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Pleistocene drivers of Northwest African hydroclimate and vegetation. Nat Commun 2022; 13:3552. [PMID: 35729104 PMCID: PMC9213457 DOI: 10.1038/s41467-022-31120-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 06/06/2022] [Indexed: 11/09/2022] Open
Abstract
Savanna ecosystems were the landscapes for human evolution and are vital to modern Sub-Saharan African food security, yet the fundamental drivers of climate and ecology in these ecosystems remain unclear. Here we generate plant-wax isotope and dust flux records to explore the mechanistic drivers of the Northwest African monsoon, and to assess ecosystem responses to changes in monsoon rainfall and atmospheric pCO2. We show that monsoon rainfall is controlled by low-latitude insolation gradients and that while increases in precipitation are associated with expansion of grasslands into desert landscapes, changes in pCO2 predominantly drive the C3/C4 composition of savanna ecosystems.
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Lupien RL, Russell JM, Pearson EJ, Castañeda IS, Asrat A, Foerster V, Lamb HF, Roberts HM, Schäbitz F, Trauth MH, Beck CC, Feibel CS, Cohen AS. Orbital controls on eastern African hydroclimate in the Pleistocene. Sci Rep 2022; 12:3170. [PMID: 35210479 PMCID: PMC8873222 DOI: 10.1038/s41598-022-06826-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 02/07/2022] [Indexed: 11/24/2022] Open
Abstract
Understanding eastern African paleoclimate is critical for contextualizing early human evolution, adaptation, and dispersal, yet Pleistocene climate of this region and its governing mechanisms remain poorly understood due to the lack of long, orbitally-resolved, terrestrial paleoclimate records. Here we present leaf wax hydrogen isotope records of rainfall from paleolake sediment cores from key time windows that resolve long-term trends, variations, and high-latitude effects on tropical African precipitation. Eastern African rainfall was dominantly controlled by variations in low-latitude summer insolation during most of the early and middle Pleistocene, with little evidence that glacial–interglacial cycles impacted rainfall until the late Pleistocene. We observe the influence of high-latitude-driven climate processes emerging from the last interglacial (Marine Isotope Stage 5) to the present, an interval when glacial–interglacial cycles were strong and insolation forcing was weak. Our results demonstrate a variable response of eastern African rainfall to low-latitude insolation forcing and high-latitude-driven climate change, likely related to the relative strengths of these forcings through time and a threshold in monsoon sensitivity. We observe little difference in mean rainfall between the early, middle, and late Pleistocene, which suggests that orbitally-driven climate variations likely played a more significant role than gradual change in the relationship between early humans and their environment.
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Affiliation(s)
- Rachel L Lupien
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, 02912, USA. .,Biology and Paleo Environment, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, 10964, USA.
| | - James M Russell
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, 02912, USA
| | - Emma J Pearson
- School of Geography, Politics & Sociology, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK
| | - Isla S Castañeda
- Department of Geosciences, University of Massachusetts Amherst, Amherst, MA, 01003, USA
| | - Asfawossen Asrat
- Department of Mining and Geological Engineering, Botswana International University of Science and Technology, Private Bag 16, Palapye, Botswana.,School of Earth Science, Addis Ababa University, Addis Ababa, Ethiopia
| | - Verena Foerster
- Institute for Geography Education, University of Cologne, 50931, Cologne, Germany
| | - Henry F Lamb
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK.,Botany Department, Trinity College Dublin, Dublin 2, Ireland
| | - Helen M Roberts
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK
| | - Frank Schäbitz
- Institute for Geography Education, University of Cologne, 50931, Cologne, Germany
| | - Martin H Trauth
- Institute of Geosciences, University of Potsdam, 14476, Potsdam, Germany
| | - Catherine C Beck
- Geosciences Department, Hamilton College, Clinton, NY, 13323, USA
| | - Craig S Feibel
- Department of Earth and Planetary Sciences, Rutgers University, Piscataway, NJ, 08854, USA
| | - Andrew S Cohen
- Department of Geosciences, University of Arizona, Tucson, AZ, 85721, USA
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Cruaud A, Lehrter V, Genson G, Rasplus JY, Depaquit J. Evolution, systematics and historical biogeography of sand flies of the subgenus Paraphlebotomus (Diptera, Psychodidae, Phlebotomus) inferred using restriction-site associated DNA markers. PLoS Negl Trop Dis 2021; 15:e0009479. [PMID: 34280193 PMCID: PMC8425549 DOI: 10.1371/journal.pntd.0009479] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 09/08/2021] [Accepted: 05/15/2021] [Indexed: 11/19/2022] Open
Abstract
Phlebotomine sand flies are the main natural vectors of Leishmania, which cause visceral and tegumentary tropical diseases worldwide. However, their taxonomy and evolutionary history remain poorly studied. Indeed, as for many human disease vectors, their small size is a challenge for morphological and molecular works. Here, we successfully amplified unbiased copies of whole genome to sequence thousands of restriction-site associated DNA (RAD) markers from single specimens of phlebotomines. RAD markers were used to infer a fully resolved phylogeny of the subgenus Paraphlebotomus (11 species + 5 outgroups, 32 specimens). The subgenus was not recovered as monophyletic and we describe a new subgenus Artemievus subg. nov. Depaquit for Phlebotomus alexandri. We also confirm the validity of Ph. riouxi which is reinstated as valid species. Our analyses suggest that Paraphlebotomus sensu nov. originated ca 12.9-8.5 Ma and was possibly largely distributed from peri-Mediterranean to Irano-Turanian regions. Its biogeographical history can be summarized into three phases: i) a first split between Ph. riouxi + Ph. chabaudi and other species that may have resulted from the rise of the Saharan belt ca 8.5 Ma; ii) a Messinian vicariant event (7.3-5.3 Ma) during which the prolonged drought could have resulted in the divergence of main lineages; iii) a recent radiation event (3-2 Ma) that correspond to cycles of wet and dry periods in the Middle East and the East African subregions during the Pleistocene. Interestingly these cycles are also hypothetical drivers of the diversification of rodents, in the burrows of which Paraphlebotomus larvae develop. By meeting the challenge of sequencing pangenomics markers from single, minute phlebotomines, this work opens new avenues for improving our understanding of the epidemiology of leishmaniases and possibly other human diseases transmitted by arthropod vectors.
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Affiliation(s)
- Astrid Cruaud
- CBGP, INRAE, CIRAD, IRD, Montpellier SupAgro, Montpellier, Univ Montpellier, France
| | - Véronique Lehrter
- Université de Reims Champagne Ardenne, ESCAPE EA7510, USC ANSES VECPAR, SFR Cap Santé, UFR de Pharmacie, Reims, France
| | - Guenaëlle Genson
- CBGP, INRAE, CIRAD, IRD, Montpellier SupAgro, Montpellier, Univ Montpellier, France
| | - Jean-Yves Rasplus
- CBGP, INRAE, CIRAD, IRD, Montpellier SupAgro, Montpellier, Univ Montpellier, France
| | - Jérôme Depaquit
- Université de Reims Champagne Ardenne, ESCAPE EA7510, USC ANSES VECPAR, SFR Cap Santé, UFR de Pharmacie, Reims, France
- * E-mail:
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4
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Lupien RL, Russell JM, Subramanian A, Kinyanjui R, Beverly EJ, Uno KT, de Menocal P, Dommain R, Potts R. Eastern African environmental variation and its role in the evolution and cultural change of Homo over the last 1 million years. J Hum Evol 2021; 157:103028. [PMID: 34216947 DOI: 10.1016/j.jhevol.2021.103028] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 05/20/2021] [Accepted: 05/20/2021] [Indexed: 10/21/2022]
Abstract
Characterizing eastern African environmental variability on orbital timescales is crucial to evaluating the hominin evolutionary response to past climate changes. However, there is a dearth of high-resolution, well-dated records of ecosystem dynamics from eastern Africa that cover long time intervals. In the last 1 Myr, there were significant anatomical and cultural developments in Homo, including the origin of Homo sapiens. There were also major changes in global climatic boundary conditions that may have affected eastern African environments, yet potential linkages remain poorly understood. We developed carbon isotopic records from plant waxes (δ13Cwax) and bulk organic matter (δ13COM) from a well-dated sediment core spanning the last ∼1 Myr extracted from the Koora Basin, located south of the Olorgesailie Basin, in the southern Kenya rift. Our record characterizes the climatic and environmental context for evolutionary events and technological advances recorded in the adjacent Olorgesailie Basin, such as the transition from Acheulean to Middle Stone Age tools by 320 ka. A significant shift toward more C4-dominated ecosystems and arid conditions occurred near the end of the mid-Pleistocene Transition, which indicates a link between equatorial eastern African and high-latitude northern hemisphere climate. Environmental variability increases throughout the mid- to late-Pleistocene, superimposed by precession-paced packets of variability modulated by eccentricity. An interval of particularly high-amplitude climate and environmental variability occurred from ∼275 ka to ∼180 ka, synchronous with evidence for the first H. sapiens fossils in eastern Africa. These results support the 'variability selection hypothesis' that increased environmental variability selected for adaptable traits, behaviors, and technology in our hominin ancestors.
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Affiliation(s)
- Rachel L Lupien
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02906, USA; Division of Biology and Paleo Environment, Lamont-Doherty Earth Observatory, Palisades, NY 10964, USA.
| | - James M Russell
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02906, USA
| | - Avinash Subramanian
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02906, USA
| | - Rahab Kinyanjui
- Department of Earth Sciences, National Museums of Kenya, Nairobi 00100, Kenya
| | - Emily J Beverly
- Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77204, USA
| | - Kevin T Uno
- Division of Biology and Paleo Environment, Lamont-Doherty Earth Observatory, Palisades, NY 10964, USA
| | - Peter de Menocal
- Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA; Division of Biology and Paleo Environment, Lamont-Doherty Earth Observatory, Palisades, NY 10964, USA
| | - René Dommain
- Institute of Geosciences, University of Potsdam, 14476 Potsdam, Germany; Human Origins Program, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
| | - Richard Potts
- Human Origins Program, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA; Department of Earth Sciences, National Museums of Kenya, Nairobi 00100, Kenya
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Couvreur TL, Dauby G, Blach‐Overgaard A, Deblauwe V, Dessein S, Droissart V, Hardy OJ, Harris DJ, Janssens SB, Ley AC, Mackinder BA, Sonké B, Sosef MS, Stévart T, Svenning J, Wieringa JJ, Faye A, Missoup AD, Tolley KA, Nicolas V, Ntie S, Fluteau F, Robin C, Guillocheau F, Barboni D, Sepulchre P. Tectonics, climate and the diversification of the tropical African terrestrial flora and fauna. Biol Rev Camb Philos Soc 2021; 96:16-51. [PMID: 32924323 PMCID: PMC7821006 DOI: 10.1111/brv.12644] [Citation(s) in RCA: 64] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 08/07/2020] [Accepted: 08/13/2020] [Indexed: 12/30/2022]
Abstract
Tropical Africa is home to an astonishing biodiversity occurring in a variety of ecosystems. Past climatic change and geological events have impacted the evolution and diversification of this biodiversity. During the last two decades, around 90 dated molecular phylogenies of different clades across animals and plants have been published leading to an increased understanding of the diversification and speciation processes generating tropical African biodiversity. In parallel, extended geological and palaeoclimatic records together with detailed numerical simulations have refined our understanding of past geological and climatic changes in Africa. To date, these important advances have not been reviewed within a common framework. Here, we critically review and synthesize African climate, tectonics and terrestrial biodiversity evolution throughout the Cenozoic to the mid-Pleistocene, drawing on recent advances in Earth and life sciences. We first review six major geo-climatic periods defining tropical African biodiversity diversification by synthesizing 89 dated molecular phylogeny studies. Two major geo-climatic factors impacting the diversification of the sub-Saharan biota are highlighted. First, Africa underwent numerous climatic fluctuations at ancient and more recent timescales, with tectonic, greenhouse gas, and orbital forcing stimulating diversification. Second, increased aridification since the Late Eocene led to important extinction events, but also provided unique diversification opportunities shaping the current tropical African biodiversity landscape. We then review diversification studies of tropical terrestrial animal and plant clades and discuss three major models of speciation: (i) geographic speciation via vicariance (allopatry); (ii) ecological speciation impacted by climate and geological changes, and (iii) genomic speciation via genome duplication. Geographic speciation has been the most widely documented to date and is a common speciation model across tropical Africa. We conclude with four important challenges faced by tropical African biodiversity research: (i) to increase knowledge by gathering basic and fundamental biodiversity information; (ii) to improve modelling of African geophysical evolution throughout the Cenozoic via better constraints and downscaling approaches; (iii) to increase the precision of phylogenetic reconstruction and molecular dating of tropical African clades by using next generation sequencing approaches together with better fossil calibrations; (iv) finally, as done here, to integrate data better from Earth and life sciences by focusing on the interdisciplinary study of the evolution of tropical African biodiversity in a wider geodiversity context.
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Affiliation(s)
| | - Gilles Dauby
- AMAP Lab, IRD, CIRAD, CNRS, INRAUniversity of MontpellierMontpellierFrance
- Laboratoire d'évolution Biologique et Ecologie, Faculté des SciencesUniversité Libre de BruxellesCP160/12, Avenue F.D. Roosevelt 50Brussels1050Belgium
| | - Anne Blach‐Overgaard
- Section for Ecoinformatics & Biodiversity, Department of BiologyAarhus UniversityNy Munkegade 114Aarhus CDK‐8000Denmark
- Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of BiologyAarhus UniversityNy Munkegade 114Aarhus CDK‐8000Denmark
| | - Vincent Deblauwe
- Center for Tropical Research (CTR), Institute of the Environment and SustainabilityUniversity of California, Los Angeles (UCLA)Los AngelesCA90095U.S.A.
- International Institute of Tropical Agriculture (IITA)YaoundéCameroon
| | | | - Vincent Droissart
- AMAP Lab, IRD, CIRAD, CNRS, INRAUniversity of MontpellierMontpellierFrance
- Laboratoire de Botanique Systématique et d'Écologie, École Normale SupérieureUniversité de Yaoundé IPO Box 047YaoundéCameroon
- Herbarium et Bibliothèque de Botanique AfricaineUniversité Libre de BruxellesBoulevard du TriompheBrusselsB‐1050Belgium
- Africa & Madagascar DepartmentMissouri Botanical GardenSt. LouisMOU.S.A.
| | - Oliver J. Hardy
- Laboratoire d'évolution Biologique et Ecologie, Faculté des SciencesUniversité Libre de BruxellesCP160/12, Avenue F.D. Roosevelt 50Brussels1050Belgium
| | - David J. Harris
- Royal Botanic Garden Edinburgh20A Inverleith RowEdinburghU.K.
| | | | - Alexandra C. Ley
- Institut für Geobotanik und Botanischer GartenUniversity Halle‐WittenbergNeuwerk 21Halle06108Germany
| | | | - Bonaventure Sonké
- Laboratoire de Botanique Systématique et d'Écologie, École Normale SupérieureUniversité de Yaoundé IPO Box 047YaoundéCameroon
| | | | - Tariq Stévart
- Herbarium et Bibliothèque de Botanique AfricaineUniversité Libre de BruxellesBoulevard du TriompheBrusselsB‐1050Belgium
- Africa & Madagascar DepartmentMissouri Botanical GardenSt. LouisMOU.S.A.
| | - Jens‐Christian Svenning
- Section for Ecoinformatics & Biodiversity, Department of BiologyAarhus UniversityNy Munkegade 114Aarhus CDK‐8000Denmark
- Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of BiologyAarhus UniversityNy Munkegade 114Aarhus CDK‐8000Denmark
| | - Jan J. Wieringa
- Naturalis Biodiversity CenterDarwinweg 2Leiden2333 CRThe Netherlands
| | - Adama Faye
- Laboratoire National de Recherches sur les Productions Végétales (LNRPV)Institut Sénégalais de Recherches Agricoles (ISRA)Route des Hydrocarbures, Bel Air BP 1386‐ CP18524DakarSenegal
| | - Alain D. Missoup
- Zoology Unit, Laboratory of Biology and Physiology of Animal Organisms, Faculty of ScienceUniversity of DoualaPO Box 24157DoualaCameroon
| | - Krystal A. Tolley
- South African National Biodiversity InstituteKirstenbosch Research CentrePrivate Bag X7, ClaremontCape Town7735South Africa
- School of Animal, Plant and Environmental SciencesUniversity of the WitwatersrandPrivate Bag 3Wits2050South Africa
| | - Violaine Nicolas
- Institut de Systématique, Evolution, Biodiversité (ISYEB), Muséum national d'Histoire naturelle, CNRS, Sorbonne Université, EPHEUniversité des AntillesCP51, 57 rue CuvierParis75005France
| | - Stéphan Ntie
- Département de Biologie, Faculté des SciencesUniversité des Sciences et Techniques de MasukuFrancevilleBP 941Gabon
| | - Frédiéric Fluteau
- Institut de Physique du Globe de Paris, CNRSUniversité de ParisParisF‐75005France
| | - Cécile Robin
- CNRS, Géosciences Rennes, UMR6118University of RennesRennes35042France
| | | | - Doris Barboni
- CEREGE, Aix‐Marseille University, CNRS, IRD, Collège de France, INRA, Technopole Arbois MéditerranéeBP80Aix‐en‐Provence cedex413545France
| | - Pierre Sepulchre
- Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA‐CNRS‐UVSQUniversité Paris‐SaclayGif‐sur‐YvetteF‐91191France
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Skonieczny C, McGee D, Winckler G, Bory A, Bradtmiller LI, Kinsley CW, Polissar PJ, De Pol-Holz R, Rossignol L, Malaizé B. Monsoon-driven Saharan dust variability over the past 240,000 years. SCIENCE ADVANCES 2019; 5:eaav1887. [PMID: 30613782 PMCID: PMC6314818 DOI: 10.1126/sciadv.aav1887] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 11/21/2018] [Indexed: 06/09/2023]
Abstract
Reconstructions of past Saharan dust deposition in marine sediments provide foundational records of North African climate over time scales of 103 to 106 years. Previous dust records show primarily glacial-interglacial variability in the Pleistocene, in contrast to other monsoon records showing strong precessional variability. Here, we present the first Saharan dust record spanning multiple glacial cycles obtained using 230Th normalization, an improved method of calculating fluxes. Contrary to previous data, our record from the West African margin demonstrates high correlation with summer insolation and limited glacial-interglacial changes, indicating coherent variability in the African monsoon belt throughout the late Pleistocene. Our results demonstrate that low-latitude Saharan dust emissions do not vary synchronously with high- and mid-latitude dust emissions, and they call into question the use of existing Plio-Pleistocene dust records to investigate links between climate and hominid evolution.
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Affiliation(s)
- C. Skonieczny
- Laboratoire Géosciences Paris-Sud, UMR CNRS 8148, Université de Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - D. McGee
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - G. Winckler
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
- Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA
| | - A. Bory
- Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
- Université de Lille, CNRS, Université Littoral Cote d’Opale, UMR 8187, LOG, Laboratoire d’Océanologie et de Géosciences, Lille, France
| | - L. I. Bradtmiller
- Department of Environmental Studies, Macalester College, St. Paul, MN, USA
| | - C. W. Kinsley
- Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - P. J. Polissar
- Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA
| | - R. De Pol-Holz
- GAIA-Antártica, Universidad de Magallanes, Punta Arenas, Chile
| | - L. Rossignol
- Laboratoire Environnements et Paléoenvironnements Océaniques et Continentaux, UMR CNRS 5805, Université de Bordeaux, Pessac, France
| | - B. Malaizé
- Laboratoire Environnements et Paléoenvironnements Océaniques et Continentaux, UMR CNRS 5805, Université de Bordeaux, Pessac, France
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Foley RA, Martin L, Mirazón Lahr M, Stringer C. Major transitions in human evolution. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0229. [PMID: 27298461 DOI: 10.1098/rstb.2015.0229] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/20/2016] [Indexed: 11/12/2022] Open
Abstract
Evolutionary problems are often considered in terms of 'origins', and research in human evolution seen as a search for human origins. However, evolution, including human evolution, is a process of transitions from one state to another, and so questions are best put in terms of understanding the nature of those transitions. This paper discusses how the contributions to the themed issue 'Major transitions in human evolution' throw light on the pattern of change in hominin evolution. Four questions are addressed: (1) Is there a major divide between early (australopithecine) and later (Homo) evolution? (2) Does the pattern of change fit a model of short transformations, or gradual evolution? (3) Why is the role of Africa so prominent? (4) How are different aspects of adaptation-genes, phenotypes and behaviour-integrated across the transitions? The importance of developing technologies and approaches and the enduring role of fieldwork are emphasized.This article is part of the themed issue 'Major transitions in human evolution'.
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Affiliation(s)
- Robert A Foley
- Leverhulme Centre for Human Evolutionary Studies, University of Cambridge, Cambridge CB2 1QH, UK
| | - Lawrence Martin
- Turkana Basin Institute, Stony Brook University, Stony Brook, NY 11794-4364, USA
| | - Marta Mirazón Lahr
- Leverhulme Centre for Human Evolutionary Studies, University of Cambridge, Cambridge CB2 1QH, UK
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8
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Abstract
Aridification is often considered a major driver of long-term ecological change and hominin evolution in eastern Africa during the Plio-Pleistocene; however, this hypothesis remains inadequately tested owing to difficulties in reconstructing terrestrial paleoclimate. We present a revised aridity index for quantifying water deficit (WD) in terrestrial environments using tooth enamel δ18O values, and use this approach to address paleoaridity over the past 4.4 million years in eastern Africa. We find no long-term trend in WD, consistent with other terrestrial climate indicators in the Omo-Turkana Basin, and no relationship between paleoaridity and herbivore paleodiet structure among fossil collections meeting the criteria for WD estimation. Thus, we suggest that changes in the abundance of C4 grass and grazing herbivores in eastern Africa during the Pliocene and Pleistocene may have been decoupled from aridity. As in modern African ecosystems, other factors, such as rainfall seasonality or ecological interactions among plants and mammals, may be important for understanding the evolution of C4 grass- and grazer-dominated biomes.
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