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128-531: Although today the western Egyptian desert is totally dry, this was not always the case. There is good evidence that there were several humid periods in the past (when up to 500 mm of rain would fall per year), the most recent one during the last interglacial and early last glaciation periods which stretched between 130,000 and 70,000 years ago. During this time, the area was a savanna and supported numerous animals such as extinct buffalo and large giraffes, varieties of antelope and gazelle. Beginning around

256-668: A dominance of grasses over humid tropics trees. The tree Lophira alata and others may have spread out of the African forests during the AHP, and the Lactuca plants may have split into two species under the effects of the AHP and other climate changes in Africa during the Holocene. The Sahara climate did not become entirely homogeneous; its central-eastern parts were probably drier than

384-447: A dry to a "green" Sahara and back have threshold behaviour, with the change occurring once a certain level of insolation is exceeded; likewise, a gradual drop of insolation often leads to a sudden transition back to a dry Sahara. This is due to various feedback processes which are at work, and in climate models there is often more than one stable climate-vegetation state. Sea surface temperature and greenhouse gas changes synchronized

512-541: A gradual advance is supported by tephrochronological data. Likewise, in the Sahara there might have been a delay of about a millennium between the onset of the AHP and the full establishment of humid conditions, as vegetation growth and the filling of river systems took time. Lake Victoria reappeared and overflowed; Lake Albert also overflowed into the White Nile 15,000–14,500 years ago and so did Lake Tana , into

640-538: A large number of icebergs in the North Atlantic; the discharge of large amounts of such icebergs between 11,500 and 21,000 years before present coincided with droughts in the subtropics . Before the onset of the AHP, it is thought that Lake Victoria , Lake Albert , Lake Edward , Lake Turkana and the Sudd swamps had dried out. The White Nile had become a seasonal river whose course along with that of

768-688: A massive volcanic landslide off Mount Etna , Sicily , caused a megatsunami that devastated the eastern Mediterranean coastline on the continents of Asia, Africa and Europe. In South America, a large eruption occurred at Cueros de Purulla c. 5870 BC, forming a buoyant cloud and depositing the Cerro Paranilla Ash in the Calchaquí Valleys . A cataclysmic volcanic eruption occurred c. 5700 BC in Oregon when 12,000-foot (3,700 m) high Mount Mazama created Crater Lake as

896-495: A misnomer as the spaces between the pairs of stones in the gates are a bit too wide, and the distances between the gates are too short for accurate calendar measurements." An inventory of Egyptian archaeoastronomical sites for the UNESCO World Heritage Convention evaluated Nabta Playa as having "hypothetical solar and stellar alignments." Astrophysicist Thomas G. Brophy suggests the hypothesis that

1024-597: A new, more organised group began to use the site, burying cattle in clay-lined chambers and building other tumuli. Around 4800 BC a stone circle was constructed, with narrow slabs approximately aligned with the summer solstice, near the beginning of the rainy season. More complex structures followed during a megalith period the researchers dated to between about 4500 BC to 3600 BC. Using their original measurements, complemented by satellite imagery and GPS measurements by Brophy and Rosen, they confirmed possible alignments with Sirius, Arcturus , Alpha Centauri , and

1152-476: A northward movement of the ITCZ and increasing moisture gradients between land and sea. Two temperature gradients, one between a cooler Atlantic during spring and an already warming African continent, the other between warmer temperatures north of 10° latitude and cooler south, may have assisted in this change. In Eastern Africa, ITCZ changes had relatively little effect on precipitation changes. The past position of

1280-479: A novel number system and the domestic pig from Indo-Europeans in the south. Similarly, the Indo-Europeans themselves had acquired such words and cultural items from peoples and cultures to their south or west, including possibly their words for "ox", *gʷou- (compare English cow ) and "grain", *bʰars- (compare English barley ). In contrast, basic vocabulary – words such as "me", "hand", "water", and "be" –

1408-645: A number of dry/wet periods have been defined for the Central Africa region. In general, these types of climate fluctuations between wetter and drier periods are known as " pluvials " and " interpluvials ", respectively. The term "Green Sahara" is frequently used to describe the AHPs. Because the AHP did not affect all of Africa and is thus not technically accurate, some scientists have instead used and recommended "North African humid period" and "Northern African humid period". Other terms that have been applied to

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1536-497: A rising azimuth exactly on the C-line average". However, according to Malville, Schild et al. (2007) the dates proposed by Brophy are inconsistent with the archaeological evidence, and "inference in archaeoastronomy must always be guided and informed by archaeology, especially when substantial field work has been performed in the region". They also concluded that, on closer inspection, the C-line of megaliths "consists of stones resting on

1664-503: A role in vegetation changes. Isotope ratios such as the hydrogen / deuterium ratio that have been used to reconstruct past precipitation values likewise are under the influence of various physical effects, which complicates their interpretation. Most records of Holocene precipitation in eastern Africa come from low altitudes. The term "African humid period" (AHP) was coined in 2000 by Peter B. de Menocal et al. Earlier humid periods are sometimes known as "African humid periods" and

1792-564: A team of archaeologists, excavated a series of Holocene pottery from Nabta Playa which represented the earliest phase of ceramic production in the Saharan region and were described as "relatively sophisticated bowls decorated with a toothed wheel". Also, they argued that the pottery from the region had an important role in shaping the cultural development of the Eastern Sahara during the early Holocene period. The authors concluded that it

1920-721: Is "likely that the Early Holocene colonisers of the southern Western Desert, the El Adam hunter-gatherer-cattle keepers, came to the south-eastern fringes of the Sahara from the Nile Valley " and shared an "almost identical" output of technology with the Arkinian culture in Lower Nubia . African humid period The African humid period (AHP; also known by other names ) is a climate period in Africa during

2048-517: Is also known as " aqualithic " although substantial differences between the cultures of various places have been found. The greening of the Sahara led to a demographic expansion and especially in the Eastern Sahara human occupancy coincides with the AHP. Conversely occupation decreased along the Nile valley, perhaps due to the expansion of wetlands there and frequent large-scale flooding of

2176-407: Is an important factor in the precipitation increase. Specifically, increased precipitation increases the amount of vegetation; vegetation absorbs more sunlight and thus more energy is available for the monsoon. In addition, evapotranspiration from vegetation adds more moisture, although this effect is less pronounced than the albedo effect. Heat fluxes in the soil and evaporation are also altered by

2304-527: Is much less readily borrowed between languages. If Indo-European and Uralic are genetically related, there should be agreements regarding basic vocabulary, with more agreements if they are closely related, fewer if they are less closely related. - Indo-European cultures in Central Asia flourish, these cultures are the: Middle Volga culture (followed by the Samara culture at the turn of the millennium),

2432-1076: Is possible that giant lakes only formed in the southern part of the Sahara. Other lakes are known from Adrar Bous in Niger , Era Kohor and Trou au Natron in the Tibesti Mountains , I-n-Atei in the Hoggar , at Ine Sakane and in Taoudenni in Mali , the Garat Ouda and Takarkori Lakes in the Acacus Mountains , Chemchane in Mauretania , at Guern El Louläilet in the Great Western Erg and Sebkha Mellala close to Ouargla , both in Algeria , at Wadi Shati and elsewhere in

2560-525: Is supported by the frequent depiction of cattle in rock paintings . The relative importance of hunter-gatherer practices and pastoralism, and whether people were sedentary or migratory, is unclear. The Dufuna canoe , one of the oldest known ships in the world, appears to date to the Holocene humid period and implies that the waterbodies of that time were navigated by humans. The cultural units "Masara" and "Bashendi" existed in Dakhleh Oasis during

2688-636: Is the Cave of Swimmers in the Gilf Kebir mountains of Egypt; other well known sites are the Gabal El Uweinat mountains also of Egypt, Arabia and the Tassili n'Ajjer in Algeria where rock paintings from this time have been discovered. Humans also left artifacts such as Fesselsteine and ceramics in what today are inhospitable deserts. North Africa together with East Asia is one of

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2816-475: Is the fifth millennium alignments of stele to bright stars. They conclude their report by writing that "The symbolism embedded in the archaeological record of Nabta Playa in the Fifth Millennium BC is very basic, focussed on issues of major practical importance to the nomads: cattle, water, death, earth, sun and stars." In 2011, Maciej Jórdeczka, Halina Królik, Mirosław Masojć and Romuald Schild,

2944-518: Is the most profound climate change of the low latitudes during the last 100,000 years and stands out within the otherwise relatively climatically stable Holocene. It is part of the so-called Holocene climatic optimum and coincides with a global warm phase, the Holocene Thermal Maximum . Liu et al. 2017 subdivided the humid period into an "AHP I" which lasted until 8,000 years ago, and an "AHP II" from 8,000 years onward, with

3072-475: The 10th millennium BC , this region of the Nubian Desert began to receive more rainfall, filling a lake. Early people may have been attracted to the region due to the source of water. Archaeological findings indicate the presence of small seasonal camps in the region dating to the 9th – 8th millennia BC . Fred Wendorf , the site's discoverer, and ethno-linguist Christopher Ehret have suggested that

3200-656: The 5th millennium BC these peoples fashioned what may be among the world's earliest known archeoastronomical devices (roughly contemporary to the Goseck circle in Germany and the Mnajdra megalithic temple complex in Malta). These include alignments of stones that may have indicated the rising of certain stars and a " calendar circle" that indicates the approximate direction of summer solstice sunrise. "Calendar circle" may be

3328-478: The 6th millennium BC , evidence of a prehistoric religion or cult appears. From 5500 BC the Late Neolithic period began, with "a new group that had a complex social system expressed in a degree of organisation and control not previously seen." These new people were responsible for sacrificial cattle burials in clay -lined and roofed chambers covered by rough stone tumuli. It has been suggested that

3456-661: The Air Mountains . Ephemeral lakes developed between dunes, and a "freshwater archipelago" appears to have existed in the Murzuq basin. All these lake systems left fossils such as fish, limnic sediments and fertile soils that were later used for agriculture (El Deir, Kharga Oasis ). Finally, crater lakes formed in volcanic fields such as Trou au Natron and Era Kohor in the Tibesti, and sometimes survive to this day as smaller remnant lakes such as Malha crater in

3584-584: The Blue Nile . The White Nile flooded part of its valley and reconnected to the main Nile. In Egypt widespread flooding by the "Wild Nile" took place; this "Wild Nile" period led to the largest recorded floods on this river, sedimentation in floodplains, and probably also impacted human populations along the river. Even earlier, 17,000–16,800 years ago, meltwater from glaciers in Ethiopia – which were retreating at that time – may have begun to increase

3712-562: The Bodélé Depression and perhaps as much as 8% of the present-day Sahara desert. It influenced the climate itself; for example rainfall would have been reduced at the centre of the lake and increased at its margins. Lake Chad was possibly fed from the north by rivers draining the Hoggar (Taffassasset drainage) and Tibesti Mountains, from the Ennedi Mountains in the east through the "Eastern palaeorivers" and from

3840-616: The Congo Air Boundary or increased convergence along this boundary may have contributed; the Congo Air Boundary would have been shifted east by the stronger westerly winds directed by lower atmospheric pressure over Northern Africa, allowing additional moisture from the Atlantic to reach East Africa. The parts of East Africa that were isolated from Atlantic moisture did not become significantly wetter during

3968-736: The Dnieper-Donets , the Narva (eastern Baltic), the Ertebølle (Denmark and northern Germany), and the Swifterbant (Low Countries). They were linked by a common pottery style that had spread westward from Asia and is sometimes called " ceramic Mesolithic ", distinguishable by a point or knob base and flared rims. - According to Vasily Radlov , among the Paleo-Siberian inhabitants of Central Siberia and Southern Siberia were

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4096-801: The Grand Erg Occidental . Wetlands also expanded during the AHP, but both their expansion and subsequent retreat were slower than that of lakes. The Niger River , which had been dammed by dunes during the LGM, formed a lake in the Timbuktu region that eventually overflowed and drained at some point during the AHP. In some parts of the Sahara ephemeral lakes formed such as at Abu Ballas , Bir Kiseiba , Bir Sahara , Bir Tarfawi and Nabta Playa in Egypt, which may relate to later Egyptian religions, or swamp -lakes such as at Adrar Bous close to

4224-588: The Holocene AHP or correlative climate phases are "Holocene humid period", which also covers an analogous episode in Arabia and Asia; "early to mid-Holocene humid episode"; "Holocene Pluvial"; "Holocene Wet Phase"; " Kibangien A " in Central Africa; "Makalian" for the Neolithic period of northern Sudan; "Nabtian Pluvial", "Nabtian Wet Phase" or "Nabtian period" for the 14,000–6,000 humid period over

4352-684: The Mayo Kebbi and the Benue River , eventually reaching the Gulf of Guinea . Older dune systems were submerged by Lake Chad. Among the large lakes which may have formed in the Sahara are Lake Megafezzan in Libya and Lake Ptolemy in Sudan. Quade et al. 2018 raised some doubts about the size and existence of some of these lakes such as Lake Ptolemy, Lake Megafezzan, Lake Ahnet-Mouydir ; it

4480-517: The Meidob volcanic field . Potentially, the increased availability of water during the AHP may have facilitated the onset of phreatomagmatic eruptions such as maar formation in the Bayuda volcanic field , although the chronology of volcanic eruptions there is not well known enough to substantiate a link to the AHP. Increased precipitation resulted in the formation or reactivation of river systems in

4608-455: The Nile Valley . The people of Nabta Playa had villages with 'planned' layouts, with deep wells that held water year-round. Findings also indicate that the region was occupied only seasonally, most likely only in the summer , when the local lake had adequate water for grazing cattle . Comparative research suggests the indigenous inhabitants may have a significantly more advanced knowledge of astronomy than previously thought possible. By

4736-509: The Nile crocodile and the fish Clarias gariepinus and Tilapia zillii . It is possible that the name Tassili n'Ajjer , which means "plateau of the rivers" in Berber , is a reference to past river flows. On the other hand, intense flows of these rivers may have made their shores dangerous to humans and thus created additional impetus for human movement. Now-dry river valleys from the AHP in

4864-592: The North American cultures to this day. - Na-Dené -speaking peoples finally entered North America starting around 8000  BCE , reaching the Pacific Northwest by 5000  BCE , and from there migrating along the Pacific Coast and into the interior. Linguists, anthropologists, and archeologists believe their ancestors constituted a separate migration into North America, later than

4992-732: The North Atlantic and the Mediterranean Sea towards the Mediterranean coasts of Africa. There were complex interactions with the atmospheric circulation of the extratropics and between moisture coming from the Atlantic Ocean and the Indian Ocean , and an increased overlap between the areas wetted by the monsoon and those wetted by extratropical cyclones . Climate models indicate that changes from

5120-658: The Northern Hemisphere while decreasing it in the Southern Hemisphere . According to climate modelling , orbital changes by themselves cannot increase precipitation over Africa enough to explain the formation of the large desert lakes such as 330,000 square kilometres (130,000 sq mi) Lake Megachad , the climate proxies for precipitation, or the northward expansion of vegetation unless ocean and land surface changes are factored in. Decreasing albedo resulting from vegetation changes

5248-580: The Sudanese region . Pottery decorations included complex patterns of impressions applied with a comb in a rocking motion. Joel D. Irish (2001), reported in "Holocene Settlement of the Egyptian Sahara", based on osteological and dental data suggested a mainly sub-Saharan African affinity and origin at Nabta (with sub-Saharan tendencies most commonly detected), but also possible North African tendencies, concluding that, "Henneberg et al. suggest that

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5376-565: The Ténéré desert a cemetery has been found, which has been used to reconstruct the lifestyle of these former inhabitants of the Sahara, and at Lake Ptolemy in Nubia humans settled close to the lake shore, using its resources and perhaps even engaging in leisure activities. At that time, many humans appear to have depended on water-bound resources, seeing as many of the tools left by the early humans are associated with fishery ; hence this culture

5504-664: The Yeniseians , of whom the Kets are considered the last remainder of these peoples. The Yeniseians were followed by the Uralic Samoyeds , who came from the northern Ural region. Proto-Uralic is the unattested reconstructed language ancestral to the modern Uralic language family . The hypothetical language is thought to have been originally spoken in a small area in about 7000–2000 BC, and expanded to give differentiated Proto-Languages . Some newer research has pushed

5632-407: The Younger Dryas and the short 8.2 kiloyear event . The African humid period ended 6,000–5,000 years ago during the Piora Oscillation cold period. While some evidence points to an end 5,500 years ago, in the Sahel , Arabia and East Africa, the end of the period appears to have taken place in several steps, such as the 4.2-kiloyear event . The AHP led to a widespread settlement of the Sahara and

5760-416: The last glacial maximum , the latter is equivalent to the "Kanemian"; "Kanemian dry period" refers to a dry period between 20,000 and 13,000 years before present in the Lake Chad area. The African humid period took place in the late Pleistocene and early-middle Holocene , and saw increased precipitation in Northern and Western Africa due to a northward migration of the tropical rainbelt. The AHP

5888-970: The rain shadows of mountains and could have supported arid climate vegetation, explaining the presence of its pollen in sediment cores . In addition, north–south gradations in vegetation patterns have been reconstructed from charcoal and pollen data. Fossils record changes in the animal fauna of the Sahara. This fauna included antelopes , baboons , cane rats , catfish , clams , cormorants , crocodiles, elephants, frogs, gazelles , giraffes , hartebeest , hares , hippos , molluscs , Nile perches , pelicans , rhinoceroses , snake-eagles , snakes, tilapia , toads , turtles and many more animals, and in Egypt there were African buffaloes , spotted hyenas , warthogs , wildebeest and zebra . Additional birds include brown-necked raven , coot , common moorhen , crested grebe , glossy ibis , long-legged buzzard , rock dove , spur-winged goose and tufted duck . Large herds of animals lived in

6016-407: The " Proto-Uralic homeland " east of the Ural Mountains into Western Siberia . - Polities harbouring the Uralic peoples thrive. The shores of all Siberian lakes, which filled the depressions during the Lacustrine period , abound in remains dating from the Neolithic age. Countless kurgans ( tumuli ), furnaces, and other archaeological artifacts bear witness to a dense population. Some of

6144-470: The 6th millennium. Global water levels had risen by about 60 metres due to deglaciation of ice masses since the end of the Last Ice Age. Accelerated rises in sea level rise, called meltwater pulses, occurred three times during the EHSLR. The last one, Meltwater Pulse 1C, which peaked c. 6000 BC, produced a rise of 6.5 metres in only 140 years. It is believed that the cause was a major ice sheet collapse in Antarctica. Approximately 8,000 years ago (c. 6000 BC),

6272-435: The AHP although at one site in Somalia the seasonality of precipitation may or may not have decreased. Various contributing factors may have led to the increased humidity in East Africa, not all of which were necessarily operating simultaneously during the AHP. That the "African humid period" reached this part of Africa has been doubted. Finally, increased greenhouse gas concentrations may have been involved in directing

6400-433: The AHP has been described as a mosaic between various vegetation types of semi-desert and humid origin rather than a simple northward displacement of plant species, and some brown or yellow vegetation communities persisted. There was no southward displacement of Mediterranean plants during the Holocene and on the Tibesti Mountains cold temperatures may have restricted the expansion of tropical plants. Pollen data often show

6528-437: The AHP has been used as an experiment in the Paleoclimate Modelling Intercomparison Project . Most recently, the effects of the Sahara greening on other continents has drawn scientific attention. The concept of a Sahara significantly different than today, and the rich record it left, has driven the imagination of the public and scientists alike. While the precipitation changes since the last glacial cycle are well established,

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6656-435: The AHP. In Egypt, some rivers active during the AHP are now gravel ridges. In the Air , Hoggar and Tibesti Mountains, the so-called "Middle Terrace " was emplaced at this time. The rivers of the Sahara, lakes and their watersheds may have acted as pathways for the spread of humans and animals; the rivers were often connected to each other by alluvial fans . Proposed examples of animals that spread through rivers are

6784-401: The AHP. In the Acacus Mountains, several cultural horizons known as Early and Late Acacus and Early, Middle, Late and Final Pastoral have been identified while in Niger the Kiffian culture has been related to the beginning of the AHP. Ancient civilizations thrived, with farming and animal husbandry taking place in Neolithic settlements. Possibly, the domestication of plants in Africa

6912-457: The Arabian Deserts, and had a profound effect on African cultures, such as the birth of the Ancient Egyptian civilization . People in the Sahara lived as hunter-gatherers and domesticated cattle, goats and sheep. They left archaeological sites and artifacts such as one of the oldest ships in the world , and rock paintings such as those in the Cave of Swimmers and in the Acacus Mountains . Earlier humid periods in Africa were postulated after

7040-419: The Belt of Orion. They suggest that there are three pieces of evidence suggesting astronomical observations by the herdsmen using the site, which may have functioned as a necropolis . "The repetitive orientation of megaliths, stele, human burials and cattle burials reveals a very early symbolic connection to the north." Secondly, there is the orientation of the cromlech mentioned above. The third piece of evidence

7168-410: The Eastern Mediterranean and Levant ; " Neolithic pluvial "; "Neolithic Subpluvial"; "Neolithic wet phase"; " Nouakchottien " of the Western Sahara 6,500 – 4,000 years before present; "Subpluvial II" and " Tchadien " in the Central Sahara 14,000 – 7,500 years before present. The terms "Big Dry", " Léopoldvillien " and Ogolien  [ fr ] have been applied to the dry period in

7296-435: The Far East. In much of the world, however, including Northern and Western Europe, people still lived in scattered Palaeolithic / Mesolithic hunter-gatherer communities. The world population is believed to have increased sharply, possibly quadrupling, as a result of the Neolithic Revolution . It has been estimated that there were perhaps forty million people worldwide at the end of this millennium, growing to 100 million by

7424-401: The Fezzan in Libya , at Bilma, Dibella, Fachi and Gobero in the Ténéré , Seeterrassental in Niger and at "Eight Ridges", El Atrun, Lake Gureinat, Merga, "Ridge", Sidigh, at Wadi Mansurab, Selima and Oyo in Sudan. The lakes of Ounianga merged into two large lakes and overflowed, either above surface or underground. Mosaics of small lakes developed in some regions, such as

7552-426: The ITCZ in Arabia is also contentious. The African humid period that took place in East Africa appears to have been caused by different mechanisms. Among the proposed mechanisms are decreased seasonality of precipitation due to increased dry season precipitation, shortening of the dry season, increased precipitation and increased inflow of moisture from the Atlantic and Indian Oceans. The Atlantic moisture inflow

7680-603: The Jebel Marra and Tibesti Mountains between 15,000 and 14,000 years ago and the youngest stage of glaciation in the High Atlas mountains took place at the same time as the Younger Dryas and early African humid period. Around 14,500 years ago, lakes started to appear in the arid areas. The humid period began about 15,000 –14,500 years ago. The onset of the humid period took place almost simultaneously over all of Northern and Tropical Africa, with impacts as far as Santo Antão on Cape Verde . In Arabia, wet conditions apparently took about two millennia to advance northward,

7808-434: The Mediterranean coast and the Nile Valley. The aridity during the Last Glacial Maximum appears to have been the consequence of the colder climate and larger polar ice sheets , which squeezed the monsoon belt to the equator and weakened the West African Monsoon. The atmospheric water cycle and the Walker and Hadley circulations were weaker as well. Exceptional dry phases are linked to Heinrich events when there are

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7936-405: The Middle Bronze Age c. 1600 BC. It has been estimated that humans first settled in Malta c. 5900 BC, arriving across the Mediterranean from both Europe and North Africa. Use of pottery found near Tbilisi is evidence that grapes were being used for winemaking c. 5980 BC. Evidence of cheese -making in Poland is dated c. 5500 BC. Four identified cultures starting around 5300 BC were

8064-446: The Nabta Playa people may have been most similar to Negroes from south of the Sahara. The present qualitative dental comparison tentatively supports this conclusion.". Some researchers, including Christopher Ehret, have suggested a Nilo-Saharan linguistic affinity for the Nabta people. Archaeological discoveries reveal that these New Stone Age peoples seem to have lived more organized lives than their contemporaries nearer to and in

8192-420: The Nile delta. Humans were hunting large animals with weapons that have been found in archaeological sites and wild cereals occurring in the Sahara during the AHP such as brachiaria , sorghum and urochloa were an additional source of food. Humans also domesticated cattle , goats and sheep . Cattle domestication may have occurred especially in the more environmentally variable Eastern Sahara, where

8320-432: The Pontic-Caspian steppes by around 4500 BCE (the Kurgan hypothesis ) and that Uralic speakers may have been established in the Pit-Comb Ware culture to their north in the fifth millennium BCE (Carpelan & Parpola 2001:79). Such words as those for "hundred", "pig", and "king" have something in common: they represent "cultural vocabulary" as opposed to "basic vocabulary". They are likely to have been acquired along with

8448-599: The Sahara and consisted of an open grass savannah with shrubs and trees, with a moist savanna vegetation getting established in the mountains. In general, the vegetation expanded northward to 27 – 30° northern latitude in West Africa with a Sahel boundary at about 23° north, as the Sahara was populated by plants that today often occur about 400–600 kilometres (250–370 mi) farther south. The northward movement of vegetation took some time and some plant species moved faster than others. Plants that perform C3 carbon fixation became more common. The fire regime of

8576-420: The Sahara. Some animals expanded over the whole desert, while others were limited to places with deep water. Earlier humid periods in the Sahara may have allowed species to cross the now-desert. A reduction in open grasslands at the beginning of the AHP may explain the decline of the populations of some mammals during and a population bottleneck in cheetahs at the start of the humid period, while leading to

8704-490: The Sahara. The large Tamanrasset River flowed from the Atlas Mountains and Hoggar westward towards the Atlantic and entered it in the Bay of Arguin in Mauritania . It once formed the 12th largest watershed in the world and left a submarine canyon and riverine sediments. Together with other rivers it formed estuaries and mangroves in the Bay of Arguin. Other rivers in the same area also formed submarine canyons, and sediment patterns in marine sediment cores and

8832-656: The Senegal River expanded its riverbed, breached dunes and re-entered the Atlantic Ocean. During the African humid period, lakes, rivers, wetlands and vegetation including grass and trees covered the Sahara and Sahel creating a "Green Sahara" with a land cover that has no modern analogues. Evidence includes pollen data, archaeological sites, evidence of faunal activity such as diatoms , mammals , ostracods , reptiles and snails , buried river valleys , organic-rich mats , mudstones , evaporites as well as travertines and tufas deposited in subaqueous environments. The vegetation cover then extended over almost all of

8960-492: The Yangshao culture spread westward to the Majiayao culture , and then further to Xinjiang and Central Asia along a proto-Silk Road. Indigenous Australians in what is now southwestern Victoria were farming and smoking eels as a food source and trade good using stone weirs, canals, and woven traps around 6000 BC. The 6th Millennium features widespread dramatic climatic events: The early Holocene sea level rise (EHSLR), which began c.10,000 BC, tailed off during

9088-422: The archaeological record." They propose that the area was first used as what they call a "regional ceremonial centre" around 6100 BC to 5600 BC with people coming from various locations to gather on the dunes surrounding the playa where there is archaeological evidence for gatherings that involved large numbers of cattle bones, as cattle were normally only killed on important occasions. Around 5500 BC

9216-768: The associated cattle cult indicated in Nabta Playa marks an early evolution of Ancient Egypt 's Hathor cult . For example, Hathor was worshipped as a nighttime protector in desert regions (see Serabit el-Khadim ). To directly quote professors Wendorf and Schild: ... there are many aspects of political and ceremonial life in prehistoric Egypt and the Old Kingdom that reflects a strong impact from Saharan cattle pastoralists  ... Rough megalithic stone structures buried underground are also found in Nabta Playa, one of which included evidence of what Wendorf described as perhaps "the oldest known sculpture in Egypt." In

9344-477: The beginning of the AHP across Africa. The African humid period has been explained by increased insolation during Northern Hemisphere summer. Due to precession , the season at which Earth passes closest to the Sun on its elliptical orbit – the perihelion – changes, with maximum summer insolation occurring when this happens during Northern Hemisphere summer. Between 11,000 and 10,000 years ago, Earth passed through

9472-474: The circle was constructed and used circa the later date, and the dual date representation was a conceptual representation of the motion of the sky over a precession cycle. Near the Calendar Circle, which is made of smaller stones, there are alignments of large megalithic stones. The southerly lines of these megaliths, Brophy argues, aligned to the same stars as represented in the Calendar Circle, all at

9600-527: The concept of a Green Sahara in the 1930s. Later in the 20th century, conclusive evidence of a past greener Sahara, the existence of lakes and higher Nile flow levels was increasingly reported and it was recognized that the Holocene featured a humid period in the Sahara. The idea that changes in Earth's orbit around the Sun influence the strength of the monsoons was already advanced in 1921, and while

9728-577: The contemporary Dnieper–Donets culture . From around 5200 BC, the patriarchal Dnieper-Donets culture leaves the Mesolithic hunter-gatherer lifestyle and begins keeping cattle , sheep and goats . Other domestic animals kept included pigs , horses and dogs . Junglefowl were domesticated around c. 5500 BC in Southeast Asia. - The Zhaobaogou culture in China began c. 5400 BC. It

9856-747: The continent. A similar wet episode took place in the tropical Americas, China, Asia, India , the Makran region, the Middle East and the Arabian Peninsula and appears to relate to the same orbital forcing as the AHP. An early Holocene monsoonal episode extended as far as the Mojave Desert in North America. In contrast, a drier episode is recorded from much of South America where Lake Titicaca , Lake Junin ,

9984-714: The desert such as highlands like the Red Sea Hills were reached by the westerlies or weather systems associated with the subtropical jet stream —and thus received precipitation—is contentious. It is only clearly supported for the Maghreb in northwestern Africa and parts of northeastern Africa, though river flow / terrace formation and lake development in the Tibesti and Jebel Marra mountains and residual Nile flow may be explained in this way. The highlands of Africa appear to have been less affected by drought during

10112-590: The discharge of the Amazon River and water availability in the Atacama were lower. The discharge of the Congo , Niger , Nile , Ntem , Rufiji , and Sanaga rivers increased. Runoff from Algeria , equatorial Africa, northeastern Africa and the western Sahara was also larger. Changes in the morphology of the river systems and their alluvial plains occurred in response to the increased discharge, and

10240-473: The discovery of these rock paintings in now-inhospitable parts of the Sahara. When the period ended, humans gradually abandoned the desert in favour of regions with more secure water supplies, such as the Nile Valley and Mesopotamia , where they gave rise to early complex societies . Herodotus in 440 BC and Strabo in 23 AD discussed the existence of a greener Sahara, although their reports were at first questioned owing to their anecdotal nature. In 1850

10368-602: The earliest artifacts found in Central Asia derive from Siberia. Large scale constructions occur as early as 6000 BC. Prehistoric settlements in remote Siberia, Russia have revealed that 8,000 years ago construction of complex defensive structures, such as the Amnya complex , occurred with political warfare. They are the oldest fortresses in the world. Finding such ancient fortifications challenges previous understanding of early human societies. It suggests that agriculture wasn’t

10496-459: The eastern Sahara have been used as analogues for former river systems on Mars . Conditions and resources were ripe for first hunter-gatherers , fishermen and, later, pastoralists ; the exact chronology – when humans returned in the Sahara after the onset of the AHP – is disputed. They may have come either from the north ( Maghreb or Cyrenaica ) where the Capsian culture was located,

10624-610: The end of the global deglaciation which had followed the Last Glacial Maximum and caused sea levels to rise by some 60 m (200 ft) over a period of about 5,000 years. Neolithic culture and technology had spread from the Near East and into Eastern Europe by 6000 BC. Its development in the Far East grew apace and there is increasing evidence through the millennium of its presence in prehistoric Egypt and

10752-422: The equator, and rainforests had retreated in favour of afromontane and savannah landscapes as temperatures, rainfall, and humidity decreased. There is little and often equivocal evidence of human activity in the Sahara or Arabia at that time, reflecting its drier nature; in the Acacus Mountains the last human presence was recorded 70,000–61,000 years ago and by the LGM humans had largely retreated to

10880-504: The expansion of the population of other animals such as Hubert's multimammate mouse and Natal multimammate mouse . A number of lakes formed or expanded in the Sahara and the Hoggar and Tibesti Mountains . The largest of them was Lake Chad which increased to at least ten times its present-day size to form Lake Megachad. This enlarged Lake Chad reached dimensions of 1,000 by 600 kilometres (620 mi × 370 mi) in north–south and east–west direction respectively, covering

11008-510: The fertilizing effects of increased carbon dioxide concentrations in the atmosphere. Other sources of albedo changes: Warmer extratropics during summer may have drawn the Intertropical Convergence Zone (ITCZ) northward by about five or seven degrees latitude , resulting in precipitation changes. Sea surface temperatures off North Africa warmed under orbital effects and through weaker trade winds , leading to

11136-692: The first Paleo-Indians. They migrated into Alaska and northern Canada, south along the Pacific Coast, into the interior of Canada, and south to the Great Plains and the American Southwest. - Indo-European cultures descended from Ancient North Eurasians long ago, continue to expand Westwards from Central Russia . It provides linguistic evidence for the geographical location of these languages around that time, agreeing with archeological evidence that Indo-European speakers were present in

11264-597: The first places where pottery was developed probably under the influence of increased availability of resources during the AHP. The humid period also favoured its development and spread in West Africa during the 10th millennium BC ; the so-called "wavy line" or "dotted wavy-line" motif was widespread across Northern Africa and as far as Lake Turkana . 6th millennium BC ICS stages / ages (official) Blytt–Sernander stages/ages *Relative to year 2000 ( b2k ). The 6th millennium BC spanned

11392-584: The flow of water and sediment in the Nile. In the East African Rift water levels in lakes began to rise by about 15,500/15,000 -12,000 years ago; Lake Kivu began overflowing into Lake Tanganyika by about 10,500 years ago. About the same time that the AHP started, the cold glacial climate in Europe associated with Heinrich event 1 ended with climate changing as far as Australasia . A warming and retreat of sea ice around Antarctica coincides with

11520-473: The former being wetter than the latter. The African humid period was not the first such phase; evidence for about 230 older such "green Sahara"/wet periods exist going back perhaps to the first appearance of the Sahara 7–8 million years ago, for example during Marine Isotope Stage 5 a and c. Earlier humid periods appear to have been more intense than the AHP of the Holocene, including the exceptionally intense Eemian humid period. This humid period provided

11648-476: The lack of lakes (cattle having high requirements of drinking water ) may however have limited the occurrence of cattle. Animal husbandry picked up in earnest around 7,000 years ago when domestic animals came to the Sahara, and a population boom may be linked to this change in cultural practice; cattle and goats spread southwestwards from northeasternmost Africa from 8,000 years before present. Dairying has been demonstrated in some locations and cattle-husbandry

11776-529: The last glacial maximum. The end of the glacial drought occurred between 17,000 and 11,000 years ago, with an earlier beginning noted in the Acacus and Saharan mountains 26,500–22,500 and (possibly) 18,500 years ago, respectively. In southern and central Africa earlier starts 17,000 and 17,500 years ago, respectively, may be linked to Antarctic warming, while Lake Malawi appears to have been low until about 10,000 years ago. High lake levels occurred in

11904-542: The late Pleistocene and Holocene geologic epochs, when northern Africa was wetter than today. The covering of much of the Sahara desert by grasses, trees and lakes was caused by changes in the Earth's axial tilt ; changes in vegetation and dust in the Sahara which strengthened the African monsoon ; and increased greenhouse gases . During the preceding Last Glacial Maximum , the Sahara contained extensive dune fields and

12032-552: The late 7th millennium BC goats and sheep , apparently imported from Western Asia, appear. Many large hearths also appear. Early pottery from the Nabta Playa- Bir Kiseiba area has characteristics unlike pottery from surrounding regions. This is followed by pottery with characteristics found only in the Western Desert . Later pottery from c. 5500 BC (Al Jerar phase) has similarities with pottery from

12160-472: The late 7th millennium BC, originating from cattle domesticated in the Euphrates valley . Larger settlements began to appear at Nabta Playa by the 7th millennium BC , relying on deep wells for sources of water. Small huts were constructed in straight rows . Sustenance included wild plants, such as legumes , millets , sorghum , tubers , and fruit. Around 6800 BC they began to make pottery locally. In

12288-412: The magnitude and timing of the changes are unclear. Depending on how and where measurements and reconstructions are made, different beginning dates, ending dates, durations and precipitation levels have been determined for the African humid period. The amounts of precipitation reconstructed from paleoclimate records and simulated by climate modelling are often inconsistent with each other; in general,

12416-469: The main Nile may have been dammed by dunes. The Nile Delta was partially dry, with sandy plains extending between ephemeral channels and exposed seafloor, and it became a source of sand for ergs farther east. Other lakes across Africa, such as Lake Chad and Lake Tanganyika , also had shrunk during this time, and both the Niger River and Senegal River were stunted. Whether some parts of

12544-531: The monsoon is unclear. During summer, solar heating is stronger over the North African land than over the ocean, forming a low pressure area that draws moist air and precipitation in from the Atlantic Ocean. This effect was strengthened by the increased summer insolation, leading to a stronger monsoon that also reached farther north. The effects of these circulation changes reached as far as

12672-440: The most prominent alignments of megaliths labelled the "C-line", which they said aligned to the rising of Sirius circa 4820 BC. Brophy and Rosen stated in 2005 that megalith orientations and star positions reported by Wendorf and Malville were in error, noting that "Given these corrected data, we see that Sirius actually aligned with the C-line circa 6000 BC. We estimate that 6088 BC Sirius had a declination of −36.51 degrees, for

12800-485: The northward expansion of the monsoon. There is not universal agreement on the effects of dust on precipitation in the Sahel, however, in part because the effects of dust on precipitation may be dependent on its size. In addition to raw precipitation changes, changes in precipitation seasonality such as the length of dry seasons need to be considered when assessing the effects of climate change on vegetation, as well as

12928-604: The occurrence of submarine landslides in the area have been related to the activity of these rivers. Rivers such as the Irharhar in Algeria , Libya and Tunisia and the Sahabi and Kufra rivers in Libya were active during this time although there is some doubt that they had perennial flow; they appear to have been more important in earlier humid periods. Small watersheds, wadis and rivers discharging into endorheic basins such as Wadi Tanezzuft also carried water during

13056-493: The only driver for people to start building permanent settlements. - Large scale backwards migrations occur with Native American populations migrating back into Asia , settling in areas such as the Altai Mountains several times over a span of thousands of years, earliest dated to 5500 BC. This is potentially linked to the environmental changes at the time (see Mount Mazama ), which remained preserved in oral history of

13184-483: The onset of the AHP in tropical southeastern Africa; there, orbital changes would be expected to lead to climate variations opposite to those in the Northern Hemisphere. The pattern of humidity changes in south-eastern Africa are complex. The African humid period extended over most of Africa: The Sahara and eastern, southeastern and equatorial Africa. In general, forests and woodlands expanded through

13312-654: The onset of the African humid period as well as to increased humidity in Arabia. Later, in the Blytt–Sernander sequence the humid period coincides with the Atlantic period . During the Last Glacial Maximum , the Sahara and Sahel had been extremely dry with even less precipitation than today as reflected by the extent of dune sheets and water levels in closed lakes . The Sahara was much larger, extending 500–800 kilometres (310–500 mi) farther south to about 12° northern latitude. Dunes were active much closer to

13440-527: The original description was partly inaccurate, later widespread evidence for such orbital controls on climate was found. At first it was believed that humid periods in Africa correlate with glacial stages (" pluvial hypothesis ") before radiocarbon dating became widespread. The development and existence of the African humid period has been investigated with archaeology , climate modelling and paleoproxies , with archaeological sites , dunes and deposits left by lakes, aeolian deposits and leaf wax in

13568-576: The pathways for early humans to cross Arabia and Northern Africa and which, together with later moist periods, has been linked to expansions of the Aterian populations and the speciation of insect species. Such humid periods are usually associated with interglacials , while glacial stages correlate to dry periods; they occur during precession minima, unless large ice sheets or insufficient greenhouse gas concentrations suppress their onset. The Bølling–Allerød warming appears to be synchronous with

13696-631: The people who occupied this region at that time may have been early pastoralists , or like the Saami practiced semi-pastoralism. This is disputed by other sources as the cattle remains found at Nabta have been shown to be morphologically wild in several studies, and hunter-gatherers at the nearby Saharan site of Uan Afada in Libya were penning wild Barbary sheep , an animal that was never domesticated. According to Michael Brass (2018) early cattle remains from Nabta Playa were wild hunted aurochs , whilst domesticated cattle were introduced to northeast Africa in

13824-437: The perihelion at the time of summer solstice , increasing the amount of solar radiation by about 8%, resulting in the African monsoon becoming both stronger and reaching farther north. Between 15,000 and 5,000 years ago, summer insolation was at least 4% higher than today. The obliquity also decreased during the Holocene but the effect of obliquity changes on the climate is focused on the high latitudes and its influence on

13952-526: The researcher Heinrich Barth discussed the possibility of past climate change leading to increased wetness in the Sahara after discovering petroglyphs in the Murzuq Desert , as did Ahmed Hassanein following his 1923 exploration of the Libyan Desert when he saw depictions of savanna animals at Gabal El Uweinat . Further discoveries of petroglyphs led desert explorer László Almásy to coin

14080-553: The resulting caldera filled with water. Another major eruption occurred c. 5550 BC on Mount Takahe , Antarctica , possibly creating an ozone hole in the region. The carbon-14 content in tree rings created c. 5480 BC indicates an abnormal level of solar activity . The epoch of the Byzantine calendar , used in the Byzantine Empire and many Christian Orthodox countries, is equivalent to 1 September 5509 BC on

14208-452: The same epoch, circa 6270 BC. Brophy argues that the Calendar Circle correlation with Orion's belt occurred between 6400 BC and 4900 BC, matching radio-carbon dates of some campfires in the area. A 2007 article by a team of University of Colorado archaeoastronomers and archaeologists (Malville, Schild, Wendorf and Brenmer, three of whom had been involved in the original discovery of the site and its astronomical alignment) responded to

14336-462: The sea and wetlands playing an important role. Pollen , lake deposits and former levels of lakes have been used to study the ecosystems of the African humid period, and charcoal and leaf impressions have been used to identify vegetation changes. Questions in AHP research are its beginning, cause, intensity, end, land feedbacks and fluctuations during the AHP. The time 6,000 years ago has received particular attention, especially since that period of

14464-531: The sides and tops of dunes and may not represent an original set of aligned stele". They also criticised suggestions made by Brophy in his 2002 book The Origin Map that there was a representation of the Milky Way as it was in 17,500 BC and maps of Orion at 16,500 BC, saying "These extremely early dates as well as the proposition that the nomads had contact with extra-galactic aliens are inconsistent with

14592-499: The simulation of the Green Sahara is considered a problem for earth system models. There is more evidence of the late phase of the AHP than its beginning. Erosion of lake sediments and carbon reservoir effects make it difficult to date when they dried up. Vegetation changes by themselves do not necessarily indicate precipitation changes, as changes in seasonality, plant species composition and changes in land use also play

14720-751: The south ( Sub-Saharan Africa ), or the east ( Nile Valley ). The human population in the Sahara rapidly increased during the AHP, interrupted by a brief decline between 7,600 and 6,700 years ago. Traces of human activity have been found in the Acacus Mountains where caves and rock shelters were used as basecamps for humans, such as the Uan Afuda cave and the Uan Tabu and Takarkori rock shelters. The first occupation in Takarkori took place between 10,000 and 9,000 years ago; about five millennia of human cultural evolution are recorded there. At Gobero in

14848-605: The south by the Chari - Logone and Komadugu Rivers . The Chari River was the main tributary while the rivers draining the Tibesti formed alluvial fans /the Angamma river delta at their entry into northern Lake Chad. Skeletons of elephants, hippos and hominins have been found in the Angamma delta, which is the dominant shoreline feature of northern Lake Chad. The lake overflowed into the Niger River during highstand through

14976-400: The southerly line of three stones inside the Calendar Circle represented the three stars of Orion’s Belt and the other three stones inside the calendar circle represented the shoulders and head stars of Orion as they appeared in the sky. These correspondences were for two dates – circa 4800 BC and at precessional opposition – representing how the sky "moves" long term. Brophy proposes that

15104-505: The start of the African humid period, although the Antarctic Cold Reversal also falls into this time and may relate to a drought interval recorded in the Gulf of Guinea . The African humid period was caused by a stronger West African Monsoon directed by changes in solar irradiance and in albedo feedbacks. These led to increased moisture import from both the equatorial Atlantic into West Africa, as well as from

15232-486: The subtropics. Obliquity and precession are responsible for two of the foremost Milankovich cycles and are responsible not only for the onset and cessation of ice ages but also for monsoon strength variations. Southern Hemisphere monsoons are expected to have the opposite response of Northern Hemisphere monsoons to precession, as the insolation changes are reversed; this observation is borne out by data from South America. The precession change increased seasonality in

15360-504: The vegetation changed; in the desert the expansion of vegetation facilitated fire activity, while in the savanna the increased prevalence of woody vegetation reduced fire activity. Forests and plants from the humid tropics were concentrated around lakes, rivers and the Atlantic Ocean coast of Senegal ; waterbodies were also settled by aquatic and partially aquatic plants and the Senegalese coast by mangroves . The landscape during

15488-466: The vegetation. Reduced dust generation from a wetter Sahara, where major dust-generating regions were submerged by lakes, influences the climate by reducing the amount of light absorbed by dust. Decreased dust emissions also modify cloud properties, making them less reflective and more efficient at inducing precipitation. In climate models, reduced amounts of dust in the troposphere together with vegetation changes can often but not always explain

15616-540: The western and central sectors and the Libyan sand sea was still a desert although pure desert areas retreated or became arid / semiarid . An arid belt may have existed north of 22° latitude and towards the Nile Delta, or the vegetation and the African monsoon might have reached 28–31° northern latitude; in general conditions between 21° and 28° northern latitude are poorly known. Dry areas may have persisted in

15744-480: The work of Brophy and Rosen, in particular their claims for an alignment with Sirius in 6088 BC and other alignments which they dated to 6270 BC, saying that these dates "are about 1500 years earlier than our best estimates for the Terminal Neolithic and the construction of megalithic structures" at Nabta Playa. The Sirius alignment in question was originally proposed by Wendorf and Malville, for one of

15872-463: The years 6000 BC to 5001 BC (c. 8 ka to c. 7 ka). It is impossible to precisely date events that happened around the time of this millennium and all dates mentioned here are estimates mostly based on geological and anthropological analysis. The only exceptions are the felling dates for some construction timbers from Neolithic wells in Central Europe . This millennium is reckoned to mark

16000-405: Was delayed by the increased food availability during the AHP, it only took place around 2,500 BC . Humans created rock art such as petroglyphs and rock paintings in the Sahara, perhaps the largest density of such creations in the world. Scenes include animals and everyday life such as swimming which supports the presence of past wetter climates. One well-known such petroglyph location

16128-506: Was in part triggered by a stronger West African and Indian monsoon, perhaps explaining why the effects of the AHP extended into the Southern Hemisphere. The behaviour of the easterly trade winds is unclear; increased moisture transport by easterly trade winds may have aided in the development of the AHP but alternatively a stronger Indian Monsoon that draws easterly winds away from East Africa may have occurred. Changes in

16256-647: Was in the north-eastern part of the country, primarily in the Luan River valley in Inner Mongolia and northern Hebei . - The ' Yangshao culture (仰韶文化, pinyin: Yǎngsháo wénhuà) was a Neolithic culture that existed extensively along the middle reaches of the Yellow River in China from around the end of this millennium, from 5000 BC to 3000 BC. Excavations found that children were buried in painted pottery jars. Pottery style emerging from

16384-517: Was mostly uninhabited. It was much larger than today, and its lakes and rivers such as Lake Victoria and the White Nile were either dry or at low levels. The humid period began about 14,600–14,500 years ago at the end of Heinrich event 1 , simultaneously to the Bølling–Allerød warming . Rivers and lakes such as Lake Chad formed or expanded, glaciers grew on Mount Kilimanjaro and the Sahara retreated. Two major dry fluctuations occurred; during

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