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86-529: Dhar Tichitt is one of the oldest known archaeological occupation sites in West Africa. About 500 settlements littered the region in the former savannah of the Sahara. In addition to herding livestock (cattle, sheep, goats), its inhabitants hunted, fished, collected wild grain, and grew bulrush millet . The inhabitants and creators of these settlements during these periods are thought to have been ancestors of

172-503: A rock surface by incising, picking, carving, or abrading , as a form of rock art . Outside North America , scholars often use terms such as "carving", "engraving", or other descriptions of the technique to refer to such images. Petroglyphs, estimated to be 20,000 years old are classified as protected monuments and have been added to the tentative list of UNESCO 's World Heritage Sites . Petroglyphs are found worldwide, and are often associated with prehistoric peoples. The word comes from

258-438: A continuous tree canopy which would prevent further grass growth. Prior to European settlement aboriginal land use practices, including fire, influenced vegetation and may have maintained and modified savanna flora. It has been suggested by many authors that aboriginal burning created a structurally more open savanna landscape. Aboriginal burning certainly created a habitat mosaic that probably increased biodiversity and changed

344-491: A dramatic reduction in basal area and canopy cover, often leaves a high percentage of woody plants alive either as seedlings too small to be affected or as plants capable of re-sprouting from lignotubers and broken stumps. A population of woody plants equal to half or more of the original number often remains following pulling of eucalypt communities, even if all the trees over 5 metres are uprooted completely. A number of exotic plants species have been introduced to savannas around

430-428: A dry season and a shorter rainy season. These humid phases would have made it possible for moisture to accumulate in the sandy flats, leading to small lakes forming in the interdunal depressions of the region. Around 2,500 BP, as the climate began to change into an increasing pattern of desertification , it is thought that people were forced out of the region. The site was first extensively excavated by Patrick Munson in

516-804: A high tree density. It is often believed that savannas feature widely spaced, scattered trees. However, in many savannas, tree densities are higher and trees are more regularly spaced than in forests. The South American savanna types cerrado sensu stricto and cerrado dense typically have densities of trees similar to or higher than that found in South American tropical forests, with savanna ranging from 800 to 3300 trees per hectare (trees/ha) and adjacent forests with 800–2000 trees/ha. Similarly Guinean savanna has 129 trees/ha, compared to 103 for riparian forest , while Eastern Australian sclerophyll forests have average tree densities of approximately 100 per hectare , comparable to savannas in

602-692: A landform or the surrounding terrain, such as rivers and other geographic features. Some petroglyph maps, depicting trails, as well as containing symbols communicating the time and distances travelled along those trails, exist; other petroglyph maps act as astronomical markers. As well as holding geographic and astronomical importance, other petroglyphs may also have been a by-product of various rituals: sites in India, for example, have seen some petroglyphs identified as musical instruments or " rock gongs ". Some petroglyphs likely formed types of symbolic communication, such as types of proto-writing . Later glyphs from

688-414: A limited amount of botanical evidence was also found. The majority of this data was gathered from the impressions of grain left behind on ceramic potsherds, although some remains of seeds and grains were also present at the sites. Of the half dozen species of plants found at the site, Pennisetum or bulrush millet was the only domesticate found. Some wild grains and fruits also represent a small amount of

774-438: A major departure from the previous phases, since the sites contain precise stone-masonry constructions which measured 20 to 40 meters in diameter. These compounds appear to have been walled and fortified. Although the ceramic culture remained constant in this period, there was a change with the newfound presence of large amounts of non-portable milling stones. The Chebka period had the same level of architectural complexity, with

860-402: A means of clearing land. In the 1950s arboricides suitable for stem injection were developed. War-surplus heavy machinery was made available, and these were used for either pushing timber, or for pulling using a chain and ball strung between two machines. These two new methods of timber control, along with the introduction and widespread adoption of several new pasture grasses and legumes promoted

946-444: A reduction in the need to burn to produce a flush of green growth because legumes retain high nutrient levels throughout the year, and because fires can have a negative impact on legume populations which causes a reluctance to burn. The closed forest types such as broadleaf forests and rainforests are usually not grazed owing to the closed structure precluding grass growth, and hence offering little opportunity for grazing. In contrast

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1032-404: A reliable basis. Thus, people begun settling down in communities adjacent to isolated pockets of moisture ( oases ) and practicing agriculture. At the same time, some interpretations have concluded that during the dry season, wild grains and fruits were collected in the lowlands to supplement the otherwise pastoralist diet . Thus, there is evidence for variance in diet during different seasons, with

1118-576: A result of decisions "enforced for the benefit of the community as a whole." Dhar Tichitt and the surrounding areas are characterized by steep sandstone cliffs (the word dhar meaning escarpment in Hassaniya Arabic , sandy flats with scattered clumps of coarse grasses, and interdunal depressions. Today, the climate of the Dhar Tichitt region today is arid and hot, with it only experiencing about 100 millimeters of rain per year. However, in

1204-438: A result of global climate change, particularly at ecotones such as savannas so often represent. A savanna can simply be distinguished by the open savanna, where grass prevails and trees are rare; and the wooded savanna, where the trees are densest, bordering an open woodland or forest. Specific savanna ecoregions of several different types include: Petroglyph A petroglyph is an image created by removing part of

1290-469: A resurgence in tree clearing. The 1980s also saw the release of soil-applied arboricides, notably tebuthiuron , that could be utilised without cutting and injecting each individual tree. In many ways "artificial" clearing, particularly pulling, mimics the effects of fire and, in savannas adapted to regeneration after fire as most Queensland savannas are, there is a similar response to that after fire. Tree clearing in many savanna communities, although causing

1376-402: A ritualistically important center given its unproportionally large number of tumuli that is not seen in any other sites within the associated Tichitt culture. Interestingly, the large stone walls at the Dhar Tichitt site appear to be designed for spatial division, rather than defensive walls for outside attackers. Some experts have speculated that Dhar Tichitt's unique system of social organization

1462-459: A simplified yet widespread climatic concept. The divergence has sometimes caused areas such as extensive savannas north and south of the Congo and Amazon Rivers to be excluded from mapped savanna categories. In different parts of North America, the word "savanna" has been used interchangeably with " barrens ", " prairie ", " glade ", "grassland" and " oak opening ". Different authors have defined

1548-851: A temporary rock shelter were noticed adjacent to a Murugan temple which is in ruins on top of the Kothaiyurumbu hill. During recent years a large number of rock carvings has been identified in different parts of Iran. The vast majority depict the ibex . Rock drawings were found in December 2016 near Golpayegan , Iran , which may be the oldest drawings discovered, with one cluster possibly 40,000 years old. Accurate estimations were unavailable due to US sanctions. The oldest pictographs in Iran are seen in Yafteh cave in Lorestan that date back 40,000 and

1634-474: Is able to represent an accurate chronology. Overall, the chronology at the site is contentious, especially due to the spatial separation across a large space which makes it difficult to determine relative stratigraphy . The first evidence for domestication of grain in the Dhar Tichitt region came from impressions in of grain on potsherds found by Patrick Munson's excavation. These impressions demonstrated that millet ( Pennisetum glaucum ) had been domesticated in

1720-771: Is harder to explain the common styles. This could be mere coincidence, an indication that certain groups of people migrated widely from some initial common area, or indication of a common origin. In 1853, George Tate presented a paper to the Berwick Naturalists' Club, at which a John Collingwood Bruce agreed that the carvings had "... a common origin, and indicate a symbolic meaning, representing some popular thought." In his cataloguing of Scottish rock art, Ronald Morris summarized 104 different theories on their interpretation. Other theories suggest that petroglyphs were carved by spiritual leaders, such as shamans , in an altered state of consciousness , perhaps induced by

1806-564: Is indicative of a heterarchical organization system as seen in Jenné-jeno. Moreover, the increased the diversity in decoration and pottery types as the culture transitioned into Dhar Tichitt may have been related to specialization. Many archeologists have hypothesized a connection between the Dhar Tichitt and the overarching Middle Niger River Delta cultures such as the Ghana Empire . Both archeological and linguistic evidence shows that

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1892-402: Is known to have occurred only at certain places within the site, such as Dakhlet el Atrouss I. The overall settlement at Dhar Tichitt can be divided into four distinct tiers including hamlets (2 ha), villages (less than 10 ha), district centers (15 ha), and regional centers (80 ha). It is thought that each of these district centers was capable of managing up to 20 different hamlets. For most of

1978-483: Is not prominent but that rivers in savanna landscapes erode more by lateral migration . Flooding and associated sheet wash have been proposed as dominant erosion processes in savanna plains. The savannas of tropical America comprise broadleaved trees such as Curatella , Byrsonima , and Bowdichia , with grasses such as Leersia and Paspalum . Bean relative Prosopis is common in the Argentinian savannas. In

2064-473: Is possible for there to be multiple stable biomes. The annual rainfall ranges from 500 mm (19.69 in) to 1,270 mm (50.00 in) per year, with the precipitation being more common in six or eight months of the year, followed by a period of drought. Savannas may at times be classified as forests. In climatic geomorphology it has been noted that many savannas occur in areas of pediplains and inselbergs . It has been posited that river incision

2150-419: Is vague and therefore the two can be combined into a single biome as both woodlands and savannas feature open-canopied trees with crowns not usually interlinking (mostly forming 25-60% cover). Over many large tropical areas, the dominant biome (forest, savanna or grassland) can not be predicted only by the climate, as historical events plays also a key role, for example, fire activity. In some areas, indeed, it

2236-411: Is very limited evidence for imported materials into the region, which some have taken to be proof that there was a long-distance trading network that was only accessible to the elites of the society. However, it was also suggested that such scarce evidence could not be used to make conclusions about how the socioeconomic system of Tichitt was organized. Several factors point to the idea that households at

2322-645: The Greek prefix petro- , from πέτρα petra meaning " stone ", and γλύφω glýphō meaning "carve", and was originally coined in French as pétroglyphe . In scholarly texts, a petroglyph is a rock engraving, whereas a petrograph (or pictograph ) is a rock painting. In common usage, the words are sometimes used interchangeably. Both types of image belong to the wider and more general category of rock art or parietal art . Petroforms , or patterns and shapes made by many large rocks and boulders over

2408-462: The Mediterranean region were likewise created and maintained by anthropogenic fire. Intentional controlled burns typically create fires confined to the herbaceous layer that do little long term damage to mature trees. This prevents more catastrophic wildfires that could do much more damage. However, these fires either kill or suppress tree seedlings, thus preventing the establishment of

2494-645: The Nordic Bronze Age in Scandinavia seem to refer to some form of territorial boundary between tribes , in addition to holding possible religious meanings. Petroglyph styles have been recognised as having local or regional "dialects" from similar or neighboring peoples. Siberian inscriptions loosely resemble an early form of runes , although no direct relationship has been established. Petroglyphs from different continents show similarities. While people would be inspired by their direct surroundings, it

2580-492: The Soninke people . Plateau settlements consisted of multiple drystone-compounds containing houses and granaries (or "storage facilities"), sometimes with "street" layouts, which were constructed between c. 1400 BCE and 300 BCE. Large livestock enclosures were erected in proximity of some sites. And around some settlements, larger common stone "circumvallation walls" were built, suggesting that "special purpose groups" cooperated as

2666-476: The greenhouse effect may result in an alteration of the structure and function of savannas. Some authors have suggested that savannas and grasslands may become even more susceptible to woody plant encroachment as a result of greenhouse induced climate change . However, a recent case described a savanna increasing its range at the expense of forest in response to climate variation, and potential exists for similar rapid, dramatic shifts in vegetation distribution as

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2752-402: The millet forming a staple crop that was cultivated during the wet season while other wild sources of food that grew relatively well on sandy soils providing a supplementary food reservoir. Since the 1990s, research on the potsherd impressions has become more thorough. More recent dating using accelerated mass spectrometry has resulted in a newly calculated date of around 1900 to 1700 BCE for

2838-749: The prairies in North America and steppes in Eurasia , which feature cold winters, savannas are mostly located in areas having warm to hot climates, such as in Africa, Australia, Thailand, South America and India. The word derives from the Spanish sabana , which is itself a loanword from Taíno , which means "treeless grassland" in the West Indies . The letter b in Spanish, when positioned in

2924-517: The Akreijit deposit, his excavation discovered various microliths of diverse size and purpose, scrapers , projectile points , quartz pebbles and cores, milling stones , and a particular ceramic pottery culture. The Khimiya phase yielded a larger amount of pottery, although a significant portion of it was of the same variety as the Akreijit layer. The most notable contents of the Khimiya phase were

3010-554: The Australian savanna, mammals in the family Macropodidae predominate, such as kangaroos and wallabies, though cattle, horses, camels, donkeys and the Asian water buffalo , among others, have been introduced by humans. It is estimated that less than three percent of savanna ecosystems can be classified as highly intact. Reasons for savanna degradation are manifold, as outlined below. Savannas are subject to regular wildfires and

3096-632: The Berbers arrived in the first millennium BCE on the basis of local rock art . Violent conflicts with Berbers may have contributed to the fall of this society. Moreover, the Berber influences may be present in the material culture of the Late Tichitt period. Sites such as Dhar Nema show the sudden presence of metallurgy, which were not associated with any of the previous Tichitt culture sites. Some suggest Berbers may have brought metal-making culture into

3182-497: The Classical compound clusters, large areas outside of the walled compounds were adjacent to the living quarters that are thought to have been used for maintaining livestock or gardens. Research on the funerary tumuli of the site has been limited thus far, but experts believe that the larger presence of tumuli at this site indicates the possibility of it being an important cultural site. It is also possible that Dhar Tichitt represents

3268-492: The Dhar Tichitt region was inhabited by pastoralists around 4500 BP, and it likely reached its population and cultural peak during this period. He also believed that the 4500 to 4000 BP date range of most significant occupation corresponded well with the Mid-Holocene humid period . Munson's original interpretation with eight distinct phases was thoroughly refuted and reformatted by later archaeologists after more analysis of

3354-505: The East African savannas, Acacia , Combretum , baobabs , Borassus , and Euphorbia are a common vegetation genera. Drier savannas there feature spiny shrubs and grasses, such as Andropogon , Hyparrhenia , and Themeda . Wetter savannas include Brachystegia trees and Pennisetum purpureum , and elephant grass type. West African savanna trees include Anogeissus , Combretum , and Strychnos . Indian savannas are mostly cleared, but

3440-527: The Northern Territory, Australia savanna, and 480,000 ha of savanna were being cleared annually in Queensland in the 2000s, primarily to improve pasture production. Substantial savanna areas have been cleared of woody vegetation and much of the area that remains today is vegetation that has been disturbed by either clearing or thinning at some point in the past. Clearing is carried out by

3526-592: The Pre-Tichitt period as being characterized by mobile pastoralists and a complete lack of agricultural developments . Despite the lack of evidence for cereal domestication during this period, it is now thought that pastoralism was likely practiced at the same time as millet agriculture for a significant period of time prior to the Early Tichitt period. Some interpretations suggest that as the Tichitt culture

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3612-654: The Soninke people associated with the Ghana Empire are descendants of the remnants of the Tichitt culture following its collapse. Most of the archeological evidence has come in the form of ceramics, cattle remains, and stonework present on the Northern border of the known Middle Niger boundaries. The earliest Tichitt assemblages present in this region have been dated to around 1300 BCE at the Saberi Faita site. Thus,

3698-676: The Witwatersrand studies present-day links between religion and rock art among the San people of the Kalahari Desert . Though the San people's artworks are predominantly paintings, the beliefs behind them can perhaps be used as a basis for understanding other types of rock art, including petroglyphs. To quote from the RARI website: Using knowledge of San beliefs, researchers have shown that

3784-476: The architecture, ceramics, rock engravings , lithics, and possible economies at the site. In the field seasons of 1980 and 1981, a large number of animal bone fragments and samples were found. These included domesticated animals such as cows, sheep, goats, and camels as well as a wide variety of wild animals ranging from aquatic animals like hippopotami to desert antelope like the Addax . Between 1980 and 1983,

3870-686: The art played a fundamental part in the religious lives of its painters. The art captured things from the San's world behind the rock-face: the other world inhabited by spirit creatures, to which dancers could travel in animal form, and where people of ecstasy could draw power and bring it back for healing, rain-making and capturing the game. Tunisia Eight sites in Hong Kong : Kethaiyurumpu, Tamil Nadu. Situated 28 km north west of Dindigal, Tamil Nadu nearby Idaiyakottai and six km south west of Oddanchartam has revealed several petroglyphs mostly represent abstract symbols on two rocks, which looks like

3956-429: The botanical evidence present at the site. Carnelian and amazonite beads, as well as stone-arm rings and axes have been found in association with the site, and these objects are known to represent at least some level of long-distance trade . Further excavations of the earliest layer of desposition yielded eight ostrich eggshell beads and a pierced bone disc. Only one fragment of an iron slag has been discovered from

4042-415: The court of the cacique Carlos in present-day Panama . The accounts are inexact, but this is usually placed in present-day Madugandí or at points on the nearby Guna Yala coast opposite Ustupo or on Point Mosquitos . These areas are now either given over to modern cropland or jungle . Many grassy landscapes and mixed communities of trees, shrubs, and grasses were described as savanna before

4128-510: The culture's potential funerary perspectives. Furthermore, new excavations have taken time to reconstruct the climactic changes which resulted in the demise of this population center. This site is considered a Neolithic site. The Neolithic period in Africa (sometimes referred to as the Pastoral Neolithic ) is marked by a change from hunter-gatherer lifestyles towards agricultural or pastoralist ones. Patrick Munson hypothesized that

4214-446: The domestication of millet, which aligns the emergence of agriculture with the Early Tichitt period. Interestingly, the Tichitt culture was not unique in its domestication of millet, with some estimates placing domestication in associated Sahelian regions at around 2500 to 2000 BCE. In fact, it has been suggested that domestication was taking place as early as the fourth millennium BCE. It is likely that grain domestication in Dhar Tichitt

4300-566: The ecosystem appears to be the result of human use of fire. For example, Native Americans created the Pre-Columbian woodlands of North America by periodically burning where fire-resistant plants were the dominant species. Aboriginal burning appears to have been responsible for the widespread occurrence of savanna in tropical Australia and New Guinea , and savannas in India are a result of human fire use. The maquis shrub savannas of

4386-467: The establishment, growth and survival of plant species and in turn can lead to a change in woodland structure and composition. That being said, impact of grazing animals can be reduced. Looking at Elephant impact on Savannas, the overall impact is reduced in the presence of rainfall and fences. Large areas of Australian and South American savannas have been cleared of trees, and this clearing continues today. For example, land clearing and fracking threaten

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4472-483: The grazing industry in an attempt to increase the quality and quantity of feed available for stock and to improve the management of livestock. The removal of trees from savanna land removes the competition for water from the grasses present, and can lead to a two to fourfold increase in pasture production, as well as improving the quality of the feed available. Since stock carrying capacity is strongly correlated with herbage yield, there can be major financial benefits from

4558-587: The ground, are also quite different. Inuksuit are not petroglyphs, but human-made rock forms found in Arctic regions. Petroglyphs have been found in all parts of the globe except Antarctica , with highest concentrations in parts of Africa, Scandinavia and Siberia, many examples of petroglyphs found globally are dated to approximately the Neolithic and late Upper Paleolithic boundary (roughly 10,000 to 12,000 years ago). Around 7,000 to 9,000 years ago, following

4644-413: The huge number of fish and shellfish remains, as well as other aquatic cultures; this deposit indicated that the people of this time were extensively using the lakes in the region. The Goungou layer yielded largely similar pottery and lithic culture to that of the Khimiya, while the N'Khall only contained a small amount of unique lipped jars in a different stratigraphical layer. The Naghez layer showcases

4730-459: The introduction of a number of precursors of writing systems , the existence and creation of petroglyphs began to suffer and tail off, with different forms of art, such as pictographs and ideograms , taking their place. However, petroglyphs continued to be created and remained somewhat common, with various cultures continuing to use them for differing lengths of time, including cultures who continued to create them until contact with Western culture

4816-516: The late 1960s, with him publishing a detailed description of the sites in 1971. Munson determined an archeological sequence which he deemed to have existed entirely during the Neolithic period. He divided the site into eight discreet temporal phases based on the artifacts, architecture, and locations in the area. These periods were named, in chronological order, as follows: Akreijit, Khimiya, Goungou, N'Khall, Naghez, Chebka, Arriane, and Akjinjeir. In

4902-568: The lower limits of savanna tree coverage as 5–10% and upper limits range as 25–80% of an area. Two factors common to all savanna environments are rainfall variations from year to year, and dry season wildfires . In the Americas , e.g. in Belize , Central America , savanna vegetation is similar from Mexico to South America and to the Caribbean . The distinction between woodland and savanna

4988-400: The major sites related to Dhar Tichitt had been thoroughly excavated during the 1980s. Later efforts in the 1990s and 2000s were much more focused on analyzing lithics and pottery, as well as formulating hypotheses for the socioeconomic strategies of the inhabitants. Significant progress has taken place in research necropolises and tumuli located in and around these sites in order to decipher

5074-465: The middle of a word, is pronounced almost like an English v; hence the change of grapheme when transcribed into English. The word originally entered English as the Zauana in a description of the ilands of the kinges of Spayne from 1555. This was equivalent in the orthography of the times to zavana (see history of V ). Peter Martyr reported it as the local name for the plain around Comagre,

5160-425: The middle of the 19th century, when the concept of a tropical savanna climate became established. The Köppen climate classification system was strongly influenced by effects of temperature and precipitation upon tree growth, and oversimplified assumptions resulted in a tropical savanna classification concept which considered it as a "climatic climax" formation. The common usage to describe vegetation now conflicts with

5246-467: The oldest petroglyph discovered belongs to Timareh dating back to 40,800 years ago. Iran provides demonstrations of script formation from pictogram, ideogram, linear (2300 BC) or proto Elamite, geometric old Elamite script, Pahlevi script, Arabic script (906 years ago), Kufi script, and Farsi script back to at least 250 years ago. More than 50000 petroglyphs have been discovered, extended over all Iran's states. The oldest reliably dated rock art in

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5332-587: The only major difference being the placement of the sites. Interestingly, the Chebka and later sites did not appear to contain any evidence for aquatic fauna, which may point to the advancement of desertification. The last two periods, Arriane and Akjinjeir, are characterized by their much smaller and more compact sites. Both the Arriane and Akjinjeir phases still appeared to have some level of walls, albeit no real fortifications. The lithic and ceramic cultures found at

5418-469: The open structure of savannas allows the growth of a herbaceous layer and is commonly used for grazing domestic livestock. As a result, much of the world's savannas have undergone change as a result of grazing by sheep, goats and cattle, ranging from changes in pasture composition to woody plant encroachment . The removal of grass by grazing affects the woody plant component of woodland systems in two major ways. Grasses compete with woody plants for water in

5504-589: The past the area was much more temperate. Paleoclimatic data shows that there were three separate phases of significant humidity occurring during the Holocene period, one from 10,000 to 7,000 BP, another from 5,000 to 3,000 BP, and a more subtle episode at around 2,000 BP. During the middle humid phase, referred to in Mauritania as the Nouakchottian, the region experienced two different seasons per year,

5590-438: The potential to significantly alter the structure and composition of savannas worldwide, and have already done so in many areas through a number of processes including altering the fire regime, increasing grazing pressure, competing with native vegetation and occupying previously vacant ecological niches. Other plant species include: white sage, spotted cactus, cotton seed, rosemary. Human induced climate change resulting from

5676-507: The presence archeological evidence seems to point to the Tichitt diaspora as being directly related to the later emergence of Middle Niger cultures in the first millennium BCE. Both the change in climate (desertification of the Sahel) and influence of nomadic groups such as the Berbers are seen as plausible causes for the collapse of the Tichitt culture. Munson formulated the hypothesis that

5762-399: The recovered materials. Following analysis by Holl, Amblard, and MacDonald the chronology of the site were reorganized as follows: The majority of expert on this site agree with dividing the chronology into either three or four periods. However, there is some level of pushback from one of the leading archaeologists at the site, Sylvie Amblard-Pison, who does not believe that the current data

5848-471: The region, but also state that, "the major difficulty for testing this hypothesis is that so little is known about Berber metallurgy, its technology and its antiquity." Berbers are thought to have displaced many of the original inhabitants of the area, who then gradually moved into the northern Middle Niger River Valley. Savannah A savanna or savannah is a mixed woodland - grassland (i.e. grassy woodland) biome and ecosystem characterised by

5934-426: The region. Further analysis has demonstrated that the crop had been fully domesticated by at least 1100 BCE, but it likely occurred significantly before this. The original investigation put forth by Munson hypothesized that the people associated with this site had likely become sedentary as a result of decreasing rain over the period of hundreds of year. Due to the lack of water, wild grains could no longer be gathered on

6020-431: The removal of trees, such as assisting with grazing management: regions of dense tree and shrub cover harbors predators, leading to increased stock losses, for example, while woody plant cover hinders mustering in both sheep and cattle areas. A number of techniques have been employed to clear or kill woody plants in savannas. Early pastoralists used felling and girdling , the removal of a ring of bark and sapwood , as

6106-585: The reserved ones feature Acacia, Mimosa , and Zizyphus over a grass cover comprising Sehima and Dichanthium . The Australian savanna is abundant with sclerophyllous evergreen vegetation, which include the eucalyptus , as well as Acacia, Bauhinia , Pandanus with grasses such as Heteropogon and kangaroo grass (Themeda). Animals in the African savanna generally include the giraffe, elephant, buffalo, zebra, gnu, hippopotamus, rhinoceros, and antelope, where they rely on grass and/or tree foliage to survive. In

6192-453: The same region. Savannas are also characterised by seasonal water availability, with the majority of rainfall confined to one season. They are associated with several types of biomes , and are frequently in a transitional zone between forest and desert or grassland , though mostly a transition between desert to forest. Savanna covers approximately 20% of the Earth's land area. Unlike

6278-455: The site and was dated to the Late Tichitt period, possibly indicating the presence of metallurgy in the latter part of this site's habitation. In 1980, the first aerial survey of the site was performed via low altitude photographic coverage . This method allowed archaeologists to collect data regarding the placement of the stone structures in relation to each other by studying site morphology as well as topographical location. Essentially all of

6364-610: The site had socioeconomic differentiation . The massive stone compounds that have come to define the site in the Classical Tichitt period are known to have served as dividers for social space. Different spaces within these compounds housed different classes of workers. The settlements also appear to show the presence of multi-tiered hierarchies . The household compound units were characterized by different types of grinding stones that were likely used for different facets of food processing and tool-making. Not every dwelling unit

6450-508: The site were much less diverse and not aesthetically-driven as some of the previously dated artifacts were. Throughout the late 1970s and early 1980s, various archaeological expeditions took place to thoroughly excavate and document the Dhar Tichitt site, with most of these efforts largely focused on sites with stone architecture that were associated with the peak of the architecture. Studies led by archaeologists, many of them French, such as Hugot, Delneuf, Beyries, Amblard, Holl, and Roux explored

6536-515: The soil caused by the hooves of animals and through the erosion effects caused by the removal of protective plant cover. Such effects are most likely to occur on land subjected to repeated and heavy grazing. The effects of overstocking are often worst on soils of low fertility and in low rainfall areas below 500 mm, as most soil nutrients in these areas tend to be concentrated in the surface so any movement of soils can lead to severe degradation. Alteration in soil structure and nutrient levels affects

6622-606: The spread of weeds in savannas by the removal or reduction of the plants which would normally compete with potential weeds and hinder establishment. In addition to this, cattle and horses are implicated in the spread of the seeds of weed species such as prickly acacia ( Acacia nilotica ) and stylo ( Stylosanthes species). Alterations in savanna species composition brought about by grazing can alter ecosystem function, and are exacerbated by overgrazing and poor land management practices. Introduced grazing animals can also affect soil condition through physical compaction and break-up of

6708-519: The structure of woodlands and geographic range of numerous woodland species. It has been suggested by many authors that with the removal or alteration of traditional burning regimes many savannas are being replaced by forest and shrub thickets with little herbaceous layer. The consumption of herbage by introduced grazers in savanna woodlands has led to a reduction in the amount of fuel available for burning and resulted in fewer and cooler fires. The introduction of exotic pasture legumes has also led to

6794-463: The topsoil and removal by grazing reduces this competitive effect, potentially boosting tree growth. In addition to this effect, the removal of fuel reduces both the intensity and the frequency of fires which may control woody plant species. Grazing animals can have a more direct effect on woody plants by the browsing of palatable woody species. There is evidence that unpalatable woody plants have increased under grazing in savannas. Grazing also promotes

6880-506: The trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of grasses. Four savanna forms exist; savanna woodland where trees and shrubs form a light canopy, tree savanna with scattered trees and shrubs, shrub savanna with distributed shrubs, and grass savanna where trees and shrubs are mostly nonexistent. Savannas maintain an open canopy despite

6966-461: The use of natural hallucinogens . Many of the geometric patterns (known as form constants ) which recur in petroglyphs and cave paintings have been shown by David Lewis-Williams to be hardwired into the human brain. They frequently occur in visual disturbances and hallucinations brought on by drugs, migraine , and other stimuli. The Rock Art Research Institute (RARI) of the University of

7052-665: The world. Amongst the woody plant species are serious environmental weeds such as Prickly Acacia ( Acacia nilotica ), Rubbervine ( Cryptostegia grandiflora ), Mesquite ( Prosopis spp.), Lantana ( Lantana camara and L. montevidensis ) and Prickly Pear ( Opuntia spp.). A range of herbaceous species have also been introduced to these woodlands, either deliberately or accidentally including Rhodes grass and other Chloris species, Buffel grass ( Cenchrus ciliaris ), Giant rat's tail grass ( Sporobolus pyramidalis ) parthenium ( Parthenium hysterophorus ) and stylos ( Stylosanthes spp.) and other legumes . These introductions have

7138-503: Was arriving en-masse into the region that is now Southeastern Mauritania, they had already formed a concrete culture characterized by agro-pastoralism. Many of the societies of the Sahelian West Africa region are defined by organization into compounds, which encompass a given kinship group's material possessions. The presence and roles of elites in the Dhar Tichitt has been a point of much debate amongst archeologists. There

7224-400: Was equipped with the exact same set of grinding stones, which likely points to the fact that different households were focused on different types of production. Furthermore, each household appears to have contained at least one male and one female member, with many of the compounds probably having a large family unit suitable for their agro-pastoralist lifestyle. The clustering of funerary tumuli

7310-485: Was made in the 19th and 20th centuries. Many hypotheses exist as to the purpose of petroglyphs, depending on their location, age, and subject matter. Some petroglyph images most likely held a deep cultural and religious significance for the societies that created them. Many petroglyphs are thought to represent a type of symbolic or ritualistic language or communication style that remains not fully understood. Others, such as geocontourglyphs , more clearly depict or represent

7396-551: Was part of a much larger movement across the Sahel. Moreover, the evidence for material culture changes between the Pre-Tichitt and Early Tichitt periods appears to suggest that people started to farm millet more intensively around this time. Much of the archeological data associated with the Pre-Tichitt period points to a relatively simple and widespread pastoralist economy incorporating herding of cows, sheep, and goats with hunting of antelope and freshwater fish. Initially, Munson viewed

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