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158-773: Dogu’a Tembien holds numerous prehistoric sites, which have been dated to the Middle Stone Age in Ayninbirkekin , or Pastoral Neolithic in Aregen and Menachek . The lowest places are where the main rivers leave the district. They are often located not far from the highest points, what indicates the magnitude of the relief Since ages, major footpaths and roads in Dogu’a Tembien have been using mountain passes, called ksad , what means “neck” in Tigrinya language . Place names show that

316-418: A mid-ocean ridge , where the volcanic rock is still relatively young, most parts of the seafloor are covered in sediment . This material comes from several different sources and is highly variable in composition. Seafloor sediment can range in thickness from a few millimetres to several tens of kilometres. Near the surface seafloor sediment remains unconsolidated, but at depths of hundreds to thousands of metres

474-406: A pronaos (1960s), the rock church has cruciform columns, flat beams and a flat ceiling, a single arch, and a flat rear wall without apse. Windows give light to the church itself. Emperor Yohannes IV was baptised in this church. The Yohannes rock church at Debre Sema’it ( 13°34.62′N 39°2.24′E  /  13.57700°N 39.03733°E  / 13.57700; 39.03733 ) is located in

632-604: A 70-metres long horizontal gallery, holds underground springs. Numerous other unexplored cave entrances are visible in Antalo Limestone cliffs. Like several other districts in Tigray , Dogu'a Tembien has a number of rock-hewn churches . These have literally been hewn from rock, mainly between the 10th and 14th centuries. The almost inaccessible Dabba Selama monastery ( 13°41.67′N 39°6.03′E  /  13.69450°N 39.10050°E  / 13.69450; 39.10050 )

790-444: A Petri dish. In areas where diatoms are abundant, the underlying sediment is rich in silica diatom tests, and is called diatomaceous earth . Radiolarians are planktonic protozoans (making them part of the zooplankton), that like diatoms, secrete a silica test. The test surrounds the cell and can include an array of small openings through which the radiolarian can extend an amoeba-like "arm" or pseudopod. Radiolarian tests often display

948-421: A change in conditions, such as a change in temperature, pressure, or pH, which reduces the amount of a substance that can remain in a dissolved state. There is not a lot of hydrogenous sediment in the ocean compared to lithogenous or biogenous sediments, but there are some interesting forms. In hydrothermal vents seawater percolates into the seafloor where it becomes superheated by magma before being expelled by

1106-461: A cluster of trees. The church was established in widened caves of the tufa plug. Just outside the district, on the western slopes of the Dogu’a Tembien massif, there are seven other rock churches. Mika’el Samba ( 13°42.56′N 39°6.81′E  /  13.70933°N 39.11350°E  / 13.70933; 39.11350 ) is a rock church hewn in Adigrat Sandstone . It holds grave cells off

1264-519: A crucial element of the symbolic behavioral package in the MSA. Although the advent of anatomical physical modernity cannot confidently be linked with palaeoneurological change, it does seem probable that hominid brains evolved through the same selection processes as other body parts. Genes that promoted a capacity for symbolism may have been selected for, suggesting that the foundations for symbolic culture may well be grounded in biology. However, behavior that

1422-504: A few phonolite plugs in Dogu’a Tembien. The present geomorphology is marked by deep valleys, eroded as a result of the regional uplift. Throughout the Quaternary deposition of alluvium and freshwater tufa occurred in the valley bottoms. In Dogu’a Tembien, there are two main fossil-bearing geological units. The Antalo Limestone ( upper Jurassic ) is the largest. Its marine deposits comprise mainly benthic marine invertebrates . Also,

1580-449: A few millimetres per million years. For that reason, they only form in areas where there are low rates of lithogenous or biogenous sediment accumulation, because any other sediment deposition would quickly cover the nodules and prevent further nodule growth. Therefore, manganese nodules are usually limited to areas in the central ocean, far from significant lithogenous or biogenous inputs, where they can sometimes accumulate in large numbers on

1738-408: A few millimetres to several tens of kilometres. Near the surface, the sea-floor sediments remain unconsolidated, but at depths of hundreds to thousands of metres (depending on the type of sediment and other factors) the sediment becomes lithified . The various sources of seafloor sediment can be summarized as follows:  The distributions of some of these materials around the seas are shown in

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1896-556: A few orange or lemon trees. Grivet monkeys are common and prevent growing of bananas. At several places, people have excavates caves in the sandstone. The larger ones, and most known are the TPLF caves in Addi Geza'iti . Here, in the 1980s, the party established underground rooms and offices cut out in sandstone cliffs, the TPLF carried out its political activities, including a major land reform; it

2054-443: A global scale. So cosmogenous and hydrogenous sediments can mostly be ignored in the discussion of global sediment patterns. Coarse lithogenous/terrigenous sediments are dominant near the continental margins as land runoff , river discharge , and other processes deposit vast amounts of these materials on the continental shelf . Much of this sediment remains on or near the shelf, while turbidity currents can transport material down

2212-458: A greater ability to manufacture symbolic artifacts and social networks. According to the research team in Jebel Irhoud , the discovery means that Homo sapiens —not members of a rival or ancestor species ( Homo heidelbergensis , Homo naledi )—were the ones who left behind Middle Stone Age hand tools that have since been unearthed all over Africa. Numerous sites in southern Africa reflect

2370-473: A higher proportion of O18 isotope. This means the ratio of O16:O18 in shells is low during periods of colder climate. When climate warms, glacial ice melts releasing O16 from the ice and returning it to the oceans, increasing the O16:O18 ratio in the water. When organisms incorporate oxygen into their shells, the shells will contain a higher O16:O18 ratio. Scientists can therefore examine biogenous sediments, calculate

2528-463: A mental template of the process they would follow), possibly using pyrotechnology to facilitate fat extraction from bone, using a probable recipe to produce the compound, and the use of shell containers for mixing and storage for later use. Ochre is reported from some early MSA sites, for example at Kapthurin and Twin Rivers, and is common after c. 100 ka. Barham argues that even if some of this ochre

2686-422: A much faster rate, so they accumulate below their point of origin before the currents can disperse them. Most of the tests do not sink as individual particles; about 99% of them are first consumed by some other organism, and are then aggregated and expelled as large fecal pellets , which sink much more quickly and reach the ocean floor in only 10–15 days. This does not give the particles as much time to disperse, and

2844-517: A natural cave of 20 metres by 20 metres. The roof of the cave is covered with sooth, evidencing the fact that the villagers took cover here, during the Italian bombardments of the Tembien battles in the mid-1930s. The Kidane Mihret rock church at Ab’aro ( 13°44.5′N 39°12.06′E  /  13.7417°N 39.20100°E  / 13.7417; 39.20100 ), is surrounded by tufa plugs, springs and

3002-588: A new level of innovation in their increased efficacy and more complex manufacturing process. The ability to conceptualize beyond the mere reduction of stone cores demonstrates cognitive flexibility, and the use of glue, which was often processed with ochre, to attach flakes to hafts demonstrates an understanding of chemical changes that can be utilized beyond the simple use of color. Adhesives were used to construct hafted tools by 70ka at Sibudu Cave in South Africa. Many of these adhesives were made from local conifers of

3160-504: A number of interlocking CaCO 3 plates (coccoliths) that form a sphere surrounding the cell. When coccolithophores die the individual plates sink out and form an ooze. Over time, the coccolithophore ooze lithifies to becomes chalk. The White Cliffs of Dover in England are composed of coccolithophore-rich ooze that turned into chalk deposits. Foraminiferans (also referred to as forams ) are protozoans whose tests are often chambered, similar to

3318-476: A number of rays protruding from their shells which aid in buoyancy. Oozes that are dominated by diatom or radiolarian tests are called siliceous oozes . Like the siliceous sediments, the calcium carbonate, or calcareous sediments are also produced from the tests of microscopic algae and protozoans; in this case the coccolithophores and foraminiferans. Coccolithophores are single-celled planktonic algae about 100 times smaller than diatoms. Their tests are composed of

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3476-456: A rate of about one centimetre per thousand years, while small clay particles are deposited in the deep ocean at around one millimetre per thousand years. Sediments from the land are deposited on the continental margins by surface runoff , river discharge , and other processes. Turbidity currents can transport this sediment down the continental slope to the deep ocean floor. The deep ocean floor undergoes its own process of spreading out from

3634-450: A remarkable advance. These data have been used to support theories of social and stylistic development throughout the MSA. In southern Africa, we see the technocomplexes of Howiesons Poort and Stillbay , named after the sites at which they were first discovered. Several others have not been dated or have been dated unreliably; these include the Lupemban technocomplex of central Africa,

3792-441: A small church is behind a waterfall 100 meters high. The Dabo Zellelew cave in Aregen at a height of about 2000 metres, has been explored over 14.4 m but its distance is claimed to be way longer ( 13°37′19″N 39°01′59″E  /  13.621862°N 39.033077°E  / 13.621862; 39.033077 ). It contains lithic tools, potsherds, engravings and paintings of Pastoral Neolithic age. The Mihdar Ab’ur cave in

3950-446: A thorough, albeit significantly overlapping, discussion of behavioral modernity. As early Homo sapiens began to diversify the ecological zones that they inhabited during the MSA, the archaeological record associated with these zones begins to show evidence for regional continuities. These continuities are significant for a number of reasons. The expansion of Homo sapiens into various ecological zones demonstrates an ability to adapt to

4108-544: A total population for this woreda of 89,037, of whom 44,408 were men and 44,629 were women. The largest ethnic group reported in Dogu'a Tembien was the Tigrayan (99.87%). Tigrinya was spoken as a first language by 99.89%. Concerning education , 7% of the population were considered literate, which was less than the Zone average of 14%; 8% of children aged 7–12 were in primary school; 0.14% of

4266-458: A total population of 113,595, an increase of 28% over the 1994 census, of whom 56,955 were men and 56,640 women; 7,270 or 6.4% were urban inhabitants. A total of 25,290 households were counted in this woreda, resulting in an average of 4.5 persons per household, and 24,591 housing units. The majority of the inhabitants said they practiced Ethiopian Orthodox Christianity , with 99.89% reporting that as their religion. The 1994 national census reported

4424-575: A variety of environmental contexts including marine environments, savanna grasslands, relatively arid deserts, and forests. This adaptability is reflected in MSA artifacts found in these zones. These artifacts display stylistic variability depending on zone. During the Acheulian, which spanned from 1.5 million years ago to 300 thousand years ago, lithic technology displayed incredible homogeneity throughout all ecological niches. MSA technologies, with their evidence for regional variability and continuity, represent

4582-557: A way that best fits a scenario in which historical contingencies and environmental rather than cognitive changes are seen as main drivers". There have been two migration events out of Africa. The first was the expansion of H. erectus into Eurasia approximately 1.9 to 1.7 million years ago, and the second, by H. sapiens began during the MSA by 80 – 50 ka MSA out of Africa to Asia, Australia and Europe. Perhaps only in small numbers initially, but by 30 ka they had replaced Neanderthals and H. erectus . Each of these migrations represent

4740-657: A wide range of environments, including coastal and inland areas of southern and eastern Africa, and in at least one case MSA foragers were exploiting high-altitude glaciated environments, at Fincha Habera in Ethiopia. This, however, is not the only evidence of innovativeness that can be seen in early Homo sapiens. The development of new, regionally relevant tools, such as those used for the collection of marine resources seen at Abdur, Ethiopia, Pinnacle Point Cave, South Africa, and Blombos Cave , South Africa. The use of fire demonstrates another innovative aspect of human behavior when it

4898-434: Is a bioessential element and is efficiently recycled in the marine environment through the silica cycle . Distance from land masses, water depth and ocean fertility are all factors that affect the opal silica content in seawater and the presence of siliceous oozes. The term calcareous can be applied to a fossil, sediment, or sedimentary rock which is formed from, or contains a high proportion of, calcium carbonate in

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5056-454: Is a common mineral in terrestrial rocks, and it is very hard and resistant to abrasion. Over time, particles made from other materials are worn away, leaving only quartz behind. Beach sand is a very mature sediment; it is composed primarily of quartz, and the particles are rounded and of similar size (well-sorted). Marine sediments can also classified by their source of origin. There are four types:  Lithogenous or terrigenous sediment

5214-403: Is a form of calcium carbonate derived from planktonic organisms that accumulates on the sea floor . This can only occur if the ocean is shallower than the carbonate compensation depth . Below this depth, calcium carbonate begins to dissolve in the ocean, and only non-calcareous sediments are stable, such as siliceous ooze or pelagic red clay . Where and how sediments accumulate will depend on

5372-433: Is a rather primitive rock church, protected from the weather by a pronaos that surrounds the entrance. The church comprises two circular well-carved cells that are used for baptisms. Above the sanctuary there is a series of small blind arcades. Beside the ancient church, a new cave is under excavation. Down from the church there are irrigated tropical gardens. Under cover trees, farmers grow coffee , local hops ( gesho ), and

5530-777: Is a type of biogenic pelagic sediment located on the deep ocean floor . Siliceous oozes are the least common of the deep sea sediments, and make up approximately 15% of the ocean floor. Oozes are defined as sediments which contain at least 30% skeletal remains of pelagic microorganisms. Siliceous oozes are largely composed of the silica based skeletons of microscopic marine organisms such as diatoms and radiolarians . Other components of siliceous oozes near continental margins may include terrestrially derived silica particles and sponge spicules. Siliceous oozes are composed of skeletons made from opal silica Si(O 2 ) , as opposed to calcareous oozes , which are made from skeletons of calcium carbonate organisms (i.e. coccolithophores ). Silica (Si)

5688-409: Is also an ancient rock-hewn church in freshwater tufa , and still in use. The church of Kurkura Mika’el ( 13°40′N 39°9′E  /  13.667°N 39.150°E  / 13.667; 39.150 ), in a very scenic position in a small forest behind limestone pinnacles, is some 30 years old ( File:Antalo Limestone at Kurkura.jpg ). Behind it, the remnant of the earlier church established in

5846-483: Is another way to categorize sediment texture. Sorting refers to how uniform the particles are in terms of size. If all of the particles are of a similar size, such as in beach sand , the sediment is well-sorted. If the particles are of very different sizes, the sediment is poorly sorted, such as in glacial deposits . A third way to describe marine sediment texture is its maturity, or how long its particles have been transported by water. One way which can indicate maturity

6004-413: Is assumed to be the first monastery established in Ethiopia, by Saint Frumentius . The intrepid visitor will climb down, then scramble over narrow ledges along precipices, and finally climb an overhanging cliff. The mesa also comprises a church hewn in Adigrat Sandstone , in shape of a small basilica . The carvers attempted to establish four bays as well as with a recess . The pillars are rounded (which

6162-462: Is common at tropical latitudes, the contrasts between day and night air temperatures are much larger than seasonal contrasts. The rainfall pattern, however, shows a very high seasonality with 70 to 80% of the annual rain falling in July and August. The annual seasons are “hagay” (dry season in winter), “belgi” (spring rains), “kremti” (main summer rains) and “qew'i” (autumn), when the crops are ripening off. In

6320-705: Is difficult to find beyond 40ka, and indirect evidence is essentially intangible, thus technological evidence is the most fruitful of the three. Today there is widespread agreement among archaeologists that the world's first art and symbolic culture dates to the African Middle Stone Age. Some of the most striking artifacts, including engraved pieces of red ochre, were manufactured at Blombos Cave in South Africa 75,000 years ago. Pierced and ochred Nassarius shell beads were also recovered from Blombos, with even earlier examples (Middle Stone Age, Aterian ) from

6478-535: Is during this time that we see evidence of the origins of modern human behavior . According to McBrearty and Brooks, there are four features that are characteristic of modern human behavior: abstract thinking, the ability to plan and strategize, "behavioral, economic and technological innovativeness," and symbolic behavior. Many of these aspects of modern human behavior can be broken down into more specific categories, including art, personal adornment, technological advancement, yet these four overarching categories allow for

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6636-479: Is hewn in Tertiary silicified limestone , high up near the top to of the mountain. As a roof, a thin covering basalt layer was ingeniously used. The columns have a slightly cruciform plan and hold bracket capitals . Itsiwto Maryam rock church ( 13°40′N 39°1′E  /  13.667°N 39.017°E  / 13.667; 39.017 ) is hewn in Adigrat Sandstone . The church has a continuous hipped ceiling to

6794-474: Is how round the particles are. The more mature a sediment the rounder the particles will be, as a result of being abraded over time. A high degree of sorting can also indicate maturity, because over time the smaller particles will be washed away, and a given amount of energy will move particles of a similar size over the same distance. Lastly, the older and more mature a sediment the higher the quartz content, at least in sediments derived from rock particles. Quartz

6952-609: Is in an apse. The sophisticated plan comprises a central axis and two open courtyards that cut deep into the rock. The newly hewn Medhanie Alem rock church in Mt. Werqamba ( 13°42.86′N 39°00.27′E  /  13.71433°N 39.00450°E  / 13.71433; 39.00450 ) is in a central, smaller peak (in Adigrat Sandstone ). Northwest of Abiy Addi , the Geramba rock church ( 13°38.84′N 39°1.55′E  /  13.64733°N 39.02583°E  / 13.64733; 39.02583 )

7110-583: Is no evidence of crossover in this region. ESA Acheulean sites are well documented across West Africa (except from the most tropical regions) but mostly remain undated. A few late Acheulean sites ("MSA" in the sense of late Acheulean, not Levallois) have been dated. Middle Pleistocene (pre 126 kya) sites are known from the northern Sahelian zones, while Late Pleistocene (post 126 kya) sites are known both from northern and southern West Africa. Unlike elsewhere in Africa, MSA sites appear to persist until very late, down to

7268-505: Is no formal discrimination , and all have adopted Tigrinya language and identify as Tigrayans today. However, when it comes to marriage, in-laws may informally verify the ancestry of bride or groom. Dogu’a Tembien comprises 24 tabias or municipalities (status 2019), which have been mapped with their boundaries: Based on the 2007 national census conducted by the Central Statistical Agency of Ethiopia (CSA), this woreda had

7426-414: Is primarily composed of small fragments of preexisting rocks that have made their way into the ocean. These sediments can contain the entire range of particle sizes, from microscopic clays to large boulders, and they are found almost everywhere on the ocean floor. Lithogenous sediments are created on land through the process of weathering, where rocks and minerals are broken down into smaller particles through

7584-465: Is thought to have come from river discharge, particularly from Asia. Most of this sediment, especially the larger particles, will be deposited and remain fairly close to the coastline, however, smaller clay particles may remain suspended in the water column for long periods of time and may be transported great distances from the source. Wind: Windborne (aeolian) transport can take small particles of sand and dust and move them thousands of kilometres from

7742-511: Is uncommon) and expand at either end, supporting arches that appear as triangles. Women are not allowed to do the ascent, nor to visit monastery or church. Independently from the difficult access to the monastery, the surrounding sandstone geomorphology is unique. The Amani’el church in May Baha ( 13°40′N 39°5.4′E  /  13.667°N 39.0900°E  / 13.667; 39.0900 ) has also been carved in Adigrat Sandstone . Behind

7900-418: Is used in order to create stronger tools, such as the heated silcrete at Blombos, Howiesons Poort and Still Bay, and the heat treated bone tools from Still Bay. Hafted tools are further representative of human innovation. The large cutting tools of the Acheulian technocomplex become smaller, as more complex tools are better suited towards the needs of highly diversified environments. Composite tools represent

8058-429: Is very resistant to abrasion, so it is a dominant component of lithogenous sediments, including sand. Biogenous sediments come from the remains of living organisms that settle out as sediment when the organisms die. It is the "hard parts" of the organisms that contribute to the sediments; things like shells, teeth or skeletal elements, as these parts are usually mineralized and are more resistant to decomposition than

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8216-640: The Bambatan in southeast Africa, 70–80ka, and the Aterian technocomplex of northern Africa, 160–90ka. Evidence of abstract thinking can be seen in the archaeological record as early as the Acheulean–Middle Stone Age transition, approximately 300,000–250,000 years ago. This transition involves a shift in stone tool technology from Mode 2, Acheulean tools, to Mode 3 and 4, which include blades and microliths. The manufacture of these tools requires planning and

8374-655: The Howiesons Poort (c. 70–55 ka) is indicative of modern human behavior . A family basis to foraging groups, color symbolism and the reciprocal exchange of artifacts and the formal organization of living space are, he suggests, further evidence for modernity in the MSA. Lyn Wadley et al. have argued that the complexity of the skill needed to process the heat-treated compound glue (gum and red ochre) used to haft spears would seem to argue for continuity between modern human cognition and that of humans 70,000 BP at Sibudu Cave . In 2008, an ochre processing workshop likely for

8532-680: The Kapthurin Formation in Kenya and Kathu Pan in South Africa. Backed pieces from the Twin Rivers and Kalambo Falls sites in Zambia , dated at sometime between 300 and 140,000 years, likewise indicate a suite of new behaviors. A high level of technical competence is also indicated for the c. 280 ka blades recovered from the Kapthurin Formation, Kenya . The stone tool technology in use during

8690-760: The Omo Kibish Formation , the Herto Member of the Bouri Formation , and Mumba Cave contain fossil evidence to support this conclusion as well. There have been a number of theories proposed regarding the development of modern human behavior, but in recent years the mosaic approach has been the most favored perspective in regards to the MSA, especially when taken in consideration with the archaeological evidence. Some scholars including Klein have argued for discontinuity, while others including McBrearty and Brooks have argued that cognitive advances can be detected in

8848-686: The Taforalt Caves . In addition, ostrich egg shell containers engraved with geometric designs dating to 60,000 years ago were found at Diepkloof , South Africa, beads and other personal ornamentation have been found from Morocco which might be as much as 130,000 years old, and the Cave of Hearths in South Africa has yielded a number of beads dating from significantly prior to 50,000 years ago. At Panga ya Saidi in Kenya, marine shell beads appear perhaps as early as 67,000 years ago and certainly by 33,000 years ago, and engraved ochre by 48,500 years ago. Evidence for

9006-843: The Tertiary lacustrine deposits , interbedded in the basalt formations, contain a range of silicified mollusc fossils. In the Antalo Limestone : large Paracenoceratidae cephalopods ( nautilus ); Nerineidae indet.; sea urchins ; Rhynchonellid brachiopod ; crustaceans ; coral colonies ; crinoid stems. In the Tertiary silicified lacustrine deposits : Pila (gastropod) ; Lanistes sp.; Pirenella conica ; and land snails ( Achatinidae indet.). All snail shells, both fossil and recent, are called t’uyo in Tigrinya language , which means ‘ helicoidal ’. The vast areas with outcropping Antalo Limestone hold numerous caves. At Zeyi ( 13°33′N 39°9′E  /  13.550°N 39.150°E  / 13.550; 39.150 ),

9164-768: The baseflow of the river. Also in Ferrey , on the slopes of the Tsaliet gorge, resurgences allow to irrigate gardens with tropical fruits. Middle Stone Age The Middle Stone Age (or MSA ) was a period of African prehistory between the Early Stone Age and the Late Stone Age . It is generally considered to have begun around 280,000 years ago and ended around 50–25,000 years ago. The beginnings of particular MSA stone tools have their origins as far back as 550–500,000 years ago and as such some researchers consider this to be

9322-423: The continental margins where they can be over 10 km thick. This is because the crust near passive continental margins is often very old, allowing for a long period of accumulation, and because there is a large amount of terrigenous sediment input coming from the continents. Near mid-ocean ridge systems where new oceanic crust is being formed, sediments are thinner, as they have had less time to accumulate on

9480-421: The diatoms (algae) and the radiolarians ( protozoans ). Diatoms are particularly important members of the phytoplankton, functioning as small, drifting algal photosynthesizers. A diatom consists of a single algal cell surrounded by an elaborate silica shell that it secretes for itself. Diatoms come in a range of shapes, from elongated, pennate forms, to round, or centric shapes that often have two halves, like

9638-584: The karst aquifer . The large resurgence in Rubaksa ( 13°35′N 39°14′E  /  13.583°N 39.233°E  / 13.583; 39.233 ) irrigates an oasis in a dry limestone gorge. At Inda Mihtsun ( 13°33′N 39°21′E  /  13.550°N 39.350°E  / 13.550; 39.350 ), the May Bilbil resurgence is inside the bed of the Giba River; in the dry season spring water surges through

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9796-418: The seafloor . These particles either have their origins in soil and rocks and have been transported from the land to the sea, mainly by rivers but also by dust carried by wind and by the flow of glaciers into the sea, or they are biogenic deposits from marine organisms or from chemical precipitation in seawater, as well as from underwater volcanoes and meteorite debris. Except within a few kilometres of

9954-435: The start of this article ↑ shows the distribution of the major types of sediment on the ocean floor. Cosmogenous sediments could potentially end up in any part of the ocean, but they accumulate in such small abundances that they are overwhelmed by other sediment types and thus are not dominant in any location. Similarly, hydrogenous sediments can have high concentrations in specific locations, but these regions are very small on

10112-526: The African continent, conventionally divided into five regions: northern Africa, comprising parts of the modern countries of Morocco, Algeria, Tunisia, and Libya; eastern Africa, stretching roughly from the highlands of Ethiopia to the southern part of Kenya; central Africa, stretching from the borders of Tanzania and Kenya to include Angola; southern Africa, which includes the numerous cave sites of South Africa; and western Africa. In northern and western Africa,

10270-465: The Bahamas. Methane hydrates are another type of hydrogenous deposit with a potential industrial application. All terrestrial erosion products include a small proportion of organic matter derived mostly from terrestrial plants. Tiny fragments of this material plus other organic matter from marine plants and animals accumulate in terrigenous sediments, especially within a few hundred kilometres of shore. As

10428-464: The Central African site of Katanda dating to about 90,000 years ago. The arrows and needle, along with hide working tools, from Sibudu Cave are seen as evidence of making weapons with compound heat treated gluing technology. Evidence also exists for the systematic heat treating of silcrete stone to increase its flake-ability for the purpose of toolmaking, beginning approximately 164,000 years ago at

10586-536: The Central Rift Valley of Kenya constituted a major center for behavioural innovation. It is likely that the large terrestrial mammal biomass of these regions supported substantial human populations with subsistence and manufacturing patterns similar to those of ethnographically known foragers. Archaeological evidence from eastern Africa extending from the Rift Valley from Ethiopia to northern Tanzania represents

10744-542: The Holocene boundary (12 kya), pointing to the possibility of late survival of archaic humans , and late hybridization with H. sapiens in West Africa. Furthermore, such results highlight significant spatiotemporal cultural variability and suggest that long inter-group cultural differences played a major role in later stages of human evolution in Africa. Early blades have been documented as far back as 550–500,000 years in

10902-438: The MSA and that the origin of our species is linked with the appearance of Middle Stone Age technology at 250–300 ka. The earliest remains of Homo sapiens date back to approximately 300 thousand years ago in Africa. The continent was mainly populated by groups of hunter-gatherers . In the archaeological record of both eastern Africa and southern Africa, there is immense variability associated with Homo sapiens sites, and it

11060-637: The Mediterranean Sea. Beginning around 6 million years ago, tectonic processes closed off the Mediterranean Sea from the Atlantic, and the warm climate evaporated so much water that the Mediterranean was almost completely dried out, leaving large deposits of salt in its place (an event known as the Messinian Salinity Crisis ). Eventually the Mediterranean re-flooded about 5.3 million years ago, and

11218-645: The Middle Stone Age is presented in Marwick (2003) in which the distance between the source of raw material and location in which a stone artifact was found was compared throughout sites containing early stone artifacts. Five Middle Stone Age sites contained distances between 140–340 km and have been interpreted, when compared with ethnographic data, that these distances were made possible through exchange networks. Barham also views syntactic language as one aspect of behavior that in fact allowed MSA people to settle in

11376-607: The Middle Stone Age shows a mosaic of techniques. Beginning approximately 300 kya, the large cutting tools of the Achuelian are gradually displaced by Levallois prepared core technologies, also widely used by Neanderthals during the European Middle Palaeolithic . As the MSA progresses, highly varied technocomplexes become common throughout Africa and include pointed artifacts, blades, retouched flakes, end and side scrapers, grinding stones, and even bone tools. However,

11534-482: The Middle Stone Age shows a pattern of innovation followed by disappearance. This occurs with technology such as the manufacture of shell beads , arrows and hide working tools including needles, and gluing technology. These pieces of evidence provide a counterpoint to the classic "Out of Africa" scenario in which increasing complexity accumulated during the Middle Stone Age. Instead, it has been argued that such technological innovations "appear, disappear and re-appear in

11692-550: The O16:O18 ratios for samples of known ages, and from those ratios, infer the climate conditions under which those shells were formed. The same types of measurements can also be taken from ice cores; a decrease of 1 ppm O18 between ice samples represents a decrease in temperature of 1.5°C. The primary sources of microscopic biogenous sediments are unicellular algaes and protozoans (single-celled amoeba-like creatures) that secrete tests of either calcium carbonate (CaCO 3 ) or silica (SiO 2 ). Silica tests come from two main groups,

11850-487: The South African site of Pinnacle Point and becoming common there for the creation of microlithic tools at about 72,000 years ago. Characteristically modern human behaviors, such as the making of shell beads, bone tools and arrows, and the use of ochre pigment, are evident at Panga ya Saidi in Kenya by 78,000–67,000 years ago. Evidence of early stone-tipped projectile weapons (a characteristic tool of Homo sapiens ),

12008-522: The Tembien Tigrayans or Tembienot were partly Agew in the past; still nowadays, there are Agew speakers in Abergele , directly southwest of Dogu’a Tembien. The population of Dogu’a Tembien is composed of the original population with a certain admixture of descendants of slaves and serfs who were brought from southwestern Ethiopia, and were in the service of bigger land owners during feudality. There

12166-566: The ability to plan subsistence strategies based on this awareness demonstrates an ability to think beyond the present tense and act upon this knowledge. This planning depth is also seen in the presence of exotic raw materials at a variety of sites throughout the MSA. Procurement of local raw materials would have been a simple task to accomplish, yet MSA sites regularly contain raw materials that were obtained from sources over 100 km away, and sometimes farther than 300 km. Obtaining raw materials from this distance would require an awareness of

12324-405: The action of wind, rain, water flow, temperature- or ice-induced cracking, and other erosive processes. These small eroded particles are then transported to the oceans through a variety of mechanisms:  Streams and rivers: Various forms of runoff deposit large amounts of sediment into the oceans, mostly in the form of finer-grained particles. About 90% of the lithogenous sediment in the oceans

12482-480: The actual end of the Achaeulean around 130 kya is taken as the beginning of the MSA. The MSA so defined is associated with the gradual replacement of archaic humans by anatomically modern humans . In a different convention, MSA refers to sites characterized by the use of Levallois methods for flake production, to the exclusion of Acheulean sites with large cleavers or handaxes. Following McBrearty and Tryon (2006),

12640-448: The amount of material coming from a source, the distance from the source, the amount of time that sediment has had to accumulate, how well the sediments are preserved, and the amounts of other types of sediments that are also being added to the system. Rates of sediment accumulation are relatively slow throughout most of the ocean, in many cases taking thousands of years for any significant deposits to form. Lithogenous sediment accumulates

12798-403: The atmosphere that eventually settle back down to Earth and contribute to the sediments. Like spherules, meteor debris is mostly silica or iron and nickel. One form of debris from these collisions are tektites , which are small droplets of glass. They are likely composed of terrestrial silica that was ejected and melted during a meteorite impact, which then solidified as it cooled upon returning to

12956-631: The beginnings of the MSA. The MSA is often mistakenly understood to be synonymous with the Middle Paleolithic of Europe, especially due to their roughly contemporaneous time span; however, the Middle Paleolithic of Europe represents an entirely different hominin population, Homo neanderthalensis , than the MSA of Africa, which did not have Neanderthal populations. Additionally, current archaeological research in Africa has yielded much evidence to suggest that modern human behavior and cognition

13114-400: The bottom! Given that slow descent, a current of only 1 cm/sec could carry the test as much as 15,000 km away from its point of origin before it reaches the bottom. Despite this, the sediments in a particular location are well-matched to the types of organisms and degree of productivity that occurs in the water overhead. This means the sediment particles must be sinking to the bottom at

13272-420: The bottom. While calcite is insoluble in surface water, its solubility increases with depth (and pressure) and at around 4,000 m, the carbonate fragments dissolve. This depth, which varies with latitude and water temperature, is known as the carbonate compensation depth . As a result, carbonate oozes are absent from the deepest parts of the ocean (deeper than 4,000 m), but they are common in shallower areas such as

13430-484: The centre aisle. There are carved diagonal crosses as well as a cross carved above the arch into the sanctuary. The ceiling holds longitudinal beams that form a continuous lintel, which is similar to traditional Tigrayan workmanship. The church is at risk of collapse and hence access is not permitted. The Kidane Mihret rock church of Addi Nefas ( 13°33.3′N 39°1.44′E  /  13.5550°N 39.02400°E  / 13.5550; 39.02400 ) in Adigrat Sandstone

13588-452: The children aged 13–14 were in junior secondary school, and 0.21% of the inhabitants aged 15–18 were in senior secondary school. Concerning sanitary conditions , about 29% of the urban houses and 15% of all houses had access to safe drinking water at the time of the census; 6% of the urban and 2.4% of the total had toilet facilities. As of 2020, Dogu'a Tembien's territory belongs to the following new woredas: The East African Orogeny led to

13746-492: The climate-change implications of its extraction and use can see that this would be folly. Cosmogenous sediment is derived from extraterrestrial sources, and comes in two primary forms; microscopic spherules and larger meteor debris. Spherules are composed mostly of silica or iron and nickel, and are thought to be ejected as meteors burn up after entering the atmosphere. Meteor debris comes from collisions of meteorites with Earth. These high impact collisions eject particles into

13904-409: The coccolithophores that also produced calcium carbonate tests. Discoaster tests were star-shaped, and reached sizes of 5-40 μm across. Discoasters went extinct approximately 2 million years ago, but their tests remain in deep, tropical sediments that predate their extinction. Because of their small size, these tests sink very slowly; a single microscopic test may take about 10–50 years to sink to

14062-453: The continental shelf and reach the deep ocean floor. Lithogenous sediments usually reflect the composition of whatever materials they were derived from, so they are dominated by the major minerals that make up most terrestrial rock. This includes quartz, feldspar, clay minerals, iron oxides, and terrestrial organic matter. Quartz (silicon dioxide, the main component of glass) is one of the most common minerals found in nearly all rocks, and it

14220-584: The deepest parts of the ocean, and most of this clay is terrestrial in origin. Siliceous oozes (derived from radiolaria and diatoms) are common in the south polar region, along the equator in the Pacific, south of the Aleutian Islands, and within large parts of the Indian Ocean. Carbonate oozes are widely distributed in all of the oceans within equatorial and mid-latitude regions. In fact, clay settles everywhere in

14378-440: The diagram at the start of this article ↑ . Terrigenous sediments predominate near the continents and within inland seas and large lakes. These sediments tend to be relatively coarse, typically containing sand and silt, but in some cases even pebbles and cobbles. Clay settles slowly in nearshore environments, but much of the clay is dispersed far from its source areas by ocean currents. Clay minerals are predominant over wide areas in

14536-473: The earliest MSA sites. Faunal preservation, however, is not spectacular, and standardization in site excavation and lithic classification was, until recently, lacking. Unlike northern Africa, shifts between lithic technologies were not nearly as pronounced, likely due to more favorable climatic conditions that would have allowed for more continuous occupation of sites. Central Africa reflects similar patterning to eastern Africa, yet more archaeological research of

14694-425: The extraction of these non-renewable resources. Evaporites are hydrogenous sediments that form when seawater evaporates, leaving the dissolved materials to precipitate into solids, particularly halite (salt, NaCl). In fact, the evaporation of seawater is the oldest form of salt production for human use, and is still carried out today. Large deposits of halite evaporites exist in a number of places, including under

14852-557: The fastest, on the order of one metre or more per thousand years for coarser particles. However, sedimentation rates near the mouths of large rivers with high discharge can be orders of magnitude higher. Biogenous oozes accumulate at a rate of about 1 cm per thousand years, while small clay particles are deposited in the deep ocean at around one millimetre per thousand years. As described above, manganese nodules have an incredibly slow rate of accumulation, gaining 0.001 millimetres per thousand years. Marine sediments are thickest near

15010-464: The fleshy "soft parts" that rapidly deteriorate after death. Macroscopic sediments contain large remains, such as skeletons, teeth, or shells of larger organisms. This type of sediment is fairly rare over most of the ocean, as large organisms do not die in enough of a concentrated abundance to allow these remains to accumulate. One exception is around coral reefs ; here there is a great abundance of organisms that leave behind their remains, in particular

15168-513: The foot of the massif) to younger, near the summits. From Palaeozoic to Triassic , Dogu’a Tembien was located near the South Pole. The (reactivate) Precambrian extensional faults guided the deposition of glacial sediments ( Edaga Arbi Glacials and Enticho Sandstone ). Later alluvial plain sediments were deposited ( Adigrat Sandstone ). The break-up of Gondwana ( Late Palaeozoic to Early Triassic ) led to an extensional tectonic phase , what caused

15326-415: The form of calcite or aragonite . Calcareous sediments ( limestone ) are usually deposited in shallow water near land, since the carbonate is precipitated by marine organisms that need land-derived nutrients. Generally speaking, the farther from land sediments fall, the less calcareous they are. Some areas can have interbedded calcareous sediments due to storms, or changes in ocean currents. Calcareous ooze

15484-420: The form of shellfish exploitation for food. Based on his analysis of the MSA bovid assemblage at Klasies , Milo reports MSA people were formidable hunters and that their social behavior patterns approached those of modern humans. Deacon maintains that the management of plant food resources through deliberate burning of the veld to encourage the growth of plants with corms or tubers in the southern Cape during

15642-676: The four characteristics of behavioral modernity. Blombos Cave , South Africa contains personal ornaments and what are presumed to be the tools used for the production of artistic imagery, as well as bone tools. Still Bay and Howieson's Poort contain variable tool technologies. These different types of assemblages allow researchers to extrapolate behaviors that would likely be associated with such technologies, such as shifts in foraging behaviors, which are further supported by faunal data at these sites. Marine sediments Marine sediment , or ocean sediment , or seafloor sediment , are deposits of insoluble particles that have accumulated on

15800-562: The fragments of the stony skeletons of corals that make up a large percentage of tropical sand. Microscopic sediment consists of the hard parts of microscopic organisms, particularly their shells, or tests . Although very small, these organisms are highly abundant and as they die by the billions every day their tests sink to the bottom to create biogenous sediments. Sediments composed of microscopic tests are far more abundant than sediments from macroscopic particles, and because of their small size they create fine-grained, mushy sediment layers. If

15958-555: The future, but decreased spring rains. About three quarters of Dogu’a Tembien (800 km) drains to Giba River , and the remaining quarter (240 km) to the Weri’i River . The general drainage is westward, to the Tekezze River. Main tributaries in Dogu’a Tembien, from upstream to downstream, are At the lower part of the Antalo Limestone , where it lies on the Adigrat Sandstone , there are high discharge resurgences that drain

16116-473: The genus Podocarpus , using a process based on distillation. Other technological innovations of the period include specialized projectile weapons found at various sites in Middle Stone Age Africa such as: bone and stone arrowheads at South African sites such as Sibudu Cave (along with an early bone needle also found at Sibudu) dating approximately 60,000–70,000 years ago, and bone harpoons at

16274-613: The gradual displacement of Acheulian by MSA technologies is further supported by this layering and contemporaneous placement, as well as by the earliest appearance of MSA technologies at Gademotta and the latest Acheulian technologies at the Bouri Formation of Ethiopia, dated to 154 to 160 kya. This suggests a possible overlap of 100–150 thousand years. Late Acheulean artefacts associated with Homo sapiens have been found in South African cave sites. The Cave of Hearths and Montague Cave in South Africa contain evidence of Acheulian technologies, as well as later MSA technologies, however there

16432-516: The growth of a mountain chain in the Precambrian (up to 800 million years ago or Ma), that was largely eroded afterwards. Around 600 Ma, the Gondwana break-up led to the presence of tectonic structures and a Palaeozoic planation surface , that extents to the north and west of the Dogu'a Tembien massif. Subsequently, there was the deposition of sedimentary and volcanic formations, from older (at

16590-419: The halite deposits were covered by other sediments, but they still remain beneath the seafloor. Oolites are small, rounded grains formed from concentric layers of precipitation of material around a suspended particle. They are usually composed of calcium carbonate, but they may also from phosphates and other materials. Accumulation of oolites results in oolitic sand, which is found in its greatest abundance in

16748-461: The increased flexibility of the genus Homo to survive in widely varied climates. Based on the measurement of a large number of human skulls a recent study supports a central/southern African origin for Homo sapiens as this region shows the highest intra-population diversity in phenotypic measurements. Genetic data supports this conclusion. However, there is genetic evidence to suggest that dispersal out of Africa began in eastern Africa. Sites such as

16906-513: The isotopes). O16 is the most common form, followed by O18 (O17 is rare). O16 is lighter than O18, so it evaporates more easily, leading to water vapor that has a higher proportion of O16. During periods of cooler climate, water vapor condenses into rain and snow, which forms glacial ice that has a high proportion of O16. The remaining seawater therefore has a relatively higher proportion of O18. Marine organisms which incorporate dissolved oxygen into their shells as calcium carbonate will have shells with

17064-509: The largest archaeological evidence of the shift from the Late Acheulian to the Middle Stone Age tool technologies. This transition is characterized by stratigraphic layering of Acheulian stone tools, a bifacial handaxe technology, underneath and even contemporaneous with MSA technologies, such as Levallois tools, flakes, flaked tools, pointed flakes, smaller bifaces that are projectile in form, and, on rare occasions, hafted tools. Evidence of

17222-426: The largest with grain diameters of 256 mm or larger. Among other things, grain size represents the conditions under which the sediment was deposited. High energy conditions, such as strong currents or waves, usually results in the deposition of only the larger particles as the finer ones will be carried away. Lower energy conditions will allow the smaller particles to settle out and form finer sediments. Sorting

17380-622: The low temperatures typical of the seafloor (close to 4 °C), water and methane combine to create a substance known as methane hydrate. Within a few metres to hundreds of metres of the seafloor, the temperature is low enough for methane hydrate to be stable and hydrates accumulate within the sediment. Methane hydrate is flammable because when it is heated, the methane is released as a gas. The methane within seafloor sediments represents an enormous reservoir of fossil fuel energy. Although energy corporations and governments are anxious to develop ways to produce and sell this methane, anyone that understands

17538-505: The lowering of large parts of the Horn of Africa . As a consequence a marine transgression occurred, leading to the deposition of marine sediments ( Antalo Limestone and Agula Shale). At the end of the Mesozoic tectonic phase, a new ( Cretaceous ) planation took place. After that, the deposition of continental sediments ( Amba Aradam Formation ) indicates the presence of less shallow seas, what

17696-400: The main church, there are elongated chambers, maybe been the beginnings of an ambulatory . To enter the church, one has to go down a few. Remarkably, at the entrance, a pool of water is fed by a spring. The Welegesa church ( 13°43′N 39°4′E  /  13.717°N 39.067°E  / 13.717; 39.067 ) is hewn in Adigrat Sandstone . The entrance to the church is part of

17854-483: The main space. As Mika'el Samba is not a village church, priests are only present on the monthly Mika’els day, the twelfth day in the Ethiopian calendar . The Maryam Hibeto rock church ( 13°42.67′N 39°6.44′E  /  13.71117°N 39.10733°E  / 13.71117; 39.10733 ) is located at the edge of a church forest. It is hewn in Adigrat Sandstone , with a pronaos in front of it. On both sides of

18012-427: The making of paints by a complex process also exists dating to 100,000 years ago in South Africa, and for the use of pigments in Kenya dating to about 320,000 years ago. A series of innovations have been documented by 170–160,000 years ago at the site of Pinnacle Point 13B on the southern Cape coast of South Africa . This includes the oldest confirmed evidence for the utilization of ochre and marine resources in

18170-636: The mid-Atlantic ridge, the East Pacific Rise (west of South America), along the trend of the Hawaiian/Emperor Seamounts (in the northern Pacific), and on the tops of many isolated seamounts. Sediment texture can be examined in several ways. The first way is grain size . Sediments can be classified by particle size according to the Wentworth scale . Clay sediments are the finest with a grain diameter of less than .004 mm and boulders are

18328-555: The mid-ocean ridge, and then slowly subducts accumulated sediment on the deep floor into the molten interior of the earth. In turn, molten material from the interior returns to the surface of the earth in the form of lava flows and emissions from deep sea hydrothermal vents , ensuring the process continues indefinitely. The sediments provide habitat for a multitude of marine life , particularly of marine microorganisms . Their fossilized remains contain information about past climates , plate tectonics , ocean circulation patterns, and

18486-472: The monumental Zeyi Abune Aregawi church holds the entrance to Northern Ethiopia's largest cave. The 364-metres long oval gallery displays stalactites , stalagmites , decametre-high columns, bell-holes following joints, and speleothems on walls and floor. The 145-metres long Zeleqwa horizontal gallery is located in a cliff nearby the river of the same name ( 13°38′N 39°7′E  /  13.633°N 39.117°E  / 13.633; 39.117 ). At

18644-450: The more diversified toolkit of the Middle Stone Age, as well as in the subsistence patterns of the period. As MSA hominins began to migrate into a range of different ecological zones, it became necessary to base hunting strategies around seasonally available resources. Awareness of seasonality is evident in the faunal remains found at temporary sites. In less forgiving ecological zones, this awareness would have been essential for survival and

18802-470: The most difficult aspects of modern human behavior to distinguish archaeologically. When searching for evidence of symbolic behavior in the MSA, there are three lines of evidence that can be considered: direct evidence reflecting concrete examples of symbols; indirect evidence reflecting behaviors that would have been used to convey symbolic thought; and technological evidence reflecting the tools and skills that would have been used to produce art. Direct evidence

18960-411: The nodule to grow over time. The composition of the nodules can vary somewhat depending on their location and the conditions of their formation, but they are usually dominated by manganese- and iron oxides. They may also contain smaller amounts of other metals such as copper, nickel and cobalt. The precipitation of manganese nodules is one of the slowest geological processes known; they grow on the order of

19118-443: The ocean and begins to break apart or melt, these particles get deposited. Most of the deposition will happen close to where the glacier meets the water, but a small amount of material is also transported longer distances by rafting, where larger pieces of ice drift far from the glacier before releasing their sediment. Gravity: Landslides, mudslides, avalanches, and other gravity-driven events can deposit large amounts of material into

19276-489: The ocean are gastroliths. Gastrolith means "stomach stone". Many animals, including seabirds, pinnipeds, and some crocodiles deliberately swallow stones and regurgitate them latter. Stones swallowed on land can be regurgitated at sea. The stones can help grind food in the stomach or act as ballast regulating buoyancy. Mostly these processes deposit lithogenous sediment close to shore. Sediment particles can then be transported farther by waves and currents, and may eventually escape

19434-444: The ocean when they happen close to shore. Waves: Wave action along a coastline will erode rocks and will pull loose particles from beaches and shorelines into the water. Volcanoes: Volcanic eruptions emit vast amounts of ash and other debris into the atmosphere, where it can then be transported by wind to eventually get deposited in the oceans. Gastroliths : Another, relatively minor, means of transporting lithogenous sediment to

19592-452: The oceans, but in areas where silica- and carbonate-producing organisms are prolific, they produce enough silica or carbonate sediment to dominate over clay. Carbonate sediments are derived from a wide range of near-surface pelagic organisms that make their shells out of carbonate. These tiny shells, and the even tinier fragments that form when they break into pieces, settle slowly through the water column, but they don't necessarily make it to

19750-456: The possible making of projectile points. It is observed by the authors of three 2018 studies on the site, that the evidence of these behaviors is approximately contemporary to the earliest known Homo sapiens fossil remains from Africa (such as at Jebel Irhoud and Florisbad ), and they suggest that complex and modern behaviors had already begun in Africa around the time of the emergence of Homo sapiens . Symbolic behavior is, perhaps, one of

19908-571: The pre- trap rock topography was more elevated in Dogu'a Tembien as compared to more southerly areas. Three major formations may be distinguished: lower basalts , interbedded lacustrine deposits and upper basalts . Almost at the same time, the Mekelle Dolerite intruded the Mesozoic sediments following joints and faults . A new magma intrusion occurred in the Early Miocene , what gave rise to

20066-440: The production of paints was uncovered dating to ca. 100,000 years ago at Blombos Cave, South Africa. Analysis shows that a liquefied pigment-rich mixture was produced and stored in the two abalone shells, and that ochre, bone, charcoal, grindstones and hammer-stones also formed a composite part of the toolkits. Evidence for the complexity of the task includes procuring and combining raw materials from various sources (implying they had

20224-528: The region is certainly required. Southern Africa consists of many cave sites, most of which show very punctuated starts and stops in stone tool technology. Research in southern Africa has been continuous and quite standardized, allowing for reliable comparisons between sites in the region. Much of the archaeological evidence for the origins of modern human behavior is traced back to sites in this region, including Blombos Cave , Howiesons Poort , Still Bay , and Pinnacle Point . The term "Middle Stone Age" (MSA)

20382-441: The resources, a perceived value in the resources, whether it be functional or symbolic, and, possibly, the ability to organize an exchange network in order to obtain the materials. The ability to expand into new environments throughout Africa and, ultimately, the world, displays a level of adaptability and, consequently, innovativeness that is often seen as characteristic of behavioral modernity. Middle Stone Age sites are found in

20540-422: The rock, forming two courtyards , both hewn but not open at the upper side. The first courtyard holds graves; between the two, there is a block of stone with a cross in the window opening in its centre. The three-aisled church has a depth of four bays. There are entrances on both sides through hewn corridors. The church ceiling has a consistent height, holding cupolas, arches and capitals in each bay. The hewn tabot

20698-476: The seafloor (Figure 12.4.2 right). Because the nodules contain a number of commercially valuable metals, there has been significant interest in mining the nodules over the last several decades, although most of the efforts have thus far remained at the exploratory stage. A number of factors have prevented large-scale extraction of nodules, including the high costs of deep sea mining operations, political issues over mining rights, and environmental concerns surrounding

20856-435: The seafloor and the other half suspected from water column indicators and/or seafloor deposits. Manganese nodules are rounded lumps of manganese and other metals that form on the seafloor, generally ranging between 3–10 cm in diameter, although they may sometimes reach up to 30 cm. The nodules form in a manner similar to pearls; there is a central object around which concentric layers are slowly deposited, causing

21014-497: The sediment becomes lithified (turned to rock). Rates of sediment accumulation are relatively slow throughout most of the ocean, in many cases taking thousands of years for any significant deposits to form. Sediment transported from the land accumulates the fastest, on the order of one metre or more per thousand years for coarser particles. However, sedimentation rates near the mouths of large rivers with high discharge can be orders of magnitude higher. Biogenous oozes accumulate at

21172-415: The sediment below will reflect the production occurring near the surface. The increased rate of sinking through this mechanism has been called the "fecal express". Seawater contains many different dissolved substances. Occasionally chemical reactions occur that cause these substances to precipitate out as solid particles, which then accumulate as hydrogenous sediment. These reactions are usually triggered by

21330-403: The sediment layer consists of at least 30% microscopic biogenous material, it is classified as a biogenous ooze. The remainder of the sediment is often made up of clay. Biogenous sediments can allow the reconstruction of past climate history from oxygen isotope ratios. Oxygen atoms exist in three forms, or isotopes, in ocean water: O16 , O17 and O18 (the number refers to the atomic masses of

21488-436: The sediments pile up, the deeper parts start to warm up (from geothermal heat), and bacteria get to work breaking down the contained organic matter. Because this is happening in the absence of oxygen (a.k.a. anaerobic conditions), the by-product of this metabolism is the gas methane (CH 4 ). Methane released by the bacteria slowly bubbles upward through the sediment toward the seafloor. At water depths of 500 m to 1,000 m, and at

21646-444: The shells of snails. As the organism grows, is secretes new, larger chambers in which to reside. Most foraminiferans are benthic, living on or in the sediment, but there are some planktonic species living higher in the water column. When coccolithophores and foraminiferans die, they form calcareous oozes . Older calcareous sediment layers contain the remains of another type of organism, the discoasters ; single-celled algae related to

21804-416: The source. These small particles can fall into the ocean when the wind dies down, or can serve as the nuclei around which raindrops or snowflakes form. Aeolian transport is particularly important near desert areas. Glaciers and ice rafting : As glaciers grind their way over land, they pick up lots of soil and rock particles, including very large boulders, that get carried by the ice. When the glacier meets

21962-504: The stone tips of javelins or throwing spears, were discovered in 2013 at the Ethiopian site of Gademotta , and date to around 279,000 years ago. Evidence was found in 2018, dating to about 320,000 years ago, at the Kenyan site of Olorgesailie , of the early emergence of innovations and behaviors including: long-distance trade networks (involving goods such as obsidian), the use of pigments, and

22120-478: The summer rainy season the dominant wind direction is from the southwest, whereas in the rest of the year winds blow from the east. The farmers have adapted their cropping systems to this spatio-temporal variability in rainfall. Given the good chilling conditions , it is possible to grow apple at elevations above 2400 metres, such as in Dingilet or Mashih . Climate models predict intensified summer rainfall in

22278-458: The surface. Cosmogenous sediment is fairly rare in the ocean and it does not usually accumulate in large deposits. However, it is constantly being added to through space dust that continuously rains down on Earth. About 90% of incoming cosmogenous debris is vaporized as it enters the atmosphere, but it is estimated that 5 to 300 tons of space dust land on the Earth's surface each day. Siliceous ooze

22436-539: The term "early MSA" (EMSA) refers to sites predating the 126 kya interglacial, and "later MSA" (LMSA) refers to site younger than 126 kya. In this convention, Fauresmith sites of 500 to 300 kya are within the ESA, and the MSA begins after about 280 kya and is largely associated with H. sapiens , the earliest reliably dated MSA site in East Africa being Gademotta in Ethiopia, at 276 kya. The Middle Awash valley of Ethiopia and

22594-463: The timing of major extinctions . Except within a few kilometres of a mid-ocean ridge , where the volcanic rock is still relatively young, most parts of the seafloor are covered in sediments. This material comes from several different sources and is highly variable in composition, depending on proximity to a continent, water depth, ocean currents, biological activity, and climate. Seafloor sediments (and sedimentary rocks ) can range in thickness from

22752-541: The top of a rock pinnacle that overlooks Addi Nefas village. This church has also been hewn in Adigrat Sandstone . The Lafa Gebri’al rock church ( 13°35.87′N 39°17.25′E  /  13.59783°N 39.28750°E  / 13.59783; 39.28750 ) is now disused. It was hewn in a tufa plug. The church boosts a semi-circular wooden arch of approx. 1.5 metre across (in one piece). Ruba Bich’i 's village church ( 13°36′N 39°18′E  /  13.600°N 39.300°E  / 13.600; 39.300 )

22910-544: The tropical forest environments of what is now the Democratic Republic of the Congo . Many authors have speculated that at the core of this symbolic explosion, and in tandem, was the development of syntactic language that evolved through a highly specialized social learning system providing the means for semantically unbounded discourse. Syntax would have played a key role in this process and its full adoption could have been

23068-494: The understanding of how striking a stone will produce different flaking patterns. This requires abstract thought, one of the hallmarks of modern human behavior. The shift from large cutting tools in the Acheulian to smaller and more diversified toolkits in the MSA represents a better cognitive and conceptual understanding of flintknapping, as well as the potential functional effects of distinct tool types. The ability to plan and strategize, much like abstract thinking, can be seen in

23226-547: The upper side of the cliff, there is an alignment of cavities: the “windows” of a gallery parallel to cliff and river. The cave floor holds with clay pots that would have served as food containers for villagers who went there hiding during an early 20th C. conflict. The Tinsehe caves, a cave system opening into the Upper Tsaliet River gorge near Addi Idaga ( 13°42′N 39°12′E  /  13.700°N 39.200°E  / 13.700; 39.200 ). The entrance near

23384-633: The use of blades (associated mainly with the Upper Palaeolithic in Europe) is seen at many sites as well. In Africa, blades may have been used during the transition from the Early Stone Age to the Middle Stone Age onwards. Finally, during the later part of the Middle Stone Age, microlithic technologies aimed at producing replaceable components of composite hafted tools are seen from at least 70 ka at sites such as Pinnacle Point and Diepkloof Rock Shelter in South Africa. Artifact technology during

23542-585: The vent. This superheated water contains many dissolved substances, and when it encounters the cold seawater after leaving the vent, these particles precipitate out, mostly as metal sulfides. These particles make up the "smoke" that flows from a vent, and may eventually settle on the bottom as hydrogenous sediment. Hydrothermal vents are distributed along the Earth's plate boundaries, although they may also be found at intra-plate locations such as hotspot volcanoes. Currently there are about 500 known active submarine hydrothermal vent fields, about half visually observed at

23700-782: The village of Mahba in Aregen at a height of about 2500 metres, is some 64 m long ( 13°37′14″N 39°03′05″E  /  13.620592°N 39.051313°E  / 13.620592; 39.051313 ). It contains engravings and paintings of Pastoral Neolithic age. The Danei Kawlos cave in the Tsech'i gorge at the west of Menachek at a height of about 2020 metres, is some 13.5 metres long ( 13°37′19″N 39°01′59″E  /  13.621862°N 39.033077°E  / 13.621862; 39.033077 ). It contains lithic tools, potsherds, and faunal remains of Pastoral Neolithic age. The May Hib’o cave ( 13°31′N 39°14′E  /  13.517°N 39.233°E  / 13.517; 39.233 ),

23858-450: The wet-dry cycles of the modern Sahara desert has led to fruitful archaeological sites followed by completely barren soil and vice versa. Preservation in these two regions can vary, yet the sites that have been uncovered document the adaptive nature of early humans to climatically unstable environments. Eastern Africa represents some of the most reliable dates, due to the use of radiocarbon dating on volcanic ash deposits, as well as some of

24016-403: The younger crust. As distance increases from a ridge spreading center the sediments get progressively thicker, increasing by approximately 100–200 m of sediment for every 1000 km distance from the ridge axis. With a seafloor spreading rate of about 20–40 km/million years, this represents a sediment accumulation rate of approximately 100–200 m every 25–50 million years. The diagram at

24174-571: Was beginning to develop much earlier in Africa during the MSA than it was in Europe during the Middle Paleolithic. The MSA is associated with both anatomically modern humans ( Homo sapiens ) as well as archaic Homo sapiens , sometimes referred to as Homo helmei . Early physical evidence comes from the Gademotta Formation in Ethiopia, the Kapthurin Formation in Kenya and Kathu Pan in South Africa. There are MSA archaeological sites from across

24332-571: Was from here that the offensives were organised till the conquest of Addis Ababa in 1991. In nearby Melfa , the Amhara EPDM party had its own headquarters in a cave. As Dogu'a Tembien holds a wide variety of rock types , there is expectedly a varied use of rock. Average annual precipitation (in Hagere Selam ) is 778 mm. Mean temperature is 13.3 °C, oscillating between average daily minimum of 10.9 °C and maximum of 22 °C. As it

24490-491: Was mediated by symbolism may have only come later, even though this physical capacity was already in place much earlier. Skoyles and Sagan, for example, argue that human brain expansion by increasing the prefrontal cortex would have created a brain capable of symbolizing its previously non-symbolic cognition, and that this process, slow to begin with, increasingly accelerated during the last 100,000 years. Symbolically mediated behavior may then feed back upon this process by creating

24648-690: Was probably caused by a regional uplift. In the beginning of the Caenozoic , there was a relative tectonic quiescence, during which the Amba Aradam Sandstones were partially eroded what led to the formation of a new planation surface. In the Eocene , the Afar plume a broad regional uplift deformed the lithosphere , leading to the eruption of flood basalts . The magma followed pre-existing tectonic lineaments. A mere thickness of 400 metres of basalt indicates that

24806-566: Was proposed to the African Archaeological Congress by Goodwin and Van Riet Lowe in 1929. The use of these terms was officially abandoned in 1965, although the term remains in use in the context of sub-Saharan Africa , beginning with a transitional late Acheulean period known as the Fauresmith industry . The Fauresmith industry is poorly dated, according to Herries (2011) beginning around 511–435 kya. This time, rather than

24964-625: Was used in a symbolic, color-related role then this abstraction could not have worked without language. Ochre, he suggests, could be one proxy for trying to find the emergence of language. Formal bone tools are frequently associated with modern behaviour by archaeologists. Sophisticated bone harpoons manufactured at Katanda, West Africa at c. 90 ka and bone tools from Blombos Cave dated at c. 77 ka may then also serve as examples of material culture associated with modern language. Language has been suggested to be necessary to maintain exchange networks. Evidence of some form of exchange networks during

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