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Cited by 334Geology and Paleoclimatology ResearchPleistocene-Era Hominins and ArchaeologySoil and Environmental Studies

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Dynamics of Green Sahara Periods and Their Role in Hominin Evolution

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Larrasoaña, Juan C., Roberts, Andrew P., Rohling, Eelco J.·2013·PLoS ONE
DOI 10.1371/journal.pone.0076514PMC PMC3797788
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Abstract

Astronomically forced insolation changes have driven monsoon dynamics and recurrent humid episodes in North Africa, resulting in green Sahara Periods (GSPs) with savannah expansion throughout most of the desert. Despite their potential for expanding the area of prime hominin habitats and favouring out-of-Africa dispersals, GSPs have not been incorporated into the narrative of hominin evolution due to poor knowledge of their timing, dynamics and landscape composition at evolutionary timescales. We present a compilation of continental and marine paleoenvironmental records from within and around North Africa, which enables identification of over 230 GSPs within the last 8 million years. By combining the main climatological determinants of woody cover in tropical Africa with paleoenvironmental and paleoclimatic data for representative (Holocene and Eemian) GSPs, we estimate precipitation regimes and habitat distributions during GSPs. Their chronology is consistent with the ages of Saharan archeological and fossil hominin sites. Each GSP took 2-3 kyr to develop, peaked over 4-8 kyr, biogeographically connected the African tropics to African and Eurasian mid latitudes, and ended within 2-3 kyr, which resulted in rapid habitat fragmentation. We argue that the well-dated succession of GSPs presented here may have played an important role in migration and evolution of hominins.

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Figures

Figure 1 Map of North Africa with relevant meteorological and physiographic features. Meteorological features are after ref. [4], the location of normal faults in the East African Rift System (EARS) is after ref. [88], and the extents of the Nile and North African margin basins are after refs. [8], [78]–[80]. The map includes the present-day distribution (grey shading) and occurrence of fossil remains (star) of chimpanzees (Pan) [69], and the locations of records mentioned in the text. WAM: West African monsoon; EAM: East African monsoon; ITCZ: Inter-tropical convergence zone.
Figure 1 Map of North Africa with relevant meteorological and physiographic features. Meteorological features are after ref. [4], the location of normal faults in the East African Rift System (EARS) is after ref. [88], and the extents of the Nile and North African margin basins are after refs. [8], [78]–[80]. The map includes the present-day distribution (grey shading) and occurrence of fossil remains (star) of chimpanzees (Pan) [69], and the locations of records mentioned in the text. WAM: West African monsoon; EAM: East African monsoon; ITCZ: Inter-tropical convergence zone.CC BY · PubMed Central
Figure 2 Present day meteorology and vegetation in North Africa. (a) Latitudinal distribution of present-day vegetation belts (MED.: Mediterranean and sub-Mediterranean; DES.: desert; GBT: grassland, bushland and thicket; WOO: woodland; FMT: forest mosaics and transitions; FOR.: rain forest) [60], and mean annual precipitation (MAP) and meteorological elements [3], [4], [59] projected onto a cross-section along the eastern Sahara (dark N-S line in b). (b) Map of the main physiographic and tectonic [88], [97] elements. Coloured vegetation belts are based on a structural classification of vegetation (indicating percentages of woody cover: %wc) using MAP values and main climatological determinants on tropical African biomes [56].
Figure 2 Present day meteorology and vegetation in North Africa. (a) Latitudinal distribution of present-day vegetation belts (MED.: Mediterranean and sub-Mediterranean; DES.: desert; GBT: grassland, bushland and thicket; WOO: woodland; FMT: forest mosaics and transitions; FOR.: rain forest) [60], and mean annual precipitation (MAP) and meteorological elements [3], [4], [59] projected onto a cross-section along the eastern Sahara (dark N-S line in b). (b) Map of the main physiographic and tectonic [88], [97] elements. Coloured vegetation belts are based on a structural classification of vegetation (indicating percentages of woody cover: %wc) using MAP values and main climatological determinants on tropical African biomes [56].CC BY · PubMed Central
Figure 3 Late Pleistocene-Holocene climate variability in North Africa. (a) Histograms of ages of continental sediments indicative of wetter conditions at different latitudinal bands across North Africa between 0 and 16 kyr BP [6], plotted with marine records that reveal North African climate variability at comparable latitudes (sea surface salinity (SSS) from core MD03-2707 [61], humidity index from core GeoB7920-2 [62] and sapropel record from ODP Leg 160 [63], [64] and summer insolation curves (June, July, August; JJA) at 10°, 20° and 25°N [107]. Bars indicate the 5 and 95 percentiles around the median of the histograms. (b) Histogram of ages of continental sediments indicative of wetter conditions throughout the Sahara between 30 and 150 kyr BP, with SSS from core MD03-2707 [61], humidity index from core GeoB7920-2 [62] and the sapropel record from core ODP Leg 160 [63] and their relevant summer insolation curves [107]. The chronology of sapropels is after ref. [65]. (c) Histogram of ages of continental sediments indicative of wetter conditions throughout the Sahara between 150 and 500 kyr BP, plotted with the eastern Mediterranean sapropel record from ODP Leg 160 [63] and summer insolation at 25°N [107]. Unlabelled sapropels correspond to those erased by post-depositional oxidation [63].
Figure 3 Late Pleistocene-Holocene climate variability in North Africa. (a) Histograms of ages of continental sediments indicative of wetter conditions at different latitudinal bands across North Africa between 0 and 16 kyr BP [6], plotted with marine records that reveal North African climate variability at comparable latitudes (sea surface salinity (SSS) from core MD03-2707 [61], humidity index from core GeoB7920-2 [62] and sapropel record from ODP Leg 160 [63], [64] and summer insolation curves (June, July, August; JJA) at 10°, 20° and 25°N [107]. Bars indicate the 5 and 95 percentiles around the median of the histograms. (b) Histogram of ages of continental sediments indicative of wetter conditions throughout the Sahara between 30 and 150 kyr BP, with SSS from core MD03-2707 [61], humidity index from core GeoB7920-2 [62] and the sapropel record from core ODP Leg 160 [63] and their relevant summer insolation curves [107]. The chronology of sapropels is after ref. [65]. (c) Histogram of ages of continental sediments indicative of wetter conditions throughout the Sahara between 150 and 500 kyr BP, plotted with the eastern Mediterranean sapropel record from ODP Leg 160 [63] and summer insolation at 25°N [107]. Unlabelled sapropels correspond to those erased by post-depositional oxidation [63].CC BY · PubMed Central
Figure 4 Reconstruction of North African vegetation during past green Sahara periods. (a) Estimated and reconstructed MAP for the Holocene GSP (6–10 kyr BP) projected onto a cross-section along the eastern Sahara (left panel) and map view of reconstructed MAP, vegetation and physiographic elements [7], [8], [11], [45] (right panel). (b) Estimated and reconstructed MAP for the Eemian GSP (122–128 kyr BP) projected onto a cross-section along the eastern Sahara (left panel) and map view of reconstructed MAP, vegetation and physiographic elements [14], [15], [44], [45] (right panel).
Figure 4 Reconstruction of North African vegetation during past green Sahara periods. (a) Estimated and reconstructed MAP for the Holocene GSP (6–10 kyr BP) projected onto a cross-section along the eastern Sahara (left panel) and map view of reconstructed MAP, vegetation and physiographic elements [7], [8], [11], [45] (right panel). (b) Estimated and reconstructed MAP for the Eemian GSP (122–128 kyr BP) projected onto a cross-section along the eastern Sahara (left panel) and map view of reconstructed MAP, vegetation and physiographic elements [14], [15], [44], [45] (right panel).CC BY · PubMed Central
Figure 5 Saharan climate and hominin occupation 8 Ma to present. (a) Chronology of global climate transitions [88] (NHG: northern hemisphere glaciation). (b) Chronology of East Africa Rift System (EARS) lake periods [88]. Formation of large lakes was prevented by the lack of full-graben basin morphologies before 5 Ma. Vertical shaded bars indicate periods with large, deep, freshwater lakes. (c) Chronology of lacustrine, peri-lacustrine and eolian sediments in the North Chad Basin [48] plotted with earliest evidence for mixed C3/C4 and pure C4 mammal diets in the basin [96]. (d) Chronology of Saharan hominin occupation sites [11], [12], [14], [47], [48], [50]. (e) Variations in summer insolation (June, July, August; JJA) at 25°N and eccentricity back to 8 Ma [107]. (f) Composite eastern Mediterranean sapropel record from ODP Leg 160 sites [63] and land sections at Gibliscemi, Metochia, Kastelli and Faneromeni [85], [86] (red bars indicate oxidized sapropels). (g) Green Sahara periods back to 8 Ma inferred from the eastern Mediterranean sapropel record.
Figure 5 Saharan climate and hominin occupation 8 Ma to present. (a) Chronology of global climate transitions [88] (NHG: northern hemisphere glaciation). (b) Chronology of East Africa Rift System (EARS) lake periods [88]. Formation of large lakes was prevented by the lack of full-graben basin morphologies before 5 Ma. Vertical shaded bars indicate periods with large, deep, freshwater lakes. (c) Chronology of lacustrine, peri-lacustrine and eolian sediments in the North Chad Basin [48] plotted with earliest evidence for mixed C3/C4 and pure C4 mammal diets in the basin [96]. (d) Chronology of Saharan hominin occupation sites [11], [12], [14], [47], [48], [50]. (e) Variations in summer insolation (June, July, August; JJA) at 25°N and eccentricity back to 8 Ma [107]. (f) Composite eastern Mediterranean sapropel record from ODP Leg 160 sites [63] and land sections at Gibliscemi, Metochia, Kastelli and Faneromeni [85], [86] (red bars indicate oxidized sapropels). (g) Green Sahara periods back to 8 Ma inferred from the eastern Mediterranean sapropel record.CC BY · PubMed Central

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Citations

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Research works printed but not linked: 7

  1. N Petit-Maire, 1986, Palaeoclimates in the Sahara of Mali. A multidisciplinary study, Episodes, 9, 7
  2. C Causse, 1988, The last Pleistocene humid phase in the Western Sahara, dated to about 80–100 ka, C R Acad Sci Paris, 306, 1459
  3. Wendorf F, Schild R, Close AE, Schwarcz HP, Miller GH, <etal>et al</etal>.. (1994) A chronology for the middle and late Pleistocene wet episodes in the Eastern Sahara. In: Bar-Yosef O, Kra R, eds. Egypt During the Last Interglacial: the Middle Paleolithic of Bir Tarwafi and Bir Sahara East. New York: Plenum Press. 147–168.
  4. N Petit Maire, 1994, A last interglacial palaeolake in the hyperarid Sahara of Mali, 23°N, C R Acad Sci Paris, 319, 805
  5. Kleindienst MR, Schwarcz HP, Nicoll K, Churcher CS, Frizano J, <etal>et al</etal>.. (2008) Water in the desert: first report on uranium-series dating of Caton-Thompson’s and Gardner’s “classic” Pleistocene sequence at Refuf Pass, Kharga Oasis. In: Wiseman MF, ed. Oasis Papers II: Proceedings of the Second Dakhleh Oasis Project Research Seminar. Oxford: Oxbow Books. 25–54.
  6. MAE Hamdam, 2000, Quaternary travertines of Wadis Abu Had-Dib Area, eastern desert, Egypt: palaeoenvironment through field, sedimentology, age and isotopic study, Sedimentology of Egypt, 8, 49
  7. PM McHugh, 1988, Acheulian sites along the “radar rivers”, J Field Archaeol, 15, 361

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Metadata

Authors
Larrasoaña, J. C., Roberts, A. P., & Rohling, E. J.
Affiliations
Australian National University (AU)
Corresponding author
Larrasoaña, Juan C.
ORCID
Venue
PLoS ONE
Publisher
Public Library of Science (PLoS)
Published
2013-10-16
Volume
8
Issue
10
Pages
e76514
ISSN
1932-6203 (ISSN-L)
DOI
10.1371/journal.pone.0076514
PMC
PMC3797788
OpenAlex
W2018031694
Cited by
334
References
104
Citations by year
2026: 17 · 2025: 29 · 2024: 35 · 2023: 43 · 2022: 40 · 2021: 38 · 2020: 31 · 2019: 20 · 2018: 22 · 2017: 21 · 2016: 14 · 2015: 16 · 2014: 6 · 2013: 2
FWCI
8.25
Type
journal article
Language
en
Open access
Licence
Locations
  • PLoS ONE (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • ePrints Soton (University of Southampton) (acceptedVersion)
  • ANU Open Research (Australian National University) (submittedVersion, other-oa)
  • Institutional Archive of Ifremer (French Research Institute for Exploitation of the Sea) (submittedVersion, other-oa)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Zaguan (Universidad de Zaragoza) (submittedVersion, cc-by)
Funders
Natural Environment Research Council (NE/I009906/1, NE/H004424/1, NE/E01531X/1)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Geology and Paleoclimatology Research
  • Social Sciences › Anthropology › Pleistocene-Era Hominins and Archaeology
  • Life Sciences › Agricultural and Biological Sciences › Soil Science › Soil and Environmental Studies
Keywords
hominin evolution, monsoon dynamics, insolation forcing, savannah expansion, paleoenvironmental records, paleoclimate, woody cover, precipitation regime, habitat fragmentation, dispersal out of Africa, Holocene, Last Interglacial, North Africa, paleoecology
MeSH terms
Africa, Northern, Animals, Climate, Biological Evolution, Rain, Time Factors, Tropical Climate, Hominidae, Ecosystem, Phylogeography

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