Climatic changes and cultural transformations in Farafra oasis , Egypt

Climatic changes and cultural transformations in Farafra oasis, Egypt Fekri Hassan A long-term international investigation of the geoarchaeology and prehistory of Farafra oasis in the Egyptian Sahara is reveal­ ing how a series of abrupt short-term climatic changes during the past 1 2,000 years restructured patterns of human settlement and subsistence. Increasing aridity eventually prompted Neolithic desert dwellers to migrate to and settle in the Nile valley.


F
amed for the natural beauty of its White Desert, Farafra oasis, once an inaccessible and mysterious place, has now become a favour ite stop on the tourist itinerary.It was in the 1970s, while exploring the pre history of Bahariya oasis,' that I ventured to the northern edge of the Farafra depres sion with Egyptian geologist El-Sayed Zghloul to examine a field of well devel oped calcite crystals at the pass of Naqb Abdulla.Some years later, in 1987, Bar bara Barich (University of Rome La Fig ure 1 The location of Farafra and other major oases of Egyp t's Western Desert, part of the eastern Sahara. Sapienza) and I started a programme of investigations at Farafra that still contin ues to yield new information on the pre history and Holocene geology of this part of the Egyptian Sahara. 2 Like other oases in the of the vast desert west of the Nile, Farafra is situated in a depression where water is available from natural springs and artesian wells.In the past, prehistoric peoples not only bene fi ted fr om the natural flow of ground water, but also at times from surface water in ephemeral lakes fed by local seasonal streams and runoff during phases of wetter climate.Having already worked in Siwa and Bahariya oases north ofFarafra (Fig. 1), I was confident when we began our inves tigations that we would find play a (ephem eral lake) deposits that bear witness to wetter episodes in the early and mid Holocene (Fig. 2).But we did not know how the record of past rainfall in Farafra oasis might compare in amount and sea sonality with that farther north.It was becoming clear that rainfall had increased from north to south, suggesting that its main source was related to the East Afri can-Indian Ocean summer-monsoon belt, and we wished to find out whether geo archaeological research in Farafra would confirm this hypothesis.
By then I had become particularly inter ested in the prehistory of Holocene popu lations in the Sahara, having realized early on that the virtual abandonment of the Egyptian Sahara coincided with the emer gence of Neolithic communities on the banks of the Nile.I wondered if Farafra would shed more light on this probable link between the Egyptian Sahara and the Neolithic communities of the Nile valley.Together with my Egyptian assistants, geologists Abdel Moneim Mahmoud and M. Abdel-Rahman Hemdan, then post graduate students at Ain Shams University and Cairo University respectively, I began a systematic exploration of the playa deposits ofthe Farafra depression.Barbara Barich was in charge of research on the cultural aspects of prehistoric settlements.Every year since then, a community ofltal ian and Egyptian academic nomads have set up camp at Farafra, and each year new discoveries help to resolve the geoarchaeo logical and archaeological puzzles of this intriguing oasis.They also provide new insights into the nature of climatic changes during the Holocene and the prehistoric transition in North Africa from hunting and gathering to herding and farming.

Origin of the Farafra depression
The current reputation of the White Desert as a major tourist attraction is attributable to the fairy-tale swarms of residual snow white chalk pedestals there, produced by karstic processes of limestone solution.This exotic, almost surreal, landscape is unique to Farafra because the chalk of Cre taceous age, exposed in the northern part of the oasis, is very susceptible to erosion.The Farafra depression was once thought to have been formed by wind erosion because of the prevalence of wind-blown (aeolian) sand deposits.However, we now know that, like other depressions in Egypt's Western Desert, it was formed in stages as a result of a dynamic interplay between fluvial and karstic processes, with inter ludes of aeolian activity, under changing climatic conditions since the Miocene epoch.3During the late Quaternary (the late Pleistocene and Holocene periods), fluvial activity was limited to occasional seasonal flow, and karstic solution was also limited.Wind action was pronounced during the Last Glacial Maximum (c.

21,000 calendar years ago) and again
Fi gure 2 We tter conditions during the Holocene are indicated by the rem ains of ephemeral lakes (playas) that dot the depressions of the Western Desert.Bahr Playa (sh own here) is one of the principal playas in the Farafra depression and has revealed evidence of human occupation.Th e rounded hillocks are erosional remnants of ancient lake beds.throughout the past 7000 years.Wind erosional features and aeolian sandsheets and dunes are no more than the final retouches on a more ancient landscape formed primarily as a result of water action.
The Farafra depression (Fig. 3) extends over an area of 10,000km2.It is bounded on the north, east and west by escarpments of the surrounding desert plateaux at 270-300m above sea level, with residual hills as high as 350m.The depression itself is rimmed by a series of rock slopes (pedi ments) at the bases ofthe escarpments, and playas occur close to the edges of the depression and in karstic basins on top of the plateaux.Aeolian sand deposits extend along the eastern margin of the depression in the Rajih-Bir Murr area.

Playa deposits and palaeoclimate
The sequence of playa deposits in the Farafra depression begins with an initial episode of wadi (stream-channel) activity, associated with ponds and ephemeral lakes, which formed Bir Nuss Old Playa (Fig. 3).This was followed by an erosional episode, which was in turn followed by a phase of playa deposition dated to c. 11,000 cal.BP (9650 bp uncalibrated).4This playa phase, which is well represented at Ain Raml (Fig. 3), was fed by wadi wash (occasional streamflow), as is indicated by lenses of fluvial sand and gravel.Follow ing another erosional episode, playa depo sition resumed.Deposits fr om this latter phase are represented at Bahr Playa in Wadi El-Obeiyid (Fig. 3) and date fr om c. 9000 to 8000 cal.BP (8080-7320 bp).The lower part of these sediments was formed when wadi flow was active, as is indicated by cross-laminated deposits of fluvial sand and gravel.5After c. 8000 cal.BP there was less fluvial activity, and most deposition was colluvial (i.e. the result of material being washed down slope), indicating that the climate was becoming progressively drier.White detrital deposits, dated to after c. 6800 cal.BP (6050 bp), show upward coars ening to granules and finally to large slabs of chalk overlying playa deposits, indi cating severe mechanical weathering.Temperature variations coupled with the freezing of moisture trapped in fissures were sufficient to produce angular lime stone blocks (Fig. 4).There is a shift from the yellowish hues of the main playa Fig ure 4 Angular detrital deposits formed fo llowing the main phase of playa form ation at Bohr Playa reveal that the shift to drier conditions by 6800 years ago was marked by extremely cold weather, sufficient to fre eze moisture trapped in rock fi ssures.deposits to the white colour of the detrital deposits at the end of the phase, indicating that by then temperature and rainfall were too low to mobilize iron oxides.Also, there is no evidence for the formation of salt or gypsum, which suggests that the water table dropped rapidly following the termi nation of playa deposition.
The youngest playa deposits in the sequence postdate the seventh millen nium cal.BP.At Bir Nuss (Fig. 3) they were mainly fed by discharges fr om springs and they are overlain by a layer of tu fa (spring deposited calcium carbonate), marking a moist cool phase.Other younger playa deposits are found at Rajih in the eastern part of the depression (Fig. 3).

Palaeoclimate, subsistence and cultural change
The occupational history ofFarafra oasis is closely linked to the changing climatic conditions and associated modifications of the desert landscape.Archaeological evidence suggests that hunter-gatherers who lived in transient encampments had inhabited the Farafra region since the early Holocene (eleventh millennium cal.BP).One of the main prehistoric settlements we have discovered -where excavations have revealed a complex depositional and occu pational history -consists of a series of slab-lined circular huts at the edge of a playa on a pediment leading to the El-Quss Abu Said plateau above Bahr Playa, in the area we named Hidden Valley (Figs 3, 5).The huts were placed at the edge of an ephemeral pond, fo rmed in a karstic depression.The stone slabs of the dwell ings are now embedded in a stratified sequence of playa and colluvial deposits.Although radiocarbon age determinations from the site span a range from greater than 8000 to 7000 cal.BP (7300 to 6200 bp), the main occupation, which includes formal hearths, dates to 7650 cal.BP (6900 bp).6 The hearths yielded evidence, in the form of charred plant remains, for the intensive utilization of wild sorghum and other wild grasses/ as well as bone fragments of domestic ovicaprids (sheep or goats).8Intercalated colluvial deposits above and below this occupation contain reworked older cultural material and provide anom alous (older) dates than might be expected from their stratigraphical position.9These colluvial deposits are particularly signifi cant because they are evidence of short term oscillations of severe storms alter nating with episodes of relative stability.Also, the climatic oscillations between 8000 and 6800 cal.BP appear to have been associated with a change in seasonality, with incursions of winter rain into the Farafra depression (as indicated by the presence of Mediterranean poppy seeds found in a hearth deposit).10Another of our main discoveries is a cavern in the cliff face that overlooks a high pediment above Wadi El-Obeiyid in Hidden Valley (Fig. 6).The entrance to the Fig ure 5 Th e fo undations of one of the stone-lined circular huts at Bahr Playa in Hidden Valley that date to between 8000 and 7000 years ago.El-Obeiyid cavern was filled with wind blown sand.Charcoal found at the base of the aeolian sequence (at 170 cm below the present surface) provided a date of c. 7850 ea!.BP (7000 bp).This is a significant dis covery because it pinpoints the onset of severe aridity when aeolian activity was re-intensified after the Last Glacial Maxi mum.A sample fr om the middle of the sequence at llOcm below the surface pro vided a date of c. 5200 ea!.BP (4460 bp).Pollen extracted from ancient sheep and goat droppings (coprolites) from the lower part of the aeolian stratigraphical unit (7850-5 200 ea!.BP) comes from plants typ ical of sandy plains and ridges that rise above the plains (cuestas).11We also made another significant discovery in the cav ern: rock art.Near the entrance, in the front and middle galleries of the cave, one can discern engravings of a kind ofmouflon, of an animal that resembles a pregnant (?) oryx, and of patterns of round depressions in what is described as a "lion fo ot" motif; also, in the rear gallery, there are many handprints on the wall and towards the ceiling (Figs 7, 8)Y

Regional cultural implications
The earliest evidence of sheep or goats at Farafra dates to 7650-7350 ea!.BP (6900-6500 bp), but there is no direct evidence of domestic cattle, which are present earlier farther south at Nabta Playa (Fig. 1)Y There is also evidence at Nabta of intensive utilization of sorghum and other seeds and tubers at 8900-8700 ea!.BP, pre-dating the sorghum found at Farafra by a millen nium.1 4 So far, only a few pot-sherds have been found at Farafra.
The advent of hyper-arid conditions at c. 8000 cal.BP, as indicated by the inten sification of aeolian activity at Farafra, was associated with a highly unstable climatic regime that eventually, by 6800 ea! BP, led to an actual reduction of rainfall.This pattern of climatic change at Farafra, which accords with evidence for a shift to arid conditions during this period all over North Africa, 15 stimulated many local population movements and cultural devel opments.It is also during this period that domestic sheep and goats were introduced into Egypt from Southwest Asia where they originated.16The evidence of goats and sheep at Farafra at c. 7650 ea!.BP com pares well with the other very early record of them in Africa (at c. 7850 ea!.BP) in the Egyptian Red Sea HillsY It is probable that by 7300 ea!.BP (6500 bp) intercultural contacts had intensified in the eastern Sahara as people ranged more widely across the landscape in response to greater climatic instability.This is suggested by similarities in the stone-tool assemblages found at Bashendi in the Dakhla oasis (Fig. 1) and Bahr Playa in Farafra.18 It is likely that ovicaprids, which are better adapted to desert condi tions than cattle are, would have been widely adopted at that time by eastern Fi gure 8 Han dprin ts on a wall in the rear chamber of the El Obyeiyid cavern, which is one of only three in Egyp t to reveal prehistoric rock art.
Saharan communities.No evidence of domestic cattle has been found at Farafra, but there is evidence of them at Dakhla in phase B of the Bashendi assemblages, which dates from 7300 to 6300 ea!.BP.This may represent the northernmost occur rence of domestic cattle in the Egyptian Sahara at this time, probably because the catchment areas of ephemeral lakes at Dakhla were larger than those at Farafra.19 Dakhla, which was at the junction of the expanding Mediterranean climatic regime and the retreating monsoonal fr ont, prob ably benefited from both winter and sum mer rains.Desert conditions at Farafra, even with occasional rain showers in win ter, were not suitable for herding cattle.Instead, sheep and goats were incor porated into a subsistence regime that emphasized the hunting of gazelle and other desert game animals as soon as they became available seasonally.However, there is no evidence that the adoption of domestic sheep and goats from Southwest Asia was accompanied by the introduction of domesticated wheat or barley, which also originated in Southwest Asia.More over, there is no evidence that wild cereal grasses indigenous to northern Africa, such as sorghum, were ever domesticated locally. 2 0 Desertification during the eighth mil lennium BP and thereafter would have encouraged some inhabitants of Farafra and Dakhla, as well as those farther south at Nabta, to expand their search for pas tures.Some may also have ventured into the Nile valley, perhaps initially for shorter visits and eventually to take up long-term residency.In the Nile valley, the earliest fo od-producing communities date to c. 6800 ea!.BP at Merimde Beni Salama, in the western Nile delta, and perhaps as early as 6400 ea!.BP at Badari in Middle Egypt (Fig. 1).These sites contain stone artefacts analogous to those from the east ern Sahara dating fr om 7600 to 7300 ea!.BP.21 Spells of severe hyper-aridity begin ning about 8000 ea!.BP could thus have encouraged some desert dwellers to settle on the banks of the Nile.However, the desert was not totally depopulated.The occupation at Rajih in Farafra and the late occupations at Dakhla suggest that the pre historic inhabitants of the oases struggled on until c. 5200 ea!.BP, when desert con ditions were already firmly established across North Africa.22

Conclusion
Our joint programme of geoarchaeological investigations and systematic archaeolog ical survey and excavation in Farafra has already yielded vital information concern ing both the changing Holocene climate and the prehistoric peoples of the eastern Sahara.Detailed microstratigraphical and sedimentological studies, coupled with other palaeoenvironmental analyses and many radiocarbon age determinations, are revealing how critical for human survival short-term climatic events were in the fickle desert environment.Our research in the Farafra depression has confirmed the supposition that rain was linked to north erly advances of the monsoonal front during the warm intervals of the Holocene, but the possibility that incursions of win ter rain from the Mediterranean occurred during the transitions from warm to cool climate requires a refinement of the cur rent model of climatic change in North Africa during the Holocene.

Fig ure 3
Fig ure3Th e Farafra depression, showing places mentioned in the text, the surro und ing desert plateaux, playas and other geomorphological fe atures.

Figure 6
Figure 6 Th e El Obeiyid cavern (arrow) is located in an escarpment cliff fa ce above Hi dden Va lley at Farafra ; Wa di El Obeiyid in the fo regro und.Dated deposits of win d blown sand in the entrance to the cave demonstrate that intensifi cation of aeolian activity began about 7850 years ago.

Figure 7
Figure 7 Rock engravings of an animal resembling a pregnant (?) oryx and a pattern of round depressions arranged in the "lion fo ot" motif, El Obeiyed cavern, Farafra.

Notes 1 .
F. A. Hassan, "Archaeological explora tions at Baharia Oasis and the West Delta, Egypt", Current Anthropology 20, 806, 1979.2. The term Holocene (literally "wholly recent") refers to the postglacial epoch of geological time, from about 11,500 calen dar (c.10,000 radiocarbon) years ago; together with the preceding two million years of the Pleistocene epoch it com prises the Quaternary era. 3. B. E. Barich & F. A. Hassan, "The Farafra Oasis archaeological project (Western Desert, Egypt)", Origini 13, 117-85, 1984-87.The Miocene epoch of geological time encompasses the period from approxi mately 24 to 5 million years ago.4. The relationship between calendar and radiocarbon years varies as one goes back in time.The difference between them is determined by reference to calibration curves that are obtained by radiocarbon dating samples of known calendric age.