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the Dawn of Civilization => Africa, the Cradle of Life => Topic started by: Bianca on August 10, 2008, 08:02:26 am

Post by: Bianca on August 10, 2008, 08:02:26 am

                                                                   The Sahara


The Sahara is the world's second largest desert (second to Antarctica), over 9,000,000 km² (3,500,000 mi²), located in northern Africa and is 2.5 million years old. The entire land area of the United States of America would fit inside it. Its name, Sahara, is an English pronuciation of the word for desert in Arabic.

The boundaries of the Sahara are the Atlantic Ocean on the west, the Atlas Mountains and the Mediterranean Sea on the north, the Red Sea and Egypt on the east, and the Sudan and the valley of the River Niger on the south. The Sahara is divided into western Sahara, the central Ahaggar Mountains, the Tibesti massif, the Aïr Mountains (a region of desert mountains and high plateaus), Tenere desert and the Libyan desert (the most arid region). The highest peak in the Sahara is Emi Koussi (3415 m) in the Tibesti Mountains in northern Chad.

The Sahara divides the continent into North and Sub-Saharan Africa. The southern border of the Sahara is marked by a band of semiarid savanna called the Sahel; south of the Sahel lies the lusher Sudan.

Humans have lived on the edge of the desert for almost 500,000 years. During the last ice age, the Sahara was a much wetter place, much like East Africa, than it is today. Over 30,000 petroglyphs of river animals such as crocodiles survive in total with half found in the Tassili n'Ajjer in southeast Algeria. Fossils of dinosaurs have also been found here. The modern Sahara, though, is generally devoid of vegetation, except in the Nile Valley and at a few oases and in some scattered mountains and has been this way since about 3000 BC.

2.5 million people live in the Sahara, most of these in Mauritania, Morocco and Algeria. Dominant groups of people are the Tuareg-Berber, the Sahrawis, Moors, and different black African ethnicities including the Tubu, the Nubians, the Zaghawas and the Kanuri. The largest city is Nouakchott, Mauritania's capital. Other important cities are Tamanrasset, Algeria; Timbuktu, Mali; Agadez, Niger; Ghat, Libya; and Faya, Chad.

By 2500 BC the Sahara was as dry as it is today and it became a largely impenetrable barrier to humans, with only scattered settlements around the oases, but little trade or commerce through the desert. The one major exception was the Nile Valley. This well watered section of the desert became one of the most densely populated regions on the planet and the home to one of humanity's earliest civilizations. The Nile, however, was impassable at several cataracts making trade and contact difficult. Over time Egypt spread south and technologies such as iron working, and perhaps ideas such as that of monarchy spread into Nubia and further south.

Sometime between 633 and 530 BC Hanno the Navigator either established or reinforced Phoenician colonies in the Western Sahara, but all ancient remains have vanished with virtually no trace

By 500 BC a new influence arrived in the form of the Greeks and Phoenicians. Greek traders spread along the eastern coast of the desert, establishing trading colonies along the Red Sea coast. The Carthaginians explored the Atlantic coast of the desert. The turbulence of the waters and the lack of markets never led to an extensive presence further south than modern Morocco. Centralized states thus surrounded the desert on the north and east; it remained outside of the control of these states. Raids from the nomadic Berber people of the desert were a constant concern of those living on the edge of the desert.

The greatest change in the history of the Sahara arrived with the Arab invasion that brought camels to the region. For the first time an efficient trade across the Sahara desert could be conducted. The kingdoms of the Sahel grew rich and powerful exporting gold to North Africa. The emirates along the Mediterranean sent south manufactured goods and horses. From the Sahara itself salt was exported. This process turned the scattered oasis communities into trading centres, and brought them under the control of the empires on the edge of the desert.

This trade persisted for several centuries until the development in Europe of the caravel allowed ships, first from Portugal but soon from all Western Europe, to sail around the desert and gather the resources from the source in Guinea. The Sahara was rapidly remarginalized.

The colonial powers also largely ignored the region, but the modern era has seen a number of mines and communities develop to exploit the desert's natural resources. These include large deposits of oil and gas in Algeria and Libya and large deposits of phosphates in Morocco and Western Sahara.


This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Sahara".

Title: Re: The Sahara
Post by: Bianca on August 10, 2008, 08:15:40 am

                              The prehistory of Western Sahara in a regional context

Nick Brooks1, Savino Di Lernia2 and Nick Drake3
1Tyndall Centre for Climate Change Research and School of Environmental Sciences, University of East
Anglia, Norwich NR4 7TJ, UK. Email;
2Department of Scienze Storiche, Archeologiche, e Antropologiche dell’Antichità, Faculty of Human
Sciences, University of Rome “La Sapienza”, Via Palestro 63, 00185 – Rome, Italy. E-mail:
3Department of Geography, King’s College, Strand, London WC2R 2LS. Email:
Extended Abstract

The disputed territory of Western Sahara has long been inaccessible to research as a result of the militaryand political conflict between Morocco, which occupies some eighty per cent of the territory, and the Frente Polisario, the Algeria-based Western Saharan independence movement.

This paper presents the findings of a two-week reconnaissance survey of the archaeology and environment of the Northern Sector of the Polisario-controlled zone of Western Sahara (Figure 1),
which took place in September and October 2002, and comprised researchers from the UK and Italy.

The results of the survey are described within thecontext of their relevance to the archaeology and environmental history of the wider Saharan region, after a consideration of the general environmental history of he Sahara as a whole.

The cultural history of the Sahara is intimately related to the existence of a succession of humid and
arid episodes, which in turn are associated with periods of global warming and cooling respectively.

Evidence from throughout the Sahara indicates that the region experienced a cool, dry and windy
climate during the last glacial period, followed by a wetter climate with the onset of the current interglacial, with humid conditions being fully established by around 10,000 BP, when we see the first evidence of a reoccupation of parts of the central Sahara by hunter gathers, most likely originating from sub-Saharan Africa
(Cremaschi and Di Lernia, 1998; Goudie, 1992; Phillipson, 1993; Ritchie, 1994; Roberts, 1998).

The cycle of glacial desiccation followed by interglacial greening is believed to be driven predominantly by variations in northern hemisphere insolation resulting from changes in the tilt of the Earth’s axis associated with the precessional cycle (Roberts, 1998).

Stronger insolation leads to increased heating of the NorthAfrican subcontinent, intensifying the African Monsoon which penetrates deep into the Sahara.

Superimposed on the interglacial humid episodes are brief periods of aridity lasting from decades to
centuries, broadly coincident with cold events in the Atlantic that appear to be manifestations of internal
climate variability that
(Alley et al. 1997; Bond et al., 1997; Cremaschi et al., 2001, 2002; Di Lernia and Palombini, 2002).

In the early Holocene, when northern hemisphere summer insolation was strong, these arid episodes were followed by recovery; however, the onset of aridity around 5000 BP was followed by a
long-term desiccation throughout the Sahara
(Cremaschi, 1998; Jolly et al. 1998; Lioubimsteva 1995).

Title: Re: The Sahara
Post by: Bianca on August 10, 2008, 08:19:44 am

While there is a high degree of homogeneity in the Saharan palaeoclimatic record on multi-millennial
timescales (Jolly et al., 1998; Lezine, 1989; Petit-Maire et al., 1997), the timings of arid episodes and the onset of environmental desiccation are not identical at all locations (Alley et al., 1997; Gasse and vanCampo, 1994; Goodfriend, 1991; Smith, 1998).

This may be explained by a combination of geographical differences in the nature of the principal rain-bearing systems (particularly at the extremities of the Sahara), and the mediation of climate change impacts by local surface environments. The impacts of the final climatic desiccation of the Sahara on human populations would have been strongly mediated by the rapidity and nature of the corresponding environmental desiccation. Where surface water disappeared rapidly,human populations would have been forced to migrate to wetter areas; however, in certain areas populations undertook local adaptation to gradual desiccation by exploiting refugia in which water remained as a consequence of the near-surface geology or occasional rainfall resulting from local topography
(Di Lernia et al., 2002; Mattingly et al., 2003).

The area investigated during the 2002 field survey in Western Sahara is situated between the present
day zones of westerly Atlantic rain-bearing systems to the north-west and monsoonal rainfall to the south, and is characterised by numerous ephemeral river channels. While further research is necessary to develop a detailed environmental chronology for the study area, two radiocarbon dates indicate wetter conditions in the region in the seventh millennium BP, with water present in one of the now-dry lakes in the fifth millennium BP
(Brooks et al., 2003).

These preliminary results are broadly consistent with data from the central Sahara indicating an early-middle Holocene humid episode followed by middle-late Holocene desiccation
(Petit-Maire et al., 1997).

Title: Re: The Sahara
Post by: Bianca on August 10, 2008, 08:26:37 am

Archaeological materials also indicate significant commonality with other Saharan regions. Acheulian
and Aterian materials, and a single trihedral point, indicate that the study area was occupied in the
Pleistocene, although the density of materials suggests that occupation may have been in the form of small, transient groups.

The density of burial sites indicates a much larger population in the Holocene, and Holocene microlithic material were also recorded.

In particular, funerary monuments representing a wide range of typologies reflect the material culture of
the central Sahara. Conical tumuli, platform burials and a V-type monument represent structures similar to those found in other Saharan regions and associated with human burials, appearing in sixth millennium BP onwards in northeast Niger and southwest Libya (Sivilli, 2002).

In the latter area a shift in emphasis from faunal to human burials, complete by the early fifth millennium BP, has been interpreted by Di Lernia and Manzi (2002) as being associated with a change in social organisation that occurred at a time of increasing aridity.

While further research is required in order to place the funerary monuments of Western Sahara in
their chronological context, we can postulate a similar process as a hypothesis to be tested, based on thehigh density of burial sites recorded in the 2002 survey.

A monument consisting of sixty five stelae was also of great interest; precise alignments north and east,
a division of the area covered into separate units, and a deliberate scattering of quartzite inside the
structure, are suggestive of an astronomical function associated with funerary rituals. Stelae are also
associated with a number of burial sites, again suggesting dual funerary and astronomical functions (Figure 2).

Further similarities with other Saharan regions are evident in the rock art recorded in the study area,
although local stylistic developments are also apparent. Carvings of wild fauna at the site of Sluguilla
resemble the Tazina style found in Algeria, Libya and Morocco (Pichler and Rodrigue, 2003), although
examples of elephant and rhinoceros in a naturalistic style reminiscent of engravings from the central
Sahara believed to date from the early Holocene are also present.

The situation at Sluguilla is unusual in that carvings are located on isolated, largely horizontal limestone slabs exposed to the elements (Figure 3).

Title: Re: The Sahara
Post by: Bianca on August 10, 2008, 08:32:20 am

The combination of familiar Saharan subjects and local stylistic innovation is also apparent at the
previously recorded sites of Erqeiz and Irghayra (Soler et al, 1999) and the newly identified site of Bou
Dheir (Brooks et al, 2003).

These sites are all located along elevated areas overlooking wide plains, in contrast to Sluguilla, and are associated with paintings rather than carvings. Erqeiz and Bou Dheir arenotable for their representations of large wild fauna, familiar from the central Sahara in the form of engravings
(Dupuy, 1999, Jelínek, 2000; Phillipson, 1993).

At Rekeiz an elephant and rhinoceros are depicted on the same vertical rock face in a location some distance from the main concentrations of paintings, while an elephant and a buffalo are recorded at Bou Dheir in close proximity to representations of human figures, hand prints, cattle, gazelle and a large painting that may be a wild or domesticated ovicaprid.

Giraffe are represented in paintings at Bou Dheir and Rekeiz, and in engravings at Sluguilla,indicating that they occupied an important role in the lives of the prehistoric peoples of the region, as they
did throughout the Sahara
(Dupuy, 1999; van Hoek, 2003).

Cattle feature prominently in the rock art of the Northern Sector, particularly at Erqueiz. They are also
represented at Bou Dheir, in a particularly distinctive painted style. A remarkable isolated engraving of a
cow with a smaller animal depicted inside the stomach, presumably an infant or unborn calf, was recordedon a rock at the edge of a plateau on which were located a number of funerary monuments, includingplatform and corbeille structures (Figure 4).

These images illustrate that cattle were crucial to the lives of the prehistoric peoples of Western Sahara, as they were throughout the Sahara
(e.g. Di Lernia and Palombini, 2002; Holl and Dueppen, 1999).

Ovicaprids are also a common theme in the rock paintings of the study area, although it is difficult to determine whether these images represent domestic or wild animals.

At Rekeiz and Irghrayra sheep or goats are depicted in long lines consisting of many animals. The
dominant painted panel at Bou Dheir is centred on a large image of an animal of uncertain type, possibly anovicaprid or a wild herbivore, but clearly of great significance to the artist or artists (Figure 5).

Title: Re: The Sahara
Post by: Bianca on August 10, 2008, 08:35:59 am

Human figures are represented only in the painted imagery recorded to date; they are absent from the
recorded engravings of Sluguilla, although their presence at unrecorded sites cannot be discounted.

Some of the figures at Bou Dheir are represented with distinctive crests or head-dresses reminiscent
of painted figures of Mediterranean or Near Eastern appearance in the central Sahara, while representations at Erqueiz are very different in appearance, suggesting at least two different population groups.

Despite the large distances involved, it appears that the far west of the Sahara around the latitude of 25°
N was far from isolated from the remainder of the greater Saharan region.

The prehistoric inhabitants of Western Sahara hunted and recorded the same animals as their counterparts
in central and eastern regions, and shared the same technologies. As throughout the Sahara, they responded to the same pressures of climatic and environmental desiccation; the location of hearths within wide river channels suggests a congregation around diminishing water resources, while the depiction of a wide variety of more humid climate fauna indicate Holocene desiccation following a humid phase.

However, many questions remain regarding the chronology of human occupation and the processes of adaptation and cultural evolution.

For example, was the region reoccupied at the same time as the recolonisation of the central Sahara, or did
transient occupation continue through the arid period that preceded the Holocene?

Did changes in funerary practices evolve in situ as societies became more stratified during the final period of desiccation, or were new practices introduced fully formed by migrants from other regions where desiccation was more advanced?

How and when were cattle introduced to the region?

In what directions did migration occur throughout the Holocene?

These questions can only be answered by further extensive research in the region, which is contingent on a continued ceasefire between the parties to the conflict, and ultimately on its peaceful and just resolution.

Title: Re: The Sahara
Post by: Bianca on August 10, 2008, 08:43:43 am


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Brooks, N., di Lernia, S., Drake, N., Raffin, M. and Savage, T. 2003. Geoarchaeology of the Western
Sahara: Preliminary results of the first Anglo-Italian expedition in the liberated zone. Sahara 14: 63-
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Cremaschi, M. and di Lernia, S. 1998. The geoarchaeological survey in central Tadrart Acacus and
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Cremaschi, M., Pelfini, M., Arzuffi, L., Di Mauro, V., Santilli, M. and Zerboni, A. 2001. A palaeoclimatic
record for the late Holocene in the central Sahara: tree rings of Cypressus dupretiana from the Wadi
Tanezzuft area (SW Fezzan, Libya). In Abstracts of the International Conference “Tree Rings and
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Di Lernia, S. and Palombini, A. 2002. Desertification, sustainability, and archaeology: indications from the
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prehistory of the Wadi Tenezzuft, in Sand, Stones and Bones: The Archaeology of Death in the Wadi
Tannezzuft Valley (5000-2000 BP) (Eds. S. Di Lernia and G. Manzi), pp 281-302, Centro
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Dupuy, C. 1999. L’art rupestre à gravures naturalistes de l’Adrar des Iforas (Mali), Sahara 11, 69-86.

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Jelínek, J. 2000. Rock art at I-n-Leludj (Fezzan, Libya), Sahara 12, 159-163.

Title: Re: The Sahara
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van Hoek, M. 2003. The Saharan “giraffe à lien” in rock art. Domesticated giraffe or rian animal?
Comparing enigmatic giraffe petroglyphs from the Sahara and Namibia, Sahara 14, 49-62.

Mattingly, D., Reynolds, T. and Dore, J. 2003. Synthesis of human activities in Fazzan. In The Archaeology of Fazzan: Volume 1, Synthesis (Ed. D. J. Mattingly), pp 327-373. Department of Antiquities, Tripoli and Society for Libyan Studies.

Petit-Maire, N., Beufort, L. and Page, N. 1997. Holocene climate change and man in the present day Sahara desert. In Third Millennium BC Climate Change and Old World Collapse (Eds. H. Nüzhet Dalfes, G.
Kukla and H. Weiss), pp 297-308. Springer-Verlag Berlin Heidelberg.

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Pichler, W. and Rodrigue, A. 2003. The “Tazina style, Sahara 14, 89-106.

Ritchie, J.C. 1994. Holocene pollen spectra from Oyo, northwestern Sudan: problems of interpretation in a hyperarid environment. Holocene 4: 9-15.

Roberts, N. 1998. The Holocene: An Environmental History. Second Edition, Blackwell Publishers Ltd.,

Sivilli, S., 2002, A historical background: mortuary archaeology in the Sahara between colonialism and
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(5000-2000 BP) (Eds. S. Di Lernia and G. Manzi), pp 17-24, Centro Interuniversitario di Ricerca per le
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Smith, A. B. 1998. Intensification and transformation processes towards food production in Africa. In
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ABACO and Centro Interuniversitardo di Ricerca sulle Civiltà e l’Ambiente del Sahara Antico, Rome.


Title: Re: The Sahara
Post by: Bianca on May 16, 2009, 10:31:15 pm

                            Archaeologists Explore Prehistoric Heritage Of The Sahara

May 19th, 2008 -
ICT by admin - 
Madrid, May 19 (ANI):

A team of archaeologists is making the first catalogue of the prehistoric heritage of the Western Sahara.

The team, which comprises of Basque and Sahrawi archaeologists is exploring the region of Tiris, a
vast desert area south of Western Sahara, to find more about the past of this inhospitable region.

Led by Andoni Saenz de Buruaga, a professor at the Basque public university UPV, the team is visiting the Western Sahara for a fifth time.

We presented our research project to the Sahrawi Government in 2004. It was very well received and we have been given every chance. The results are very good, we have really made progress and that encourages us to travel for the fifth time to the region of Tiris, said Saenz de Buruaga.

The research of the Basque archaeologists covers an area of 30,000 km2, three times the surface of Navarre, a region in northern Spain.

In five years work, the Basque archeologists have catalogued more than 300 archaeological sites, including former human settlements, carvings and cave paintings. Most of them are between 3,000
and 10,000 years old.

The research work helps to make the prehistoric heritage of the southern region of the Western
Sahara better known.

We will keep on trying to research the past of the Sahrawis. It is vet important for them to know their cultural heritage, which is very rich opposite to what it was generally thought, said Saenz de Buruaga. It is a way to show and claim that their ancestors lived here, he added.

One of the most remarkable conclusions is the verification that todays arid desert was a subtropical savanna with plenty of flora and fauna six thousand years ago.

Rains decreased as a consequence of a process of climate change and animals moved to other places to face the lack of water.


Post by: Bianca on May 16, 2009, 10:37:51 pm

                                                      Rivers In The Sand -

                    The Ancient Sahara May Have Harbored Waterways And Prehistoric Humans

Science News, 
August 26, 1989 
by Bruce Bower

The Eastern Sahara is one of the hottest places on Earth, its parched sands moistened by a rain shower every few decades. It may come as a surprise, then, that stretches of this African desert have inspired a scientific debate over water.

More specifically, the argument concerns ancient water. From around 2 million to 4,000 years ago, one group of investigators contends, a braided network of channels set into large valleys in the Eastern Sahara filled with flowing water during extended spells of humidity and substantial rainfall. The valleys attracted early humans at least 200,000 years ago, they say.

Another team maintains no such river system ever existed. In their view, fierce desert winds hollowed out depressions in the earth that became temporary ponds or lakes after rains. Human activity at these oases was minimal at best, they conclude.

One thing is sure: The debate owes its existence to the U.S. space program.

The first inkling that the Eastern Sahara once possessed some type of water drainage system came in 1982, when scientists at the U.S. Geological Survey (USGS) in Flagstaff, Ariz., examined radar images of Earth taken during a flight of the space shuttle Columbia. The radar penetrated large areas of the Sahara where the sand sheet is no more than several feet thick, revealing a web of valleys and smaller channels winding beneath the desert sands (SN: 4/21/84, p.224).

In 1984, guided by specially processed maps from Landsat, radar and other sources, USGS researchers located some of the radar-exposed channels with the aid of a satellite navigation device modified for land use. Excavations on the "shores" of two sand-covered valleys, directed by archaeologist William P. McHugh (who died in May), uncovered hand axes and other stone artifacts dating to approximately 200,000 years ago.

The archaeological evidence fits with geological data, described by USGS scientist John F. McCauley and his colleagues in the July 1986 IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, indicating the "radar rivers" are missing links of a previously unrecognized trans-African river system. At least 30 million years ago, the researchers maintain, volcanic eruptions and shifts in the Earth's crust carved out the system's major streams, which flowed southwest from headwaters in Egypt and the Sudan, across northern Africa and into the Atlantic Ocean at the Gulf of Guinea.

The Amazonian proportions of the river system gradually receded. Geological disturbances cut off stream flow at several points in the valleys around 15 million years ago, McCauley's group says. A northward-flowing river arose about 6 million years ago and amputated still-operational sections of the river complex from its headwaters. The onset of extreme heat and virtually no rain around 2 million years ago dealt the final blow.

Nevertheless, the USGS researchers hold, ensuing rainy periods temporarily reactivated some of the rivers and streams in the Eastern Sahara. Archaeological remains indicate the streams drew groups of early humans until about 4,000 years ago, when climate changes made the area unlivable.

Archaeologist Fred Wendorf of Southern Methodist University in Dallas and his co-workers proposed a different interpretation of the radar-exposed channels in the spring 1987 JOURNAL OF FIELD ARCHAEOLOGY. They surveyed several hundred archaeological sites in and around the Eastern Sahara radar channels and concluded that no evidence supports the scenario of an ancient river system once coursing through the area. Over the last 2 million years, according to these investigators, desert winds probably dug out bedrock basins during "hyperarid" periods. The basins collected sediment and water during rainy stretches, creating transient ponds or lakes.

Archaeological sites in the survey represent short-term stops by very small groups of people, Wendorf argues. In his opinion, this confirms that prehistoric water sources in the Eastern Sahara could not support sustained human use.

The USGS scientists charge, however, that Wendorf's survey was conducted in an area where the sand is too thick for radar penetration and thus it sheds no light on the relation of prehistoric sites to the radar-exposed channels.

In a flurry of recent publications, including the winter 1988 JOURNAL OF FIELD ARCHAEOLOGY, the Feb. 24 SCIENCE and the June ANTIQUITY, McHugh and USGS scientists present further evidence for an early occupation of the African desert's ancient valleys. Uranium-series dating of carbonate found along the edges of the valleys indicates the rock was deposited in three episodes -- about 45,000 years ago, 141,000 years ago and 212,000 years ago. These deposits apparently were generated by groundwater present during phases of wet weather, the researchers contend.

McHugh's 1984 excavations, they add, uncovered stone hand axes from the 212,000-year-old carbonate deposits, providing a minimum age estimate for human occupation of the valleys. In McHugh's view, these early inhabitant's were hunters and gatherers, drawn to the game and vegetation near the riverbanks. A long succession of people followed, culminating with groups that raised cattle in the ancient valleys between 7155 and 2900 B.C.

Post by: Bianca on May 16, 2009, 10:40:13 pm

Around that time, according to the USGS group, the drying up to the Sahara reduced water-carrying channels to a few separate water holes, much as the billabongs of the Australian desert now lie along the courses of defunct ancient rivers.

More support for some form of prehistoric water connection in the Sahara, although not necessarily a vast river network, comes from a report soon to appear in QUATERNARY RESEARCH. Excavations conducted in 1987 at a wind-formed basin near the radar-exposed channels yielded several thousand remains of fish, amphibians, reptiles, birds and small mammals, say zoologist Kazimierz Kowalski of the Polish Academy of Sciences in Krakow and his co-workers -- including Wendorf. The fossils came from sediment dated at about 135,000 years old.

Animals uncovered at the site, including crocodiles and water turtles, indicate a large lake was once present, the researchers contend. Annual rainfall at the time was at least 20 inches, they add.

The 1987 excavations also uncovered remains of deep-water fish, now under study by paleontologist Wim Van Neer of the Royal Museum of Central Africa in Tervuren, Belgium. Only through direct water connections can these creatures colonize new areas, Van Neer says. McCauley and his USGS colleagues suggest that around 100,000 years ago, streams represented by the radar-exposed channels hooked up with water sources in the Nile Valley nearly 200 miles to the east.

Wendorf, however, still doubts humans inhabited the area for extended periods. He says the archaeological sites unearthed earthed by McHugh probably represent remains of tool workshops used intermittently over tens of thousands of years.

Althouth McHugh and his co-workers noted in the January 1988 GEOARCHAEOLOGY that their research "has literally only scratched the surface," exporation under the Saharan sands will resume in 1991, when three new space shuttle radar flights are planned. Remarks USGS geologist Carol S. Breed, "We want to map the distribution of ancient river channels across all of northern Africa."

Bibliography for

"Rivers in the sand; the ancient Sahara may have harbored waterways and prehistoric humans"

View more issues:

August 12, 1989,

August 19, 1989,

Sept 2, 1989

Bruce Bower

"Rivers in the sand; the ancient Sahara may have harbored waterways and prehistoric humans".

Science News.
August 26, 1989.
17 Jun. 2008.

Post by: Bianca on May 16, 2009, 10:46:32 pm

                            Archaeologists Explore Prehistoric Heritage Of The Sahara

May 19th, 2008 -
ICT by admin - 
Madrid, May 19 (ANI):

A team of archaeologists is making the first catalogue of the prehistoric heritage of the Western Sahara.

The team, which comprises of Basque and Sahrawi archaeologists is exploring the region of Tiris, a
vast desert area south of Western Sahara, to find more about the past of this inhospitable region.

Led by Andoni Saenz de Buruaga, a professor at the Basque public university UPV, the team is visiting the Western Sahara for a fifth time.

We presented our research project to the Sahrawi Government in 2004. It was very well received and we have been given every chance. The results are very good, we have really made progress and that encourages us to travel for the fifth time to the region of Tiris, said Saenz de Buruaga.

The research of the Basque archaeologists covers an area of 30,000 km2, three times the surface of Navarre, a region in northern Spain.

In five years work, the Basque archeologists have catalogued more than 300 archaeological sites, including former human settlements, carvings and cave paintings. Most of them are between 3,000
and 10,000 years old.

The research work helps to make the prehistoric heritage of the southern region of the Western
Sahara better known.

We will keep on trying to research the past of the Sahrawis. It is vet important for them to know their cultural heritage, which is very rich opposite to what it was generally thought, said Saenz de Buruaga. It is a way to show and claim that their ancestors lived here, he added.

One of the most remarkable conclusions is the verification that todays arid desert was a subtropical savanna with plenty of flora and fauna six thousand years ago.

Rains decreased as a consequence of a process of climate change and animals moved to other places to face the lack of water.


Post by: Bianca on May 16, 2009, 10:51:56 pm

By Louis Werner
By Kevin Bubriski


There are only 233 of them on Earth growing in their native soil. Some are as young as 30 years old;
others may date back two millennia. They can be 22 meters (70') tall and up to 12 meters (38') around.
In the local language, Tamashek, they are named individually, by some attribute:

“The Carpet One” or

“The One by the Flat Stones.”

Many of them drink from seasonal pools. Others must wait for the rare cloudburst to send rainwater rushing past. All somehow have learned to survive in highland “islands” within the world’s largest desert. And only a few people, including Wawa Muhammad Hamid and Muhammad Beddiaf, have seen nearly every one of them.

Hamid is a warden in southeastern Algeria’s Tassili n’Ajjer National Park, and Beddiaf is an archeologist who has walked almost every one of the park’s 100,000 hectares (386 sq mi). What is dear to both their hearts, and what they have sworn to protect, is Cupressus dupreziana—in English, the Saharan cypress, or tarout in Tamashek—listed by the International Union for the Conservation of Nature as one of Earth’s rarest tree species.

In botanical terminology, “young specimens grown in protected conditions are first bushy, later developing
a straight central axis. Bark is reddish-brown, with deep longitudinal fissures.... Branches diverge from the trunk at large angles, curving upwards.... Leaves are cupressoid scales....”

All this makes for a dignified tree, a kind of weather- and drought-beaten version of the Mediterranean cypress (Cupressus sempervirens) immortalized in the paintings of Vincent van Gogh—and all the more impressive for its harsh setting. But this comparison means little to Hamid.

“I played in these trees as a boy,” he says, remembering his childhood as a goatherd. “We took their shade, and used them as meeting points and landmarks. A traveling man might leave his belongings hanging in a bag from their limbs for years at a time, and know that everything would be waiting for him safely whenever he returned.”

Post by: Bianca on May 16, 2009, 10:53:12 pm

Post by: Bianca on May 16, 2009, 10:54:27 pm

To Europeans, conifer trees in the midst of the Sahara had been a rumor since 1860, when the
English explorer H. B. Tristram wrote in his book The Great Sahara: Wanderings South of the Atlas Mountains, “to judge from the woodwork of the [Tuareg] saddles, there is also a species of hard resinous wood probably allied to junipers.” He was close: The Juniperus genus is adjacent to the Cupressus genus within the cypress family, Cupressaceae.

Still, this cypress species was not described scientifically until 1924, after it was seen by the man
for whom it is named, Captain Duprez, commander of French forces at Fort Charlet in the Djanet oasis, at the foot of the nearly 2000-meter-high (6500') Tassili plateau. He wrote to a biologist, “I discovered one day in a small wadi called Tamrit a tree with foliage and habit too unusual for the area not to attract my attention.” At the time, only a handful of these cypresses were said to be in existence, their seeds were thought to be sterile, and their extinction was anticipated in a matter of years.

Today, the Saharan cypress has better chances of survival. In part, this is thanks to investigations
by Algerian paleoecologist Fatiha Abdoun, the one person who has seen every Saharan cypress still alive in its native habitat. Two young trees in Wadi Tamrit, where many are clustered, were thought to have slim odds of survival when French botanists measured them in the 1950’s but, five decades later, Abdoun has found them healthy. Their slow, two-millimeter-per-year radial growth rates compare well with those of their close cousin the Atlas cypress (Cupressus atlantica), whose habitat in Morocco’s High Atlas mountains has an annual rainfall 15 times greater than that of the Tassili. And no less fittingly, that first tree found by Captain Duprez is thought to be still alive and healthy at the head of the wadi.

But if the tree has proved to be successful in germinating, taking root and adapting to increasingly arid conditions, Abdoun says it may not be able to outwit its latest challenge: growing numbers of mostly European tourists, led by the commercial outfitters who have flourished since the end of the Algerian civil war in the late 1990’s. They flock to the Tassili plateau not so much for the trees, but to view a remarkable gallery of late Paleolithic and Neolithic rock art.

Post by: Bianca on May 16, 2009, 11:02:18 pm

There are also more local problems. According to Abdoun’s complete tree census, conducted between 1997 and 2001, the cutting of branches and roots for firewood, and the damage to trees from grazing goats are thought to be responsible for the death of eight percent of the trees first counted in 1972. What she hopes is that the tourism industry “will involve itself more in the protection of the trees and of the area in general,” she says, “for its prosperity comes from the appreciation and conservation of the region as a whole.”

She notes that Henri Lhote, who popularized the region’s prehistoric art in his 1959 book The Search for the Tassili Frescoes, wrote of having to burn newly cut cypress wood in order to cook his expedition’s dinners. “One might almost deduce from this,” she says ironically, “that it was really the tree that discovered the frescoes, and not a man.”

Surprisingly, there is also a threat to the trees from flooding. Wadis, dry most of the year, can run fast and high one minute and go back to dry the next. The cypress’s roots meander wide and shallow—the better to grab diffuse, infrequent surface moisture—but lack a firm-footed taproot. As a result, like other cypress species, the tarout often twists above and among stony streambeds, and is vulnerable to upsets in floods. Such flash floods are as common here as they are in the American Southwest: In June 2005, the popular Tuareg singer Osman Balli was killed when his Land Rover overturned in high water at a wadi crossing in the middle of Djanet, and in January 2006 the northern Tassili town of Illizi was severely damaged in a flood.

A further threat to the tarout comes from African emigrants on their way toward Europe, whose crossings on foot often take them from Djanet to the Libyan border town of Ghat. They must often burn wood to stay alive on winter nights when temperatures can drop below freezing. So many have passed this way that the direct line between the two towns is now denuded. Carpentry is a historical use of tarout wood, but is now less of a threat: An Italian–Libyan archeological expedition examined some cypress-plank doors in Ghat and determined through carbon-14 analysis that the wood was cut at least 500 years ago. Local carpenters now work with other, introduced species, such as eucalyptus.

Post by: Bianca on May 16, 2009, 11:04:02 pm

Muhammad Beddiaf was Abdoun’s co-author on a 2002 scientific paper on the tree census, which reported that, since the early 1970’s, 10 newly germinated trees, in addition to 13 previously uncounted ones, have slightly more than made up for the 20 that had died from cutting and burning.

Beddiaf, a specialist in the area’s rock art, imagines how the trees might be somehow connected to the rock artists. “These cypresses were present at the time of the artists—perhaps not these very same trees, but ones from which these have grown. The artists were surrounded by their greenery. They no doubt relaxed under their branches. So I find it odd that the trees should not be represented in their art.” Except for a few diagrammatic renderings of gardens, dating from the most recent artistic era known as “the camel and horse period,” only hunting and war scenes are represented, in which human and animal figures seem to hang in midair.

Tuareg oral literature too seems bereft of mention of the tarout. At the campfire, Beddiaf has an extensive command of his people’s poetry and song, but when pressed for an ode to the tarout, he can muster only a tribute to other trees—as firewood!

From the fire of the acacia,

Every day it throws off sparks.

From the fire of the iseem plant,

Every day you grill two mouflon.

From the fire of the ajar tree,

Every day you shoot the arrow straight.

From the fire of the tamarisk,

Every day you eat gazelle tripe.

Tarout in Tamashek is originally a butcher’s term for the windpipe and attached lungs of a grazing animal. It is said that the tarout tree, when its slightly asymmetrical crown is in robust foliage, takes on the shape of these organs held windpipe-down, and that the term was applied to the tree because of this resemblance. But trees are often given individual names as well, referring for instance to a person who uses the tree’s limbs to hang his goods on (Tin-Ambarak or Tin-Gaded), or to a local landmark, such as a nearby mountain (Tin-Tamanzazt) or a pool of water at the tree’s roots (Tin-Balalan).

Today, the Saharan cypress is closely studied by botanists, not only because of its rarity, but also because it is the only species in the plant kingdom known to reproduce by cloning its male genetic material through a process known as male apomixis. Female apomixis—the division of female cells inside a flower’s ovary as a means of seed formation—is common in several species, including dandelions and blackberries, but male cloning requires an additional step unique to the Saharan cypress: Pollen, carrying the male cells, enters the tree’s ovule, but instead of combining with the female cells, it divides internally to become a viable seed genetically identical to itself.

Post by: Bianca on May 16, 2009, 11:05:20 pm

“In human terms, this is the equivalent of a mother giving birth to a baby that is genetically unrelated to her, but genetically identical to the father,” explains Richard Primack, professor of biology at Boston University.

An experiment in which pollen from the Cupressus dupreziana was dusted onto the female cones of the Mediterranean cypress, whose resulting seeds were germinated and grown for 15 years, culminated in trees physically similar and identical in their DNA to the “father” tree, but unlike the “mother.” There is no obvious evolutionary advantage to this. If other conifer species were to grow nearby—and they do not—then perhaps the pollen of the Saharan cypress could be said to profit by “borrowing” these other cones, using their ovules merely as incubators. Even so, as in all cloning, this would lead to an evolutionary dead end: genetic invariability and a species not capable of adapting to changing conditions.

Rob Nicholson, head of the Smith College Botanic Garden in Northampton, Massachusetts, collected seeds in 1985 from cypresses in the Tassili to study artificial propagation methods. One tree he germinated in the greenhouse shot up so fast it had to be cut down in order to save the roof. He has sent hundreds of cuttings from seedlings to botanic gardens in Atlanta, Pasadena, Houston and elsewhere. “To see healthy trees growing in the ground that you have started years earlier from small cuttings is almost like seeing your own child graduate from college. You feel they’ve made it!” he says.

But these New World transplants are only the latest that, since the mid-20th century, have been grown outside their home habitat. France’s oldest botanical garden, the Jardin des Plantes in Montpellier, has eight healthy specimens of Saharan cypress, while the Villa Thuret in Antibes, France, which is part of the Institut National de Recherche Agronomique, has grown trees studied closely by Christian Pichot and Muhammad el Maataoui, who first discovered its unique genetic behavior.

It was long known that only about 10 percent of seeds from both wild and cultivated Saharan cypress trees have a viable embryo, so the tree’s low fertility rate was thought to be intrinsic to the species. Pichot and el Maataoui recently determined exactly why: The tree’s meiosis—its cell division prior to reproduction—is wildly erratic. Instead of the pollen dividing neatly in half to create a pair of diploid cells, which contain two sets of chromosomes, it often creates cells containing one or four sets of chromosomes —or none. Only diploid cells can successfully germinate.

Post by: Bianca on May 16, 2009, 11:06:24 pm

A route that takes in about half the Tassili’s 233 known trees covers territory between Wadis Tamrit, Riey, Tichouinet, InGharouhane, Amazar and Tefatast—a good walk of six days covering 160 kilometers (100 mi). Retired Algerian government forester Said Grim covered much the same ground in 1972 when he conducted the first full Saharan cypress census. Supported by a 15-donkey pack string, he traveled for three months, relying on word-of-mouth reports from Tuareg herders he met along the way to direct him to the next tree. Now living in retirement in Montreal, Grim remembers that trip as his career’s greatest challenge. “We tried to find every last tree,” he says, “and I think we were successful.”

Before that, in 1965, the trees in several wadis were photographed by a French botanical team, and many of these same trees can still be seen today—with thicker crowns, due no doubt to the relatively good rains of recent years. The physical descriptions from back then are bleaker than today’s: They speak of uncovered roots, recumbent trunks and mutilated branches. The words peu fructifié (“not thriving”) stand out. Although Beddiaf has not seen some of them since before the rains returned, he is guardedly optimistic.

“I don’t think we have a problem with drought for the moment,” he says as he surveys a large guelta, or pool of standing water. It is big enough to have been given its own name, InWatika, in memory of a man called Watika, who was buried nearby. A flock of pin-tailed sandgrouse, known here as ganga chata, rests beside the pool. Jerboa and fox tracks crisscross the bank. A curious mula-mula, or white-capped black wheatear, hops from branch to branch in an acacia. Clearly there is still life, and the potential for even more life, in this high desert.

A recent study by Abdoun has shown that young cypress trees can take quick advantage of even extremely brief wet cycles—even winter hoarfrost and summer morning dew—sometimes adding more than one ring per year and adding radial growth at a rate up to 10 times faster than older trees. She also found that, in some cases, trees temporarily stop growing annual rings altogether, which is perhaps a genetic adaptation to periods of severe drought.

Post by: Bianca on May 16, 2009, 11:07:41 pm

And old trees, just like old humans, slow down considerably: Abdoun’s carbon-14 analysis showed that a tree in Wadi Tichouinet estimated to be 2200 years old, with a trunk radius of 63 centimeters (25"), has taken three-quarters of its life just to grow the last one-third of its width. A tree in Wadi InGharouhane is thought to have taken 1130 years to add just 25 centimeters (10") to its radius. These widely varied growth patterns, dependent upon microhabitat fluctuations, make it difficult to correlate rings in different trees to specific years. One tree may benefit from rain runoff coursing through the sandy soil it is rooted in, while a tree very nearby may miss even a quick sip.

Ahmad Hadrawi is a former park warden who now sells blankets in the Djanet marketplace. He retired in 2004 after spending 33 years in the field, much of it in tree protection. Over that time, he cared for his charges by reburying roots exposed by flooding, searching for new growth and collecting seeds for the National Forestry Research Center in Algiers. He got to know the trees almost as people.

“These trees need experts to help keep them alive,” he says. “They need people like me. Some are like babies, some are like old men, and some are still strong and can live by themselves.”

Hadrawi is correct to say that the trees need people—if only to protect them from tour groups scrounging for campfire wood. “The one we call Tin-Balalan,” he says, referring to the tarout with a 12-meter (48') girth in Wadi Amazar, “is, you know, the biggest in the world. It will not die anytime soon.” He is also correct about this, if we can assume that girth is relative to age. When last seen in February 2006, Tin-Balalan had a healthy crown and was drinking from a standing pool of water near its roots.

 Louis Werner

is a free-lance writer and filmmaker living in New York. He can be reached at 

 Kevin Bubriski

( is a documentary photographer who lives in southern Vermont.
His solo exhibition “Nepal Photographs: 1975–2005” is on view at the Visual Arts Center
of Union College in Schenectady, New York.

This article appeared on pages 32-39 of the September/October 2007 print edition of Saudi Aramco World.

Post by: Bianca on May 17, 2009, 08:45:22 am

Written by
Graham Chandler

Three reddish-brown giraffe images watch over Nick Brooks as he struggles, hunched over, to shovel sand from the rock shelter’s floor. Some 150 meters (500') above a sweeping, flat and desolate Western Sahara landscape, the burly environmental scientist is hoping these cliffs of Bou Dheir will reveal just when those animals roamed the plains. Three thousand years ago? Four thousand? Five thousand?

Today, only traces remain of the seasonal watercourse that until 5500 to 6000 years ago supported a landscape whose rich hunting we deduce from the abundance of animals in the area’s rock art.

Pinning down dates like these is essential to the study of human response to drastic alterations in climate. While many scientists believe climate change was responsible for the decline of such civilizations as the Mayan, a growing number, including Brooks, believes there’s also evidence that earlier global climate shifts actually spurred the beginnings of the world’s first civilizations.

For all of Earth’s history, the only constant about global climate has been its changes. For those climate-change episodes severe enough (and recent enough) to affect human survival, the response, in most cases, must have been to migrate and continue life in a new place, to adapt to new resources—or perish.

But one climatic episode in particular, a massive change during the fourth and early third millennium BC, shifted global rainfall patterns in many subtropical and temperate northern-hemisphere regions and caused severe desertification. Only that change—not any of the earlier ones—was immediately followed by the new human social arrangement we call “civilization.” Was that because the affected humans were larger groups that were forced to share limited resources, since they were boxed into refuges with no other place to go?

Post by: Bianca on May 17, 2009, 08:51:34 am

“If we define civilization as the emergence of large urban centers, labor specialization, bureaucracy, a high degree of social stratification with centralized authority, monumental architecture and writing —all these emerged as the result of increased competition for resources,” Brooks told me earlier. “What happens is increased territoriality, increased social pressures, technological innovations like irrigation, farming and herding, and concentration of political power.”

Beginning around 5500 years ago, Brooks says, humans developed civilizations in Egypt, Mesopotamia, the Indus Valley, north-central China and northern coastal Peru.

Like most other scientists, he shuns the idea of “climatic determinism,” but Brooks says the term illustrates that climatic and environmental change of the kind usually associated with the collapse
of civilizations also appears to have played a significant role in their emergence.

A research fellow at the Tyndall Centre for Climate Change in Norwich, England, Brooks directs the Western Sahara Project, and he is a special consultant on climate change adaptation for the United Nations Development Program.

He has spent considerable time on the topic in Libya, including investigating the role climate change played in the 2500-year-old Garamantes civilization of southwestern Libya, a region known as the Fezzan.

At the Sahara’s eastern end, other research is showing how desertification contributed to the emergence of the dynastic civilization of the Nile Valley in present-day Egypt and Sudan.

So, five years ago Brooks undertook study of the Sahara’s western end, long neglected in part because of politics and funding difficulties.

Post by: Bianca on May 17, 2009, 08:52:56 am

Standing Stones On Wadi Tifariti

Along the edges of Wadi Tifariti, archeologists have found evidence of a knapper’s site, where small blades and arrowheads were made.

“The area was pretty much unknown,” says Brooks. “Today the western Sahara is much more vegetated than the same latitudes further east. Certainly there is abundant evidence of water in the past, and, as in the rest of the Sahara, there are plenty of petroglyphs of large, humid-climate fauna.” He says the timing and speed of the Sahara desertification varied from place to place by as much as 1500 years, mediated by geography, topography, hydrogeology and the complexity of regional climatic systems. But most of the process, he says, was essentially complete by or soon after 3000 BC.

In the western Sahara, Brooks has found scads of evidence of human habitation—rock art, burial tumuli, enigmatic stone monuments and thousands of stone tools—but, unlike in the eastern Sahara, there are as yet no findings of civilizations here.

The plethora of cultural artifacts spurred Brooks to bring along this year archeologist Anne Pirie of the University of Reading. Focusing on the stone artifacts, she has identified small arrow or spear points similar to some found along the southern edge of the west and central Sahara that have been dated to between 6800 and 6500 BC, as well as much earlier Middle Paleolithic Levallois points that generally date to some 150,000 years ago.

There’s much more work to be done, but an exceedingly long human occupation is evident.

Post by: Bianca on May 17, 2009, 08:54:36 am

The noonday sun turns the desert sprawl below us into a shimmer, and the tender breeze at this relaxing spot tempts us to imagine prehistoric hunters whiling away their hours painting scenes on rock walls as they keep watch for prey in grassy savannah below.

On the walls, dramatic scenes of hunters armed with spears, aggressively moving in on herds, excite team member Maria Gaugnin, who’s here researching Saharan rock art for her doctoral degree at the University of Edinburgh.

Earlier, while researching in the Fezzan, “we found depictions of hippo and water buffalo,” she says—which could mean the climate was a lot wetter when they were painted. If similar animal images are here, and the art can be dated, she figures it would go a long way toward defining the time of the last wet period. “No one has seriously attempted to match the animals with their environments here in the Sahara,” she says.

Geological dating of the end of the last wet period here falls to another team member, Ann Mather, an earth scientist from the University of Plymouth who specializes in geomorphology and sedimentology. She avidly watches Brooks shoveling out the rock shelter, hoping she’ll be able to sample its lowest layer.

All the sand buildup that has reduced the shelter to a crawlspace would have occurred after the dry period began, and so, she reasons, if the lowest layers could be dated, it would help pin down when that drifting started—essentially, when the first wisps of sand blew in.

The team members, myself and three volunteers all arrived in the desert a week earlier on a night flight from Algiers to Tindouf, in southwestern Algeria, where we met with our guides and drivers, Osman and Sidi Ahmed.


They are Sahrawi (Tuaregs): indigenous Bedouins of Western Sahara.

They loaded us into two Toyota Land Cruisers and drove us to the white-walled Rabuni camp, where
we provisioned for our two-week foray. Rounding out the local team is our Sahrawi archeologist Hussein Mohammed Ali.

Post by: Bianca on May 17, 2009, 08:55:58 am



The early morning started us bouncing over desert roads and tracks, using the occasional shortcut across hard-packed sand, all to the lively strings of the Sahrawi tidinit playing on the stereo.

First stop was the site of Sluguilla, a previously discovered 26-kilometer (16-mi) stretch of rock engravings on flat stones.

Animal images range from giraffes to elephants and rhinos. “This is a place where people would have gathered in the past, exchanged stories, renewed old acquaintances, where the young would meet marriage partners, and so on,” says Brooks. 

Sluguilla hasn’t been dated. But clearly this entire area has been tramped by human feet for hundreds

of millennia.

Stone Age artifacts ranging from Acheulian hand axes—these can go back more than half a million years—to more recent tanged points of chert, the color of dark chocolate, lie scattered wherever we walk.

That evening, after a camel stew simmered on an acacia-wood campfire, Brooks relaxes over sweet green tea and tells us about his recent presentation on climate change, the Sahara and the origins of the earliest civilizations at the British Association Festival of Science.

“The Independent, Times, Telegraph, Scotsman and Irish Times were all very keen and prepared
articles on it,” he says.

Post by: Bianca on May 17, 2009, 08:57:17 am


That media interest grew because the idea that climate change could have led to the world’s first civilizations
has only recently been considered seriously by academics.

The Western Sahara Project members aren’t the only ones.

Daniel Sandweiss, professor of anthropology and quaternary and climate studies at the University of Maine, has
long been studying the cultural effects of climate changes along the northwestern coast
of South America. He too shuns use of the term “environmental determinism,” but he says there is a connection.

“Although environmental factors can move people in particular directions or force people to change in some way, you can’t absolutely predict direct causative links between environmental change and particular human outcomes,” Sandweiss tells me in a later interview. “But you can say that in periods
of particularly stressful change, people respond in some way. And archeologically we can look at the outcomes
and suggest that, in some cases, there is a link.”

Maybe behavior wasn’t determined by the climatic event, since there were many different choices how people
might deal with environmental change. “But it appears that part of the response to the changes in the climate
is what we see in the culture.”

Clearly not all climate change results in the rise of civilizations, he adds.

Conditions have to be right.

“If mobile hunter-gatherers living in a region where population density is low have a downturn in their particular territory, they could move somewhere else and continue the same lifestyle. Maybe you exploit different plants
and animals in the new location, but you’re still a hunter-gatherer or fisher. And you might some day come back
to your original area—you can move around.”

Post by: Bianca on May 17, 2009, 08:58:13 am

And here is where the difference lies.

Sandweiss says that if the new landscape fills up with too many people, the population becomes tied
to productive systems—such as irrigation agriculture—that require particular locales and infrastructure investments. “It becomes difficult for people to move around any more,” he says. “At some point there are simply too many people in the group, and too much population surrounding them, to allow them to move, and not enough new places to go.”

Sandweiss has found links with past El Niños (southward currents in the equatorial Pacific Ocean that influence weather and ecology) on the northwestern Peruvian coast. “El Niños may well have been as frequent 9000 years ago as now, but you didn’t get civilization then—because you’re talking about low population densities, hunter-gatherers, fishers who are extremely mobile. The landscape wasn’t filled
up, so they moved around.”

But he’s found that after a shift in the El Niño system about 5800 years ago that reduced natural sustenance at a time of higher population densities, traces of civilization first appeared. “We’re getting many of the things that most people consider part of civilization,” he says.

“Monumental construction, some early evidence for irrigation agriculture, apparently a social hierarchy in which a small number of people had more power and better living conditions than the majority of the people, and they were mobilizing labor to build those mounds.

So there’s a significant amount going on, arts of various kinds, and textiles. We’re beginning to get specialization of labor. So many of the things that we see in the standard definition of civilization are coalescing at this time.” 

Post by: Bianca on May 17, 2009, 08:59:07 am

It happened elsewhere, too, around the same time—about 5800 years ago.

When the rains failed decade after decade in Mesopotamia, small farming villages were devastated. Dense populations in a landscape with minimal carrying capacity forced the intensification of cropping and food storage—and the first appearance of bureaucracies to enforce equal distribution and protection.

Temples, city walls and other public works followed.

“The villages had coalesced into cities,” writes Brian Fagan, emeritus professor of anthropology at the University of California and one of the world’s leading archeological writers. “By 3100 BC, the southern cities had become the world’s first civilization. Ur became the hallmark of Mesopotamian civilization.”

In his recent book 'The Long Summer: How Climate Changed Civilization', he tells the story of human adaptation to the demands and challenges of ever-changing climate.

“Fagan might be more positive than I am about this innovation, casting it as a creative response to crisis,” says Brooks. “I see it more as a last resort, something that people found themselves doing without ever intending to—not that Fagan would argue that people ever planned to become civilized.”

Brooks says in Western Sahara there isn’t yet enough information to develop a narrative equivalent to that of Mesopotamia, but he wants to test the hypothesis that the social changes indicated by the arrival of cattle herding and the building of monuments paralleled, and were in large part a response to, changes in climate, especially desertification.

“In particular, we want to know whether these developments postdated those in the rest of the Sahara,” he says. “And if so, whether there is any evidence that western Sahara acted as a refuge
for those feeling aridity in parts of the Sahara to the east, where desertification was more advanced.”

Post by: Bianca on May 17, 2009, 09:00:18 am

Rock Art

The flats of Wadi Erni may have offered good fishing in the broad shallows, where rock art indicates humans may have been joined in the water by hippo.

After a night under a canopy of a million stars, we break camp and split into two groups—one will look for archeological sites and the other, with Mather, for alluvial fans and other datable geological formations.

To most reliably date events like ancient climate change, several indicators are best, to cross-check one against another.

Mather’s passion is the alluvial fans, which happen when water flows erode hillsides into flat valleys and the transported sediment forms large, delta-like structures. If these can be dated, they could indicate when the region last experienced regular heavy rainfalls. Before coming here, she pored over satellite photos to pinpoint fans that looked promising.

We bounce over rocks and soft sand with our GPS units at arm’s length out the window, looking for Mather’s fans. She looks at escarpment after escarpment. “Don’t know if these are alluvial,” she says. “They all look colluvial to me.” (Colluvial means they were built up through rockfall.) “We really need a place where there is some catchment area.”

When she finds the right one, it will be a prize.

“The newest sediments end up on the bottom of the fan and the oldest near the top,” she says. She wants to date the newest, because that’s the last time great volumes of water flowed here.

But she says she needs fans with well-defined layers deep enough to yield a sample that she could
date by optically-stimulated luminescence (OSL).

OSL is expensive—around a thousand dollars per sample—but it provides a pretty accurate measure of when the soil was last exposed to sunlight.

Post by: Bianca on May 17, 2009, 09:01:22 am

Alas, things often look different from a satellite.

None of the fans proves datable, so Mather turns to Plan B.

She says she can also date the end of the last wet period using sediments from a massive, dried-up lake bottom she spotted on her satellite map.

Off we bound, crossing the lake’s ancient shoreline, zigging and zagging over the cracked mud surface.

 We pass two parallel rows of stones, but they are not ancient: They are used for camel racing. At the old lake’s center, Mather declares, “Let’s dig a hole and see what’s under here.” We dig down about half a meter. “I would love to have a [natural] channel here,” says Mather, “so I could see the layers and tell how far we have to go down.” But we find no layers; neither the fans nor the lakes pan out.

In the late afternoon we rejoin the others, who have been exploring rock shelters eroded over thousands of millennia out of sandstone and mudstone seafloors.

Many are rich with rock art.

Gaugnin has found some indications of climate characteristics: white rhino images.

She points to one, explaining, “See here? It has a longer head and a slight hump on the shoulder and a wider mouth.” It’s the wide mouth that’s the clue: It means it’s more of a grazing animal than the black rhino, and grazing means it lived in a wetter climate than the black rhino likes.

We all pitch in, searching more walls for pictographs. Excitement abounds when new images are spotted. “Maria, I have what might be a hippo here,” Brooks calls out. “Not much of its head, but the body....” Gaugnin extricates herself from a tight cave corner and bounds over. “No, the legs are far too long,” she sighs. “It looks more like a gazelle with a fat rump.”

Post by: Bianca on May 17, 2009, 09:02:26 am

We all pitch in, searching more walls for pictographs.

Excitement abounds when new images are spotted.

“Maria, I have what might be a hippo here,” Brooks calls out. “Not much of its head, but the body....”

Gaugnin extricates herself from a tight cave corner and bounds over. “No, the legs are far too long,”
she sighs. “It looks more like a gazelle with a fat rump.”

Ostriches  near Wadi Ternit  may have appeared 5500 to 6000 years ago, and are also among the
fauna that is depicted in the area’s rock art. 

Next to the shelter with the white rhino image, Gaugnin has spotted a collapsed rock shelter with more rock paintings.

That gives her an idea: If the approximate date of the collapse could be determined, it would provide at least an end date—a date after which the painting must have been made.

Mather concurs.

“Let’s take a sample from the broken edge,” she says. “Here, this one follows the bedding plane.”

Clink, clink goes the hammer as a fist-sized chunk of sandstone and pyroxene falls loose. “We’ll use cosmogenic dating on this one,” she says, marking today’s date and GPS coordinates on the sample
with a felt pen.

Such are the trials and perils of dating western Saharan climate change.

It’s not as easy as picking up soil or rock samples and sending them off to the lab and waiting for the answer. It’s fraught with approximations, relative dates, post hoc dates, cross-checks and correlations.

Post by: Bianca on May 17, 2009, 09:05:49 am

Like the alluvial fans and lake bottoms, the Bou Dheir cave bottom doesn’t yield a good, datable sample either. But on the way back to Rabuni, Mather spots something on the roadside she hadn’t expected: a tufa, or carbonate, outcropping.

That usually indicates the remains of a freshwater lake.

She motions to driver Sidi Ahmed to stop, bounds out of the Toyota with her geologist’s hammer and pecks away at the chalk-like protrusion. She points to one good sign. “It’s quite filamentous,” she says, “so it’s likely not just formed by groundwater.” She takes a sample for dating, probably by way
of the uranium-thorium method—similar in principle to carbon-14 dating.

The valley of Lajuad has been dry year-round since desertification began. How did the people who

once made their livelihoods here respond when the rains no longer came?

Samples packed away, we bounce back across the arid result of Earth’s last great climate change.

What might happen this time around? The 130-country Intergovernmental Panel on Climate Change—co-winner of the Nobel Peace Prize—has mentioned that future responses to global warming could include the “migration of hundreds of millions of people from equatorial regions.”

Brooks isn’t surprised.

Our desert trip done, freshly shaved and sipping a café au lait in a splash of morning sun on the hotel patio in Algiers, he voices his hope that the latest climate change might be the dawn of a new, more responsible model of civilization.

Speaking of the old model, he says, “We’ve done our early development period, and our period of adolescent rebellion and irresponsibility. We’re now into post-adolescence.”

 Free-lance writer Graham Chandler (

received his doctorate in archeology from the University of London,
and he lives in Calgary, Alberta.

Post by: Qoais on December 17, 2009, 09:52:12 pm

Emi Koussi is a high pyroclastic shield volcano that lies at the south end of the Tibesti Mountains in the central Sahara of northern Chad. It is the highest mountain in Chad, and the highest in the Sahara. The volcano is one of several in the Tibesti massif, and reaches 3445 m in altitude, rising 2.3 km above the surrounding sandstone plains. The volcano is 60 by 80 km wide.
Two nested calderas cap the volcano, the outer one being about 12 by 15 km in size. Within it on the southeast side is a smaller caldera, about 2-3 km wide and 350 m deep. Numerous lava domes, cinder cones, maars, and lava flows are found both within the calderas and along the outer flanks of the shield.
Emi Koussi has been used as a close analog to the famous Martian volcano Elysium Mons. One of the most important morphological differences between volcanoes on Mars and Earth is the widespread furrowing of the surface due to flowing water on terrestrial volcanoes. The furrows are shallow valleys. Larger channels have a different origin. Major channels can be seen on volcanoes on both planets and indicate low points in caldera rims where lava spilled out of pre-collapse craters.