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Map showing the locations of 1, 2) Susah Cave in northern Libya and nearby site Haua Fteah 11 , 3) Villars Cave 21 in France, 4) marine sediment core ODP 977 28 , 5) marine sediment core ODP 963 27 , 6) Levant with archaeological sites Kebara 44 and Boker Tachit 39 , 7) Pe?tera cu Oase 48 and 8) NGRIP ice core 24 . The map was created using the Geomar GMT-Maps web site (http://sfb574.geomar.de/gmt-maps.html).
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We present the first speleothem-derived central North Africa rainfall record for the last glacial period. The record reveals three main wet periods at 65-61 ka, 52.5-50.5 ka and 37.5-33 ka that lead obliquity maxima and precession minima. We find additional minor wet episodes that are synchronous with Greenland interstadials. Our results demonstrat...
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... in δ 18 O in speleothem calcite can be driven by a variety of effects 7 , for example, by changes of the rainwater source, moisture trajectories, ocean surface water composition (ice volume), amount effect, air tem- perature, and local effects in the cave such as drip rate, pCO 2 or cave air temperature 26 . The position of Susah cave (Fig. 1) suggests that the main precipitation source is the Mediterranean Sea, but Atlantic influences are also likely. In Fig. 3 as well as Mediterranean sea-surface temperature (SST) 28 . δ 18 O sea and SST show coherent patterns, con- sistent with a Mediterranean source for at least some rainfall at Susah cave. Changes in global ice volume ...
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... first-order effect on the high-frequency δ 18 O calcite changes recorded by SC-06-01 since ice volume-related source changes are not known on Dansgaard-Oeschger frequencies. However, comparison of the SC-06-01 δ 18 O calcite record with δ 18 O ice from NGRIP also indicates a high degree of correspondence, and the two records appear to be in-phase (Fig. 3 and SI, Fig. S9 and S10). This is true for both precessional and millennial timescales, regardless of the phasing with interstadials/stadials. Part of the SC-06-01 record is duplicated along a parallel secondary growth axis (Fig. 3), and this partial replication confirms the isotope pattern of SC-06-01. The correlation of the SC-06-01 and NGRIP data series ...
Citations
... It is likely, for example, that the greater spread in δ 18 O values which occurs in the Wadi Dabsa tufa dataset is a function of the impact of evaporation on surface waters, a process that is likely to be less significant in cave settings. However, despite this, it is argued that (Lisiecki and Raymo, 2005); (B) Red Sea Level (Grant and Rohling, 2014); (C) insolation at 30 • N; (D) sapropel timing in ODP 967 in Eastern Mediterranean (Kroon et al., 1998); (E) wet-dry index from ODP967 (Grant et al., 2017); (F) humidity trends in Arabia (solid line) and the Sahara (dotted line) (Drake et al., 2013); (G) Peqin and Soreq cave speleothem δ 18 O (Ayalon et al., 2002;Bar-Matthews et al., 1997, 2003Bar-Matthews and Ayalon, 2004); (H) speleothem growth phases, or dates with errors, Susah Cave, Libya (Hoffmann et al., 2016;Rogerson et al., 2019), Negev, Israel (Vaks et al., 2010(Vaks et al., , 2013; Wadi Sannur, Egypt (El-Shenawy et al., 2018); Hoti Cave Oman (Burns et al., 2001;Fleitmann et al., 2003aFleitmann et al., , 2003bFleitmann et al., , 2007Nicholson et al., 2020), Mukalla Cave Yemen Nicholson et al., 2020), also showing the Southern Arabian Humid Periods (SAHP) in green blocks (from Nicholson et al., 2020); (I) Arabian Peninsula palaeoloakes and fluvial systems, arranged by latitude -northern (Petraglia et al., 2012;Rosenberg et al., 2013;Jennings et al., 2015;Clark-Balzan et al., 2018;Parton et al., 2018;Groucutt et al., 2018Groucutt et al., , 2021 and southern (Rosenberg et al., 2011(Rosenberg et al., , 2012Hoffmann et al., 2015;Matter et al., 2015); (J) complied dates for tufa deposition (mostly U-Th and some 14 C ages) presented by latitude and longitude, including from the Daklah, Kharga, Kurkur, Farafra, Gebel el Digm, Dineigel and Dungul Oasis, and a variety of wadi sites in the eastern desert of Egypt and the Sinai Desert (Crombie et al., 1997;Sultan et al., 1997;Smith et al., 2004Smith et al., , 2007Kleindienst et al., 2008;Kleindienst et al., 2009;Brookes, 2010;Jimenez, 2014;Hamdan and Brook, 2015;Abotalib et al., 2019;Kele et al., 2021), and Wadi Dabsa, southwest Saudi Arabia (this study); (K) δD wax signatures in ocean core RC09-1066 (Tierney et al., 2017). ...
... There is widespread palaeoclimatological evidence indicating that the Sahara has experienced wetter periods in the past, with proliferation of vegetation, rivers and lakes into what is now desert [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] . The alternation of arid and humid phases and consequent dramatic environmental changes in this vast region forms a key biogeographic factor influencing species' distributions and evolution [17][18][19] . ...
The Sahara region has experienced periodic wet periods over the Quaternary and beyond. These North African Humid Periods (NAHPs) are astronomically paced by precession which controls the intensity of the African monsoon system. However, most climate models cannot reconcile the magnitude of these events and so the driving mechanisms remain poorly constrained. Here, we utilise a recently developed version of the HadCM3B coupled climate model that simulates 20 NAHPs over the past 800 kyr which have good agreement with NAHPs identified in proxy data. Our results show that precession determines NAHP pacing, but we identify that their amplitude is strongly linked to eccentricity via its control over ice sheet extent. During glacial periods, enhanced ice-albedo driven cooling suppresses NAHP amplitude at precession minima, when humid conditions would otherwise be expected. This highlights the importance of both precession and eccentricity, and the role of high latitude processes in determining the timing and amplitude of the NAHPs. This may have implications for the out of Africa dispersal of plants and animals throughout the Quaternary.
... 28-30). In North Africa, several different 'green Sahara' periods spanning marine isotope stages 5e, 4 and 3 are thought to have enabled human expansion inside and outside the continent and across an otherwise inhospitable desert [28][29][30][31][32] . Such a humid period could also have enabled an ancestral red fox population to colonize North Africa and expand to regions that were previously uninhabitable for the species, thus setting the stage for divergence from Eurasian red foxes and introgression with Rueppell's fox as subsequent climate change caused population isolation (Fig. 4a). ...
Elucidating the evolutionary process of animal adaptation to deserts is key to understanding adaptive responses to climate change. Here we generated 82 individual whole genomes of four fox species (genus Vulpes) inhabiting the Sahara Desert at different evolutionary times. We show that adaptation of new colonizing species to a hot arid environment has probably been facilitated by introgression and trans-species polymorphisms shared with older desert resident species, including a putatively adaptive 25 Mb genomic region. Scans for signatures of selection implicated genes affecting temperature perception, non-renal water loss and heat production in the recent adaptation of North African red foxes (Vulpes vulpes), after divergence from Eurasian populations approximately 78 thousand years ago. In the extreme desert specialists, Rueppell’s fox (V. rueppellii) and fennec (V. zerda), we identified repeated signatures of selection in genes affecting renal water homeostasis supported by gene expression and physiological differences. Our study provides insights into the mechanisms and genetic underpinnings of a natural experiment of repeated adaptation to extreme conditions.
... MIS3 was characterized by a resumption of humid conditions, 43 which were wetter compared to modern climate conditions, as shown by speleothem records from Libya. 48,49 However, MIS3 was not a Green Sahara period, 2,38 as rainfall was not sufficient to sustain ample vegetation. ...
The Sahara Desert, one of today’s most inhospitable environments, has known periods of enhanced precipitation that supported pre-historic humans. However, the Green Sahara timing and moisture sources are not well known due to limited paleoclimate information. Here, we present a multi-proxy (δ18O, δ13C, Δ17O, and trace elements) speleothem-based climate record from Northwest (NW) Africa. Our data document two Green Sahara periods during Marine Isotope Stage (MIS) 5a and the Early to Mid-Holocene. Consistency with paleoclimate records across North Africa highlights the east-west geographical extent of the Green Sahara, whereas millennial-scale North Atlantic cooling (Heinrich) events consistently resulted in drier conditions. We demonstrate that an increase in westerly-originating winter precipitation during MIS5a resulted in favorable environmental conditions. The comparison of paleoclimate data with local archaeological sequences highlights the abrupt climate deterioration and the decline in human density in NW Africa during the MIS5-4 transition, which suggests climate-forced dispersals of populations, with possible implications for pathways into Eurasia.
... There are, however, lacustrine sediments that contradict this, associated with glacial MIS 2, 4, 6 The results show coincidence with most interglacial MIS 1, 3, 5, 7 and 9 (red cells or areas), while others show considerable ages corresponding to glacial MIS 2, 4, and 6. These results give a way to the concept that supports the presence of regional pluvial or wet conditions interpreted due to the Atlantic westerlies (NAO) or rise in water table or possible shifting in ITCZ (Hoffmann et al., 2016;Revel et al., 2010) ( Fig. 40, Hoffmann et al., 2016). This suggests that other regional forces played a potential role in determining the regional climate and strengthening the role of North Atlantic (NAO) sea surface temperatures (SSTs) (Blome et al., 2012;Jimenez, 2014;Kele et al., 2021). ...
... There are, however, lacustrine sediments that contradict this, associated with glacial MIS 2, 4, 6 The results show coincidence with most interglacial MIS 1, 3, 5, 7 and 9 (red cells or areas), while others show considerable ages corresponding to glacial MIS 2, 4, and 6. These results give a way to the concept that supports the presence of regional pluvial or wet conditions interpreted due to the Atlantic westerlies (NAO) or rise in water table or possible shifting in ITCZ (Hoffmann et al., 2016;Revel et al., 2010) ( Fig. 40, Hoffmann et al., 2016). This suggests that other regional forces played a potential role in determining the regional climate and strengthening the role of North Atlantic (NAO) sea surface temperatures (SSTs) (Blome et al., 2012;Jimenez, 2014;Kele et al., 2021). ...
... Similar was the study of speleothem-derived central North Africa rainfall records for the last glacial period that revealed three main wet intervals at 65-61, 52.5-50.5 and 37.5-33 ka, and related to obliquity maxima and precession minima (Bosmans et al., 2015). In addition, North Atlantic (NAO) humid sources may explain the presence of several recorded pluvial intervals that belong to the glacial stages 2, 4, 6 and 8 (Hoffmann et al., 2016). In this concern, in order to understand Saharan paleoclimates and patterns of modern human migration, Abotalib et al. (2019) used 230 Th/ 234 U in dating to determine the age of thick accumulations of scarp and scarp-foot depression sediments. ...
The Quaternary sediments in Egypt record the interplay of several factors, the most important of which are marine, fluvial, terrestrial and climatic factors. According to the strength of each factor, the Egyptian territories are subdivided into several basins reflecting the potential depositional environments. The present review promotes the Quaternary sediments of the Nile Delta, the North Western coast, the Western Desert and the Red Sea and Gulf of Aqaba coasts as proxies for Quaternary paleoclimate. The Quaternary Nile Delta sediments clearly reflect the African monsoons and the associated Nile floods correlated with the Eastern Mediterranean and global marine isotope stratigraphy. The fossil records of both planktonic and benthonic foraminifera (Pl/Be) and their δ18O represent potential references to Marine Isotope Stages (MIS) and sea level changes. Pollen and spores, δ13C, C3 and C4 plants record paleovegetation cover, and thus paleoenvironments and paleoclimate. It has been globally agreed that the primary control of climate changes and the region’s hydrological cycle are the insolation-driven changes in the strength and shifting of the Intertropical Convergence Zone (ITCZ), and therefore the intensity and northward extent of the African Humid Period (AHP), non-excluding the Atlantic westerlies (NAO). Such conditions induced intervals of heavy rainfall in Egypt as well as the Nile Headwaters. In Egyptian Sahara, such heavy rains charged the groundwater and dissolved the Paleocene–Eocene carbonate leaving deposits of lacustrine and freshwater carbonate and other karstic landforms. These terrestrial deposits supported with the calibrated age dating are used as proxies for paleoclimate along the Sahara. At the Red Sea coast, the growth of coral reefs and deposition of thick fluvial gravels are used as proxies for climate and sea level changes, while the aeolianites and paleosols are the available proxies at the NW Mediterranean coast of Egypt. On the other hand, the increase in outflow of the River Nile led to stagnation of freshwater over the marine water and formation of sapropel layers in Eastern Mediterranean. The oxygen isotopes and age determination of the above-mentioned materials allow correlation with global climate conditions; however, such correlation is not always isochronic. The offsets are explained by the presence of regional driving forces overriding the global influences.KeywordsQuaternary geologyNile Delta sedimentsNW calcarenite ridgesRed sea coastEgyptian SaharaIsotope stratigraphyPaleoclimate
... Therefore, orbitally-paced humid conditions mark the W-Mediterranean region during MIS-3 and the Early Holocene. This is also suggested by speleothem-derived results that demonstrated rainfall enhancement during peaks in obliquity and/or precession minima in North Africa (Hoffmann et al., 2016;Rogerson et al., 2019). Increasing winter insolation at latitude 60°N relative to 33°N is prone to weaken the geostrophic gradient between Iceland Low and Azores High, leading to pervasive wetter conditions in W-Mediterranean (Hoffmann et al., 2016) akin to a negative NAO-like pattern (Wanner et al., 2001). ...
... This is also suggested by speleothem-derived results that demonstrated rainfall enhancement during peaks in obliquity and/or precession minima in North Africa (Hoffmann et al., 2016;Rogerson et al., 2019). Increasing winter insolation at latitude 60°N relative to 33°N is prone to weaken the geostrophic gradient between Iceland Low and Azores High, leading to pervasive wetter conditions in W-Mediterranean (Hoffmann et al., 2016) akin to a negative NAO-like pattern (Wanner et al., 2001). The general higher clastic-starvation of the upper sequence relative to the lower one during high lake levels is in sync with summer insolation at 33°N, winter insolation gradient between 60°N and 33°N, and biomass development in W-Mediterranean (Fig. 13); the upper sequence occurs during higher summer insolation, higher winter insolation gradient, and more enhanced biomass development relative to the lower sequence. ...
... The marl bed composing the upper interval reflects hydrological conditions between those giving way to the offshore mud and those conditioning the palustrine settings. Regionally, northern Africa during MIS-3 was experiencing increased effective rainfall that allowed speleothem growth in present-day arid areas, although intercepted by millennial timescale periods of isotopically less negative rainfall (Hoffmann et al., 2016;Rogerson et al., 2019) in sync with (i) North Atlantic cooling phases (Rasmussen et al., 2006(Rasmussen et al., , 2014Svensson et al., 2008), (ii) cooling phases of the Alboran Sea surface (lower SST, Fig. 13) (Cacho et al., 1999) and deep water (lower DWT; Cacho et al., 2006, their Fig. 4e), (iii) a decrease in vegetation density in the W-Mediterranean borderlands (Fletcher and Sánchez Goñi, 2008), and (iv) an increase in Saharan aeolian dust transport (Moreno et al., 2002;Bout-Roumazeilles et al., 2007) (Fig. 13). ...
Lacustrine settings constitute a unique environment that preserves detailed expressions of allocyclic signals such as those of climate and tectonics. Possible decryption of these signatures stems from careful scrutiny of the sed- imentation dynamics (temporary base-level variations), lake-level fluctuations (accommodation), and resulting strata bounding surfaces that are used to build a conventional sequence stratigraphic framework. However, due to discrepancies between marine, to which this approach has been initially dedicated, and lacustrine settings (es- pecially regarding the physical scale), deciphering climate from tectonic forcing becomes unwieldy in such inte- rior basins. The present work deals with this challenge and provides insights from a case study where lacustrine sedimentation occurs on a tectonically active half-graben within a key climate region (Lake Ifrah, Northwest Af- rica). We conducted conventional sedimentological and high-resolution sequence-stratigraphic analyses, inte- grated with palaeolimnological proxies (geochemical elements and ostracod species). Up to five facies models (accounting for lithological domination, wind-driven energy, and lake-level state) and three lowest rank T-R se- quences, deposited since the Marine Isotope Stage-3 (MIS-3), have been identified. Periods with sustained high lake levels appear to be mainly precession-paced (as during MIS-3 and the Early Holocene), although the role of obliquity is shown to influence the hydrological budget as well. Furthermore, sedimentation dynamics are shown to respond to millennial timescale climate variability associated with North Atlantic cooling events (Dansgaard- Oeschger stadials, Heinrich Events) and, interestingly, to enhanced Saharan winds during the deglacial period. On the other hand, tectonism had a rather instantaneous effect on lake level and sedimentation. Two tectonic pulses marking instantaneous differential hanging-wall subsidence have triggered a sharp drop in relative lake level, hence conditioning a forced regression.
We highlight the importance of the conventional high-resolution sequence stratigraphy in shaping our under- standing of the cyclic interplay between orbital/sub-orbital and tectonic forcings, so as the resulting sedimenta- tion dynamics and lake-level cycles in lacustrine settings. We stress the role of the forced regression concept and associated systems tract and bounding surfaces, as well as the importance of using ostracods and geochemical proxies to trace transgressions and cryptic surfaces with sequence-stratigraphic significance, such as the maxi- mum flooding surface, in lacustrine settings.
... Therefore, orbitally-paced humid conditions mark the W-Mediterranean region during MIS-3 and the Early Holocene. This is also suggested by speleothemderived results that demonstrated rainfall enhancement during peaks in obliquity and/or precession minima in North Africa (Hoffmann et al., 2016;Rogerson et al., 2019). Increasing winter insolation at latitude 60°N relative to 33°N is prone to weaken the geostrophic gradient between Iceland Low and Azores High, leading to pervasive wetter conditions in W-Mediterranean (Hoffmann et al., 2016) akin to a negative NAO-like pattern (Wanner et al., 2001). ...
... This is also suggested by speleothemderived results that demonstrated rainfall enhancement during peaks in obliquity and/or precession minima in North Africa (Hoffmann et al., 2016;Rogerson et al., 2019). Increasing winter insolation at latitude 60°N relative to 33°N is prone to weaken the geostrophic gradient between Iceland Low and Azores High, leading to pervasive wetter conditions in W-Mediterranean (Hoffmann et al., 2016) akin to a negative NAO-like pattern (Wanner et al., 2001). The general higher clastic-starvation of the upper sequence relative to the lower one during high lake levels is in sync with summer insolation at 33°N, winter insolation gradient between 60°N and 33°N, and biomass development in W-Mediterranean ( Fig. 13); the upper sequence occurs during higher summer insolation, higher winter insolation gradient, and more enhanced biomass development relative to the lower sequence. ...
... The marl bed composing the upper interval reflects hydrological conditions between those giving way to the offshore mud and those conditioning the palustrine settings. Regionally, northern Africa during MIS-3 was experiencing increased effective rainfall that allowed speleothem growth in present-day arid areas, although intercepted by millennial timescale periods of isotopically less negative rainfall (Hoffmann et al., 2016;Rogerson et al., 2019) in sync with (i) North Atlantic cooling phases (Rasmussen et al., 2006(Rasmussen et al., , 2014Svensson et al., 2008), (ii) cooling phases of the Alboran Sea surface (lower SST, Fig. 13) and deep water (lower DWT; Cacho et al., 2006, their Fig. 4e), (iii) a decrease in vegetation density in the W-Mediterranean borderlands (Fletcher and Sánchez Goñi, 2008), and (iv) an increase in Saharan aeolian dust transport ( Fig. 13). ...
... These proxies suggest that at least four humid periods may have punctuated the past ca. 65 ka (Hoffmann et al., 2016;Haynes et al., 1989;Kuper and Kröpelin). The last and most significant wet period, based on the interpretation of archeological sites associated with palaeo-zoological proxies and pollen records (Fig. 1.3;Ritchie and Haynes, 1987;Haynes et al., 1989;Kuper and Kröpelin, 2006;deMenocal et al., 2000), persisted from early to mid-Holocene time, and was termed the "African Humid Period" (AHP; ca.14. ...
... More recent gravels on what are now ridges in southern Egypt were deposited during late Quaternary (late Pleistocene and Holocene) wet climatic events, the so-called "Late Quaternary climate oscillation" (Fig. 2.15;Giegengack, 1968;Butzer and Hansen, Page | 56 1968;Zaki et al., 2020). During this time, there were abrupt changes in climate over the Sahara that led to sporadic heavy-rainfall events (e.g., Foucault and Stanley, 1989;Hoffmann et al., 2016). These wet and dry episodes caused the deposition, cementation, and inversion of these fluvial sediments. ...
... b) Detailed work on the nature, origin, and regional setting of the Oligocene fluvialdeltaic sediments and on polycrystalline gravel in the northern part of Fayum Depression and on the surface of Gallaba plain (e.g., Bown and Kraus, 1988;Issawi and Sallam, 2017). Giegengack, 1968;Foucault and Stanley, 1989;Issawi and McCauley, 1993;Omar and Steckler, 1995;Goudie, 2005;Hoffmann et al., 2016). PETM is the Paleocene-Eocene Thermal Maximum. ...
Ancient depositional rivers in arid regions (now expressed as ridges) host important repositories of past surface processes that can be used to infer past climates that sculpted the surface of both Earth and Mars. However, how frequent, how sustained, and under what climatic regimes these systems survived is hindered by the lack of field and laboratory observations that can help place quantitative constraints on their formation and preservation through time. Addressing these fundamental questions may improve our understanding of past climates and aid in the hunt for ancient habitability in these regions on Earth and Mars. Herein, I present five related attempts to quantify the formation and preservation of these ancient rivers through time via observations, measurements, and laboratory analyses. I first compiled new observations as well as those of previous studies; I concluded that, despite the assertation that fluvial ridges record long-lived fluvial activity, there is equivocal evidence for this idea in many fossil rivers (Chapter 2). Indeed, seven sites in Egypt have shown that these ridges likely record both sustained fluvial activity that led to the construction of large-scale paleo-drainage systems and snapshots of fluvial activity due to climatic oscillations in the late Quaternary (Chapter 3). Field observations from southern Egypt, coupled with carbon-14 and optically stimulated luminescence (OSL) dating, lend support to the conclusions that these fossil rivers formed due to high precipitation rates (55–80 mm/hr) and were more frequently active during the African Humid Period, rendering the area inhospitable for human settlements (Chapter 4). These terrestrial observations imply that martian fluvial ridge systems that record single-thread, short-distance source-to-sink courses may have formed due to transient drainage networks that were active over short durations of 10s to 100s of years over a few-thousand-year period (Chapter 5). A diverse array of fluvial systems within the Antoniadi crater on Mars may even record fluvial activity that lasted at least 10^3–10^6 years. These events occurred periodically under arid climates, thereby bolstering the hypothesis that episodic warming likely punctuated the planet’s early history (Chapter 6). Collectively, these findings place new quantitative constraints on the hydrology and climate of past Earth and Mars; these insights are critical for evaluating their habitability over space and time.
... In this regard, it must be noted that the history of spatial and temporal climatic variability of North Africa is complex and still debated, and that a strict association of glacial stages with wet conditions, and of interglacial stages with arid conditions, is too simplistic [64][65][66]. Palaeoclimatic records show several wet periods in North Africa during the last glacial period, supporting a scenario of expansion of Mediterranean habitats, but with at least one period of aridification at ⁓ 60 kya [64,65,67]. ...
The contribution of North Africa to the assembly of biodiversity within the Western Palaearctic is still poorly documented. Since the Miocene, multiple biotic exchanges occurred across the Strait of Gibraltar, underlying the high biogeographic affinity between the western European and African sides of the Mediterranean basin. We investigated the biogeographic and demographic dynamics of two large Mediterranean-adapted snakes across the Strait and assess their relevance to the origin and diversity patterns of current European and North African populations.
We inferred phylogeographic patterns and demographic history of M. monspessulanus and H. hippocrepis, based on range-wide multilocus data, combined with fossil data and species distribution modelling, under present and past bioclimatic envelopes. For both species we identified endemic lineages in the High Atlas Mountains (Morocco) and in eastern Iberia, suggesting their persistence in Europe during the Pleistocene. One lineage is shared between North Africa and southern Iberia and likely spread from the former to the latter during the sea-level low stand of the last glacial stage. During this period M. monspessulanus shows a sudden demographic expansion, associated with increased habitat suitability in North Africa. Lower habitat suitability is predicted for both species during interglacial stages, with suitable areas restricted to coastal and mountain ranges of Iberia and Morocco. Compiled fossil data for M. monspessulanus show a continuous fossil record in Iberia at least since the Pliocene and throughout the Pleistocene.
The previously proposed hypothesis of Pleistocene glacial extinction of both species in Europe is not supported based on genetic data, bioclimatic envelopes models, and the available fossil record. A model of range retraction to mountain refugia during arid periods and of glacial expansion (demographic and spatial) associated to an increase of Mediterranean habitats during glacial epochs emerges as a general pattern for mesic vertebrates in North Africa. Moreover, the phylogeographic pattern of H. hippocrepis conforms to a well-established biogeographic partition between western and eastern Maghreb.
... Late Quaternary climate oscillations in the eastern Sahara region have been identified, based on palaeo-discharge and sediment-load estimates of the Nile River, cave speleothems, dust fluxes, pollen records, groundwater-fed deposits, ancient watercourses, archeological evidence, and abrupt fluctuations of lake levels and lacustrine deposits ( Fig. 1A; Foucault and Stanley, 1989;Hoelzmann et al., 2000;Schuster et al., 2005;Hamdan and Brook, 2015;Hoffmann et al., 2016;Drake et al., 2011;Williams et al., 2015;Macklin et al., 2013Macklin et al., , 2015Woodward et al., 2015;Abotalib et al., 2016;Palchan and Torfstien, 2019;Manning and Timpson, 2014;Pausata et al., 2020). These proxies suggest that at least four humid periods may have punctuated the past ca. ...
... This humidity favored the growth of vegetation, the multiplication of active rivers and the development of perennial lakes, turning the arid Sahara into a savannah-like environment, and may have made the Nile Valley into a marshy and hazardous place, which is hypothesized to have triggered the migration of its riparian populations toward the deep Sahara across several hundreds of kilometers (Kuper and Kr€ opelin, 2006). To further test how (Ritchie and Haynes, 1987;Haynes et al., 1989), human occupation in the eastern Sahara (Kuper and Kr€ opelin, 2006), lacustrine deposits (Hoelzmann et al., 2000;Schuster et al., 2005;Ritchie and Haynes, 1987;Haynes et al., 1989, Damnati, 2000Kr€ opelin et al., 2008), groundwater-fed deposits (Hamdan and Brook, 2015;Hamdan and Lucarini, 2013;Abotalib et al., 2016), cave speleothems (Hoffmann et al., 2016;Fleitmann et al., 2011;Bar-Matthews et al., 2003), sediment cores (Palchan and Torfstien, 2019;Martrat et al., 2004;Wagner et al., 2019), and fluvial records Williams et al., 2015;Abotalib et al., 2019). (B) Digitally rendered mosaic of Landsat 8 image relief map showing the location of the study area and the distribution of the ancient rivers in southern Egypt. ...
... (C) Reconstructed phases of high Nile floods over the past 70 ka , and the cumulative probability density function plots of the dated Holocene fluvial sediments from the Nile's catchment and delta . Three wet periods (III, II, I) shaded by (light gray) were recorded by speleothems in Susah Cave, Libya (Hoffmann et al., 2016). The AHP is in a dark gray area (deMenocal et al., 2000). ...
During the Quaternary period, the eastern Sahara's hydroclimate oscillated between wet and dry intervals. These oscillations caused drastic changes in precipitation rates, often associated with ancient human migrations. In particular, significant migration of riparian populations from the Nile Valley to the west and northwestward of the Sahara occurred during the African Humid Period (AHP), an episode of increased monsoons, which characterized North Africa in response to increasing insolation. Several fossil rivers, now preserved as ridges throughout southern Egypt due to their floodplains' deflation, contain archeological artifacts and thus represent a potentially important record of fluvial activity during this episode of past human dynamics and environmental change. Here we present 14C and Optically Stimulated Luminescence (OSL) ages of sediments preserved in these palaeorivers, which cluster within the AHP and are thus consistent with increased fluvial activity during this distinct humid period. Palaeohydraulic reconstructions based on grain size, channel geometry, and drainage area suggest typical precipitation intensities of 55–80 mm/h during sediment transport events. Given previous annual rainfall estimates, these hydrologic conditions may have lasted, or occurred, during the AHP up to 3–4 times more frequently than before and after this period. Such intense fluvial activity is consistent with monsoon intensification and may have rendered the area inhospitable for human settlements, congruent with population migration out of the Nile Valley during the AHP. These findings highlight links between past human ecodynamics and environmental signals, providing a concrete narrative of human population response to warming with potential echo in the current situation.
