case." The question depends on the definition of Homo sapiens as a chronospecies, in flux throughout the 20th century. Authorities preferring classification of Neanderthals as subspecies have introduced the subspecies name Homo sapiens sapiens for the anatomically modern Cro-Magnon population which lived in Europe at the same time as Neanderthals, while authorities preferring classification as separate species use Homo sapiens as equivalent to "anatomically modern humans".
During the early 20th century, a prevailing view of Neanderthals as "simian", influenced by Arthur Keith and Marcellin Boule, tended to exaggerate the anatomical differences between Neanderthals and Cro Magnon. Beginning in the 1930s, revised reconstructions of Neanderthals emphasized the similarity rather than differences from modern humans. From the 1940s throughout the 1970s, it was common to use the subspecies classification of Homo sapiens neanderthalensis vs. Homo sapiens sapiens; the hypothesis of "multiregional origin" of modern man was formulated in the 1980s on such grounds, arguing for the presence of an unbroken succession of fossil sites in both Europe and Asia. Hybridization between Neanderthals and Cro Magnon had been suggested on skeletal and craniological grounds since the early 20th century, found increasing support in the 20th century, until Neanderthal admixture was found to be present in modern populations genet
The Aterian is a Middle Stone Age stone tool industry centered in North Africa, but possibly found in Oman and the Thar Desert. The earliest Aterian dates to c. 145,000 years ago, at the site of Ifri n'Ammar in Morocco. However, most of the early dates cluster around the beginning of the Last Interglacial, around 130,000 years ago, when the environment of North Africa began to ameliorate; the Aterian disappeared around 20,000 years ago. The Aterian is distinguished through the presence of tanged or pedunculated tools, is named after the type site of Bir el Ater, south of Tébessa. Bifacially-worked, leaf-shaped tools are a common artefact type in Aterian assemblages, so are racloirs and Levallois flakes and cores. Items of personal adornment are known with an age of 82,000 years; the Aterian is one of the oldest examples of regional technological diversification, evidencing significant differentiation to older stone tool industries in the area described as Mousterian. The appropriateness of the term Mousterian is contested in a North African context, however.
The technological character of the Aterian has been debated for a century, but has until eluded definition. The problems defining the industry have related to its research history and the fact that a number of similarities have been observed between the Aterian and other North African stone tool industries of the same date. Levallois reduction is widespread across the whole of North Africa throughout the Middle Stone Age, scrapers and denticulates are ubiquitous. Bifacial foliates moreover represent a huge taxonomic category and the form and dimension of such foliates associated with tanged tools is varied. There is a significant variation of tanged tools themselves, with various forms representing both different tool types and the degree tool resharpening. More a large-scale study of North African stone tool assemblages, including Aterian assemblages, indicated that the traditional concept of stone tool industries is problematic in the North African Middle Stone Age. Although the term Aterian defines Middle Stone Age assemblages from North Africa with tanged tools, the concept of an Aterian industry obfuscates other similarities between tanged tool assemblages and other non-Aterian North African assemblages of the same date.
For example, bifacial leaf points are found across North Africa in assemblages that lack tanged tools and Levallois flakes and cores are near ubiquitous. Instead of elaborating discrete industries, the findings of the comparative study suggest that North Africa during the Last Interglacial comprised a network of related technologies whose similarities and differences correlated with geographical distance and the palaeohydrology of a Green Sahara. Assemblages with tanged tools may therefore reflect particular activities involving the use of such tool types, may not reflect a substantively different archaeological culture to others from the same period in North Africa; the findings are significant because they suggest that current archaeological nomenclatures do not reflect the true variability of the archaeological record of North Africa during the Middle Stone Age from the Last Interglacial, hints at how early modern humans dispersed into uninhabitable environments. This notwithstanding, the term still usefully denotes the presence of tanged tools in North African Middle Stone Age assemblages.
Tanged tools persisted in North Africa until around 20,000 years ago, with the youngest sites located in Northwest Africa. By this time, the Aterian lithic industry had long ceased to exist in the rest of North Africa due to the onset of the Ice Age, which in North Africa, resulted in hyperarid conditions. Assemblages with tanged tools,'the Aterian', therefore have a significant temporal and spatial range. However, the exact geographical distribution of this lithic industry is uncertain; the Aterian's spatial range is thought to have existed in North Africa up to the Nile Valley Possible Aterian lithic tools have been discovered in Middle Paleolithic deposits in Oman and the Thar Desert. The Aterian is associated with early Homo sapiens at a number of sites in Morocco; some studies of comparative skeletal morphology have suggested that these people exist on the same morphological continuum as the Jebel Irhoud specimens thought to date to 160,000 years ago. The'Aterian' fossils display similarities with the Iberomaurusians and the earliest modern humans found out of Africa at Skhul and Qafzeh in the Levant, they are broadly contemporary to them.
Apart from producing a distinctive and sophisticated stone tool technology, these early North African populations seem to have engaged with symbolically constituted material culture, creating what are amongst the earliest African examples of personal ornamentation. Such examples of shell'beads' have been found far inland, suggesting the presence of long distance social networks. Studies of the variation and distribution of the Aterian have now suggested that associated populations lived in subdivided populations living most of their lives in relative isolation and aggregating at particular times to reinforce social ties; such a subdivided population structure has been inferred from the pattern of variation observed in early African fossils of Homo sapiens. Associated faunal studies suggest that the people making the Aterian exploited coastal resources as well as engaging in hunting; as the points are small and lightweight, it is that they were not hand-delivered but instead thrown. There is no evidence that a spear thrower was used, but the points have characteri
The Gravettian was an archaeological industry of the European Upper Paleolithic that succeeded the Aurignacian circa 33,000 years BP. It is archaeologically the last European culture many consider unified, had disappeared by c. 22,000 BP, close to the Last Glacial Maximum, although some elements lasted until c. 17,000 BP. At this point, it was replaced abruptly by the Solutrean in France and Spain, developed into or continued as the Epigravettian in Italy, the Balkans and Russia, they are known for their Venus figurines, which were made as either ivory or limestone carvings. The Gravettian culture was first identified at the site of La Gravette in Southwestern France; the Gravettians were hunter-gatherers who lived in a bitterly cold period of European prehistory, Gravettian lifestyle was shaped by the climate. Pleniglacial environmental changes forced them to adapt. West and Central Europe were cold during this period. Archaeologists describe two regional variants: the western Gravettian, known from cave sites in France and Britain, the eastern Gravettian in Central Europe and Russia.
The eastern Gravettians, which include the Pavlovian culture, were specialized mammoth hunters, whose remains are found not in caves but in open air sites. Gravettian culture thrived on their ability to hunt animals, they utilized a variety of tools and hunting strategies. Compared to theorized hunting techniques of Neanderthals and earlier human groups, Gravettian hunting culture appears much more mobile and complex, they lived in caves or semi-subterranean or rounded dwellings which were arranged in small "villages". Gravettians are thought to have been innovative in the development of tools such as blunted-back knives, tanged arrowheads and boomerangs. Other innovations include the use of woven nets and oil lamps made of stone. Blades and bladelets were used to make decorations and bone tools from animal remains. Gravettian culture extends across a large geographic region, as far as Estremadura in Portugal, but is homogeneous until about 27,000 BN. They developed burial rites, which included the inclusion of simple, purpose built, offerings and/or personal ornaments owned by the deceased, placed within the grave or tomb.
Surviving Gravettian art includes numerous cave paintings and small, portable Venus figurines made from clay or ivory, as well as jewelry objects. The fertility deities date from the early period, they conform to a specific physical type, with large breasts, broad hips and prominent posteriors. The statuettes tend to lack facial details, their limbs that are broken off. During the post glacial period, evidence of the culture begins to disappear from northern Europe but was continued in areas around the Mediterranean. Animals were a primary food source for early humans of the Gravettian period. Since Europe was cold during this period, food sources needed to be high in energy and fat content. Testing comparisons among various human remains reveal that populations at higher latitudes placed greater dietary emphasis on meat. A defining trait distinguishing Gravettian people was their ease of mobility compared to their Neanderthal counterparts. Modern humans developed the technology and social organization that enabled them to migrate with their food source whereas Neanderthals were not adept at travelling with sedentary herds.
With their ability to move with the herds, Gravettian diets incorporated a huge variety of animal prey. The main factors were the animal's size. For example, first year deer offered hides most suitable for clothing, while fourth year deer contained far more meat. Gravettian diet included larger animals such as mammoths, wolves, reindeer killed with stone or bone tools, as well as hares and foxes captured with nets; this time period is classified by the strong emphasis on meat consumption because agriculture had not been introduced nor utilized. In addition, the climate was not favorable to stable crop cultivation. Coastal Gravettians were able to avail of marine protein. From remains found in Italy and Wales, carbon dating reveals that 20-30% of Gravettian diets of coastal peoples consisted of sea animals. Populations of lower latitudes relied more on shell fish and fish while higher latitudes' diets consisted of seals. Clubs and sticks were the primary hunting tools during the Upper Paleolithic period.
Bone and ivory points have all been found at sites in France. Due to the primitive tools, many animals were hunted at close range; the typical artefact of Gravettian industry, once considered diagnostic, is the small pointed blade with a straight blunt back. They are today known as the Gravette point, were used to hunt big game. Gravettians used nets to hunt small game, are credited with inventing the bow and arrow. Gravettian settlers tended towards the valleys. Examples found through discoveries in Gr. La Gala, a site in Southern Italy, show a strategic settlement based in a small valley; as the settlers became more aware of the migration patterns of animals like red deer, they learned that prey herd in valleys, thereby allowing the hunters to avoid travelling long distances for food. In Gr. La Gala, the glacial topography forced the deer to pass through the areas in the valley occupied by humans. Additional evidence of strategically positioned settlements include sites like Klithi in Greece placed to intercept migrating prey.
Discoveries in the Czech Republic suggest that nets were used to capture large numbers of smaller prey, thus offering a quick and consistent food supp
Swiderian culture published in English literature as Sviderian and Swederian, is the name of an Upper Palaeolithic/Mesolithic cultural complex, centred on the area of modern Poland. The type-site is Świdry Wielkie, in Otwock near the Swider River, a tributary to the Vistula River, in Masovia; the Swiderian is recognized as a distinctive culture that developed on the sand dunes left behind by the retreating glaciers. Rimantiene considered the relationship between Swiderian and Solutrean "outstanding, though indirect", in contrast with the Bromme-Ahrensburg complex, for which she introduced the term "Baltic Magdalenian" for generalizing all other North European Late Paleolithic culture groups that have a common origin in Aurignacian. Three periods can be distinguished; the crude flint blades of Early Swiderian are found in the area of Nowy Mlyn in the Holy Cross Mountains region. The Developed Swiderian appeared with their migrations to the north and is characterized by tanged blades: this stage separates the northwestern European cultural province, embracing Belgium, northwest Germany and Norway, the Middle East European cultural province, embracing Silesia, Poland, Belarus, Central Russia and the Crimea.
Late Swiderian is characterized by blades with a blunted back. The Swiderian culture plays a central role in the Palaeolithic-Mesolithic transition, it has been accepted that most of the Swiderian population emigrated at the end of the Pleistocene to the northeast following the retreating tundra, after the Younger Dryas. Recent radiocarbon dates prove that some groups of the Svidero-Ahrensburgian Complex persisted into the Preboreal. Unlike western Europe, the Mesolithic groups now inhabiting the Polish Plain were newcomers; this has been attested by a 300-year-long gap between the youngest Palaeolithic and the oldest Mesolithic occupation. The oldest Mesolithic site is Chwalim, located in Poland. Thus, the Mesolithic population progressed from the west after a 300-year-long settlement break, moved towards the east; the lack of good flint raw materials in the Polish early Mesolithic has been interpreted thus that the new arriving people were not acquainted yet with the best local sources of flint, proving their external origin.
The Ukrainian archaeologist L. Zalizniak believes Kunda culture of Central Russia and the Baltic zone, other so-called post-Swiderian cultures, derive from the Swiderian culture. Sorokin rejects the "contact" hypothesis of the formation of Kunda culture and holds it originated from the seasonal migrations of Swiderian people at the turn of Pleistocene and Holocene when human subsistence was based on hunting reindeer. Many of the earliest Mesolithic sites in Finland are post-Swiderian; the raw materials of the lithic assemblage at Sujala originate in the Varanger Peninsula in northern Norway. Concerning this region, the held view today is that the earliest settlement of the North Norwegian coast originated in the Fosna culture of the western and southwestern coast of Norway and in the final Palaeolithic Ahrensburg culture of northwestern Europe; the combination of a coastal raw material and a lithic technique typical to Late Palaeolithic and early Mesolithic industries of northern Europe suggested that Sujala was contemporaneous to Phase 1 of the Norwegian Finnmark Mesolithic, dating to between 9 000 and 10 000 BP.
Proposed parallels with the blade technology among the earliest Mesolithic finds in southern Norway would have placed the find closer or before 10 000 BP. However, a preliminary connection to early North Norwegian settlements is contradicted by the shape of the tanged points and by the blade reduction technology from Sujala; the bifacially shaped tang and ventral retouch on the tip of the arrowpoints and the pressure technique used in blade manufacture are rare or absent in Ahrensburgian contexts, but characteristic of the so-called Post-Swiderian cultures of northwestern Russia. There, counterparts of the Sujala cores can be found; the Sujala assemblage is considered unquestionably post-Swiderian and is dated by radiocarbon to 9265-8930 BP, the true age being 8300-8200 CalBC. Such an Early Mesolithic influence from Russia or the Baltic might imply an adjustment to previous thoughts on the colonization of the Barents Sea coast. Ahrensburg culture
Acheulean, from the French acheuléen, is an archaeological industry of stone tool manufacture characterized by distinctive oval and pear-shaped "hand-axes" associated with Homo erectus and derived species such as Homo heidelbergensis. Acheulean tools were produced during the Lower Palaeolithic era across Africa and much of West Asia, South Asia, Europe, are found with Homo erectus remains, it is thought that Acheulean technologies first developed about 1.76 million years ago, derived from the more primitive Oldowan technology associated with Homo habilis. The Acheulean includes at least the early part of the Middle Paleolithic, its end is not well defined, depending on whether Sangoan is included, it may be taken to last until as late as 130,000 years ago. In Europe and Western Asia, early Neanderthals adopted Achaeulean technology, transitioning to Mousterian by about 160,000 years ago; the type site for the Acheulean is Saint-Acheul, a suburb of Amiens, the capital of the Somme department in Picardy, where artifacts were found in 1859.
John Frere is credited as being the first to suggest a ancient date for Acheulean hand-axes. In 1797, he sent two examples to the Royal Academy in London from Hoxne in Suffolk, he had found them in prehistoric lake deposits along with the bones of extinct animals and concluded that they were made by people "who had not the use of metals" and that they belonged to a "very ancient period indeed beyond the present world". His ideas were, ignored by his contemporaries, who subscribed to a pre-Darwinian view of human evolution. Jacques Boucher de Crèvecœur de Perthes, working between 1836 and 1846, collected further examples of hand-axes and fossilised animal bone from the gravel river terraces of the Somme near Abbeville in northern France. Again, his theories attributing great antiquity to the finds were spurned by his colleagues, until one of de Perthe's main opponents, Dr Marcel Jérôme Rigollot, began finding more tools near Saint Acheul. Following visits to both Abbeville and Saint Acheul by the geologist Joseph Prestwich, the age of the tools was accepted.
In 1872, Louis Laurent Gabriel de Mortillet described the characteristic hand-axe tools as belonging to L'Epoque de St Acheul. The industry was renamed as the Acheulean in 1925. Providing calendrical dates and ordered chronological sequences in the study of early stone tool manufacture is accomplished through one or more geological techniques, such as radiometric dating potassium-argon dating, magnetostratigraphy. From the Konso Formation of Ethiopia, Acheulean hand-axes are dated to about 1.5 million years ago using radiometric dating of deposits containing volcanic ashes. Acheulean tools in South Asia have been found to be dated as far as 1.5 million years ago. However, the earliest accepted examples of the Acheulean known come from the West Turkana region of Kenya and were first described by a French-led archaeology team; these particular Acheulean tools were dated through the method of magnetostratigraphy to about 1.76 million years ago, making them the oldest not only in Africa but the world.
The earliest user of Acheulean tools was Homo ergaster, who first appeared about 1.8 million years ago. Not all researchers use this formal name, instead prefer to call these users early Homo erectus. From geological dating of sedimentary deposits, it appears that the Acheulean originated in Africa and spread to Asian, Middle Eastern, European areas sometime between 1.5 million years ago and about 800 thousand years ago. In individual regions, this dating can be refined; however more recent research demonstrated that hand-axes from Spain were made more than 900,000 years ago. Relative dating techniques suggest that Acheulean tools followed on from earlier, cruder tool-making methods, but there is considerable chronological overlap in early prehistoric stone-working industries, with evidence in some regions that Acheulean tool-using groups were contemporary with other, less sophisticated industries such as the Clactonian and later with the more sophisticated Mousterian, as well, it is therefore important not to see the Acheulean as a neatly defined period or one that happened as part of a clear sequence but as one tool-making technique that flourished well in early prehistory.
The enormous geographic spread of Acheulean techniques makes the name unwieldy as it represents numerous regional variations on a similar theme. The term Acheulean does not represent a common culture in the modern sense, rather it is a basic method for making stone tools, shared across much of the Old World; the earliest Acheulean assemblages contain numerous Oldowan-style flakes and core forms and it is certain that the Acheulean developed from this older industry. These industries are known as the Developed Oldowan and are certainly transitional between the Oldowan and Acheulean. In the four divisions of prehistoric stone-working, Acheulean artefacts are classified as Mode 2, meaning they are more advanced than the Mode 1 tools of the Clactonian or Oldowan/Abbevillian industries but lacking the sophistication of the Mode 3 Middle Palaeolithic technology, exemplified by the Mousterian industry; the Mode 1 industries created rough flake tools by hitting a suitable stone with a hammerstone. The resulting flake that broke off would have a natural sharp edge for cutting and could afterwards be sharpened further by striking another smaller flake from the edge if necessary
Marine isotope stage
Marine isotope stages, marine oxygen-isotope stages, or oxygen isotope stages, are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data reflecting changes in temperature derived from data from deep sea core samples. Working backwards from the present, MIS 1 in the scale, stages with numbers have high levels of oxygen-18 and represent cold glacial periods, while the odd-numbered stages are troughs in the oxygen-18 figures, representing warm interglacial intervals; the data are derived from pollen and foraminifera remains in drilled marine sediment cores and other data that reflect historic climate. The MIS timescale was developed from the pioneering work of Cesare Emiliani in the 1950s, is now used in archaeology and other fields to express dating in the Quaternary period, as well as providing the fullest and best data for that period for paleoclimatology or the study of the early climate of the Earth, representing "the standard to which we correlate other Quaternary climate records".
Emiliani's work in turn depended on Harold Urey's prediction in a paper of 1947 that the ratio between oxygen-18 and oxygen-16 isotopes in calcite, the main chemical component of the shells and other hard parts of a wide range of marine organisms, should vary depending on the prevailing water temperature in which the calcite was formed. Over 100 stages have been identified, going back some 6 million years, the scale may in future reach back up to 15 mya; some stages, in particular MIS 5, are divided into sub-stages, such as "MIS 5a", with 5 a, c, e being warm and b and d cold. A numeric system for referring to "horizons" may be used, with for example MIS 5.5 representing the peak point of MIS 5e, 5.51, 5.52 etc. representing the peaks and troughs of the record at a still more detailed level. For more recent periods precise resolution of timing continues to be developed. In 1957 Emiliani moved to the University of Miami to have access to core-drilling ships and equipment, began to drill in the Caribbean and collect core data.
A further important advance came in 1967, when Nicholas Shackleton suggested that the fluctuations over time in the marine isotope ratios that had become evident by were caused not so much by changes in water temperature, as Emiliani thought, but by changes in the volume of ice-sheets, which when they expanded took up the lighter oxygen-16 isotope in preference to the heavier oxygen-18. The cycles in the isotope ratio were found to correspond to terrestrial evidence of glacials and interglacials. A graph of the entire series of stages revealed unsuspected advances and retreats of ice and filled in the details of the stadials and interstadials. More recent ice core samples of today's glacial ice substantiated the cycles through studies of ancient pollen deposition. A number of methods are making additional detail possible. Matching the stages to named periods proceeds as new dates are discovered and new regions are explored geologically; the marine isotopic records appear more complete and detailed than any terrestrial equivalents, have enabled a timeline of glaciation for the Plio-Pleistocene to be identified.
It is now believed that changes in the size of the major ice sheets such as the historical Laurentide ice sheet of North America are the main factor governing variations in the oxygen isotope ratios. The MIS data matches the astronomical data of Milankovitch cycles of orbital forcing or the effects of variations in insolation caused by cyclical slight changes in the tilt of the earth's axis of rotation – the "orbital theory". Indeed, that the MIS data matched Milankovich's theory, which he formed during World War I, so well was a key factor in the theory gaining general acceptance, despite some remaining problems at certain points, notably the so-called 100,000-year problem. For recent periods data from radiocarbon dating and dendrochronology support the MIS data; the sediments acquire depositional remanent magnetization which allows them to be correlated with earth's geomagnetic reversals. For older core samples, individual annual depositions cannot be distinguished, dating is taken from the geomagnetic information in the cores.
Other information as to the ratios of gases such as carbon dioxide in the atmosphere, is provided by analysis of ice cores. The SPECMAP Project, funded by the US National Science Foundation, has produced one standard chronology for oxygen isotope records, although there are others; this high resolution chronology was derived from several isotopic records, the composite curve was smoothed and tuned to the known cycles of the astronomical variables. The use of a number of isotopic profiles was designed to eliminate'noise' errors, that could have been contained within a single isotopic record. Another large research project funded by the US government in the 1970s and 1980s was Climate: Long range Investigation and Prediction, which to a large degree succeeded in its aim of producing a map of the global climate at the Last Glacial Maximum, some 18,000 years ago, with some of the research directed at the climate some 120,000 years ago, during the last interglacial; the theoretical advances and improved data available by the 1970s enabled a "grand synthesis" to be made, best known from the 1976 paper Variations in the earth’s orbit: pacemaker of the ice ages, by J.
D. Hays and John Imbrie, still widely accepted today, covers the MIS timescale and the causal effect of the orbital theory. In 2010 the Subcommission on Quaternary Stratigraphy of the Inte