Paleogeographic variations of pedogenic carbonate d 13C values from Koobi Fora,Kenya:implications for ?oral compositions
of Plio-Pleistocene hominin environments
Rhonda L.Quinn a ,b ,*,Christopher J.Lepre a ,James D.Wright b ,Craig S.Feibel a ,b
a Department of Anthropology,Rutgers University,131George Street,New Brunswick,NJ 08901,USA b
Department of Geological Sciences,Rutgers University,610Taylor Road,Piscataway,NJ 08854,USA
Received 4November 2005;accepted 22January 2007
Abstract
Plio-Pleistocene East African grassland expansion and faunal macroevolution,including that of our own lineage,are attributed to global climate change.To further understand environmental factors of early hominin evolution,we reconstruct the paleogeographic distribution of veg-etation (C 3-C 4pathways)by stable carbon isotope (d 13C)analysis of pedogenic carbonates from the Plio-Pleistocene Koobi Fora region,north-east Lake Turkana Basin,Kenya.We analyzed 202nodules (530measurements)from ten paleontological/archaeological collecting areas spanning environments over a 50-km 2area.We compared results across subregions in evolving ?uviolacustrine depositional environments in the Koobi Fora Formation from 2.0e 1.5Ma,a stratigraphic interval that temporally brackets grassland ascendancy in East Africa.Signi?cant differences in d 13C values between subregions are explained by paleogeographic controls on ?oral composition and distribution.Our results indicate grassland expansion between 2.0and 1.75Ma,coincident with major shifts in basin-wide sedimentation and hydrology.
Hypotheses may be correct in linking Plio-Pleistocene hominin evolution to environmental changes from global climate;however,based on our results,we interpret complexity from proximate forces that mitigated basin evolution.An w 2.5Ma tectonic event in southern Ethiopia and northern Kenya exerted strong effects on paleography in the Turkana Basin from 2.0e 1.5Ma,contributing to the shift from a closed,lacustrine basin to one dominated by open,?uvial conditions.We propose basin transformation decreased residence time for Omo River water and ex-panded subaerial ?oodplain landscapes,ultimately leading to reduced proportions of wooded ?oras and the establishment of habitats suitable for grassland communities.
ó2007Elsevier Ltd.All rights reserved.
Keywords:Paleogeography;Savannas;East Africa;Carbon isotopes
Introduction
Global climate is often elected as a catalyst for environmen-tal changes acting as selective pressures on Plio-Pleistocene African hominins (Stanley,1992;Vrba,1995,1999;deMeno-cal,2004).Habitat theory of Vrba (1992)and variability selec-tion hypothesis of Potts (1998)credit mammalian evolutionary pattern and process to climate change.Feibel (1999:276)
argues the need for a middle ground,tethering the ‘‘global-scale climatic phenomena’’to ‘‘environmental change,habitat shift,and biotic evolution’’,and offers the sedimentary basin as a scale for analysis.Environments within individual basins re-spond to climate with different sensitivities and thresholds in?uenced by basin size,topography,depositional and tectonic regime,and water availability (Carroll and Bohacs,1999;Withjack et al.,2002).
Stable carbon isotope (d 13C)records from pedogenic car-bonates are interpreted as re?ecting the spread of C 4grasses in East Africa beginning as early as the Miocene (Cerling,1992).From these data,environmental change and increased
*Corresponding author.
E-mail address:rlquinn@https://www.doczj.com/doc/317824840.html, (R.L.Quinn).
0047-2484/$-see front matter ó2007Elsevier Ltd.All rights reserved.
doi:10.1016/j.jhevol.2007.01.013
Journal of Human Evolution 53(2007)560e
573
aridity associated with global climate are temporally corre-lated with faunal macroevolution including the branching pat-tern of the hominin lineage and the origins of genus Homo(see review in deMenocal,2004).Unlike proxies of global climate from the marine realm,pedogenic carbonate isotopes offer di-rect and local environmental information from the habitats of hominins and other members of the mammalian community. Isotopic studies of pedogenic carbonates in the Turkana Basin have interpreted terrestrial East Africa as responsive to global climate over approximately the last four million years(Cerling et al.,1988;Wynn,2004).Here we employ stable isotopic values of paleosol carbonates from hominin-bearing sediment in the Koobi Fora region of the basin to examine paleoenvir-onmental change.We focus on the interval2.0e1.5Ma,which brackets a marked shift in aridity(Wynn,2004)and the ap-pearance of early African Homo erectus in the area(Anto′n and Swisher,2004;Wood and Strait,2004).We enlarge the current database to place our isotopic measures of?oral com-munity structure into a paleogeographic framework and inte-grate climatic and tectonic in?uences on a basin-wide scale. Study region
Geographic setting
The Turkana Basin of northern Kenya and southern Ethio-pia lies within the eastern branch(or Gregory Rift)of the East African Rift System between the Kenyan and Ethiopian domes (Ebinger et al.,2000).The basin presently contains one of the largest rift lakes,Lake Turkana,with an area of7,500km2 (Frostick,1997).Today,the lake is a saline-alkaline and closed-basin lake that receives over90%of its water from rainfall over the Ethiopian Highlands,via the Omo River (Fig.1),with minor inputs from the Turkwell and Kerio River systems(Yuretich,1979).The general climate within this rift bottom setting is arid to semi-arid and receives250e 500mm of rainfall annually(Nicholson,1996).Bushland grasslands dominate the landscape,with gallery forests clus-tered along perennial and ephemeral river channels(Lind and Morrison,1974).
The Koobi Fora region,situated within the northeast Tur-kana Basin of Kenya(Fig.1),is one of the richest fossil and archaeological localities in East Africa(Leakey and Leakey, 1978;Isaac and Isaac,1997).Plio-Pleistocene sediments ex-posed in the region are attributed to the Koobi Fora Formation (Brown and Feibel,1986),which preserves a record of homi-nin evolution and environmental change for the period w4.0e 1.0Ma(Feibel et al.,1989,1991;Brown and Feibel,1991). Lake Turkana constrains the western margin of the Koobi Fora Formation,while Miocene-Pliocene volcanics to the west de?ne the eastern border(Watkins,1986).The formation is exposed in geographic subregions of the Koobi Fora region, including Ileret,Il Dura,Karari Ridge,and Koobi Fora Ridge (Fig.2A),which are segregated into numbered paleontological and archaeological collecting areas(Fig.1).The extensive geographic exposure of the Koobi Fora Formation,and its well-documented stratigraphy and geochronology,affords reconstruction of a range of habitats across paleolandscapes at discrete temporal intervals.
Stratigraphy and paleogeography
Although outcrops of the Koobi Fora Formation are discon-tinuous,stratigraphic control has been determined by radiomet-rically dated and correlated tuffs,aerially extensive bioclastic lacustrine marker beds,and an established geomagnetic polar-ity stratigraphy(McDougall,1985;Brown and Feibel,1986, 1991;Hillhouse et al.,1986;Feibel et al.,1989;McDougall et al.,1992;Brown et al.,2006;McDougall and Brown, 2006;Fig.3).Here we focus on the upper Burgi,KBS,and lower Okote Members of the formation,approximately repre-senting the period between 2.0and 1.5Ma(McDougall, 1985;Brown and Feibel,1986,1991:*Age of Lorenyang Tuff is approximated by sedimentation rate(scaled
age). Fig.1.Location map of Lake Turkana and the Koobi Fora Formation(stippled area).Inset map shows shaded collecting areas used in this study(after Brown and Feibel,1991;Feibel et al.,1991;Feibel,1999).
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R.L.Quinn et al./Journal of Human Evolution53(2007)560e573
Fig.2.Paleogeographic reconstructions of the Koobi Fora Formation between 2.0and 1.5Ma (after Feibel,1988;Feibel et al.,1991;Rogers et al.,1994).A)Modern paleogeography,basemap area equals approximately 50km 2(after Isaac and Behrensmeyer,1997).B)Paleogeography at 1.7e 1.5Ma.C)Paleogeography at 1.8e 1.7Ma.D)Paleogeography at 1.9e 1.8Ma.E)Paleogeography at 2.0e 1.9Ma.
562R.L.Quinn et al./Journal of Human Evolution 53(2007)560e 573
Sedimentation of these members is inferred to be largely con-tinuous,except for an unconformity (w 500,000-year deposi-tional pause)in the upper portion of the Burgi Member (Fig.4)and the background hiatuses inherent to the sedimenta-tion of the ?uviolacustrine environments (Brown and Feibel,1986;Feibel et al.,1989,1991).
A large lake formed in the Turkana Basin at about 2.0Ma,as indicated by the widespread occurrence of lacustrine and asso-ciated facies just above the upper Burgi Member unconformity (Brown and Feibel,1991).This precursor of Lake Turkana,Lake Lorenyang (Fig.2E),occupied an area of approximately 9,000km 2,mainly fed by an ancestor of the modern Omo River (Feibel et al.,1991;Feibel,1997).
The deposition of the Lorenyang and KBS Tuffs in a deltaic facies (Feibel,1988)suggests that the ancestral Omo River delta began prograding into the Koobi Fora region by about 1.9Ma (Brown and Feibel,1991;Fig.2D).The river coursed through the region as indicated by ?uvial channel and ?ood-plain facies just above the stratigraphic level of the KBS Tuff (White et al.,1981).
Channel and ?oodplain deposits are more widespread within the upper part of the Olduvai Subchron,suggesting an increase in the prevalence of ancestral Omo River environments at Koobi Fora near 1.8e 1.7Ma (Feibel et al.,1989;Brown and Feibel,1991;McDougall et al.,1992).Additional channel systems em-anated from the highlands along the northeastern basin margin at this time (Feibel et al.,1991).The Omo River and basin margin channels emptied into a shallow lake margin/series of lake margins,over which there were frequent transgressions and regressions (Feibel et al.,1991;Feibel,1994;Fig.2C).After about 1.7Ma,lake-related depositional environments were virtually absent from the region,except for a few shal-low,aerially restricted,and transient examples (Brown and Feibel,1991;Fig.2B).For the majority of the period between 1.7and 1.4Ma,the main (axial)channels of the ancestral Omo were not readily active in the study area,rather the landscape was occupied by smaller distributaries that either derived from the main channel or from the northeastern margin of the basin (Feibel et al.,1991;Fig.2B).These distributaries were respon-sible for the deposition of a series of correlative marker tuffs,referred to as the Okote Tuff Complex,Koobi Fora Tuff Com-plex,and Ileret Tuff,which have an age near 1.6e 1.5Ma (Brown and Feibel,1985,1986;Brown et al.,2006;McDou-gall and Brown,2006).Large river channels,attributed to the ancestral Omo,reclaimed the Koobi Fora region near early Chari Member times,w 1.4Ma (Brown and Feibel,1991).East African and Turkana Basin paleoenvironments
Many studies attribute a marked increase in East African aridity and grassland expansion between 2.0and 1.5Ma to causes derived from global climate change (reviewed in deMe-nocal,2004).Increased terrigenous sediment inputs,ca.1.7Ma,from the northern low-latitude areas of continental Africa (deMenocal and Bloemendal,1995)have been linked with an intensi?cation of Northern Hemisphere Glaciation at w 1.8Ma (e.g.,Shackleton et al.,1990;Shackleton,1995
).
https://www.doczj.com/doc/317824840.html,posite stratigraphic sections of Koobi Fora Formation by subre-gions with radiometric ages of tuffs (after Brown and Feibel,1991;McDougall and Brown,2006).
563
R.L.Quinn et al./Journal of Human Evolution 53(2007)560e 573
Indications of a response to high-latitude glacial conditions are found in marine pollen records from off the coast of northwest Africa,which show wooded savanna to desert vegetation zones appearing around 2.6e 2.4Ma and dominating by 1.8Ma (Le-roy and Dupont,1994).East African palynological evidence suggests drier conditions in rift valley lowlands at 2.35Ma and an intensi?cation of aridity at around 1.8Ma (Bonne?lle,1995).East and South African mammalian species abundances show a shift to more arid-adapted fauna culminating at 1.8Ma (e.g.,Vrba,1995;Reed,1997).Pedogenic carbonate isotope re-cords amassed from several Plio-Pleistocene East African lo-calities also display aridi?cation with increased proportions of C 4grasses and heightened evaporation of soil water or change in isotopic composition of rainfall (Cerling,1992;Levin et al.,2004;Wynn,2004).
Other researchers,however,have found ambiguous or con-trasting records of East African paleoenvironments.Kingston and others (1994)found no signi?cant change in vegetation from the Baringo Basin,but a persistent mosaic environment over the last 15Ma.Plio-Pleistocene vegetation at Olduvai Gorge had a signi?cant amount of wooded vegetation (Sikes,1994).Trauth et al.(2005,2007)have suggested the presence of a humid period within the general pattern of East African aridi?cation indicated by the formation of large lakes circa 1.9e 1.7Ma.Suids found in South and East African hominin localities maintain postcranial morphologies for closed and in-termediate habitats (Bishop,1999).
Within the Turkana Basin,contrasting and complex proxy records also confound environmental interpretations.Mamma-lian species abundances show a gradual shift to more arid-adapted fauna from 2.5to 1.8Ma rather than a ‘‘turnover pulse’’coinciding with glacial intensi?cation (Behrensmeyer et al.,1997).Additional studies on the same dataset proposed a series of pulses occurring at periods of 100,000years (Bobe and Behrensmeyer,2004).Palynological evidence indicates
that grass species dominated from lake and delta environments at 2.0Ma (Bonne?lle and Vincens,1985);however,cooler and more humid conditions have been interpreted in areas of the basin by the presence of highland and riverine pollen species (Bonne?lle,1976).Cerling and others (1988)and Wynn (2000)demonstrated tropical grass expansion in the Turkana Basin over the last 4.3Ma,with marked aridity events during the intervals between 3.58e 3.35, 2.52e 2.00,and 1.81e 1.58Ma.However,Wynn’s (2004:his ?gure 2B)compilation illustrated a mean value trending toward wooded vegetation between 1.8e 1.5Ma.Wynn (2004)also reported a general ari-di?cation trend with increasingly shallower calcic horizon depths in Turkana Basin paleosols,although he found an ex-cursion to a humid period between 1.9and 1.8Ma with depth to calcic horizon estimates.Materials and methods
Stable carbon isotopes (d 13C)of pedogenic carbonates The C 3(Calvin-Benson)and C 4(Hatch-Slack)photosyn-thetic pathways have distinct differences in the fractionation of carbon isotopes (see Ehleringer,1989).Woodland vegeta-tion (trees,shrubs,temperate grasses)utilizing the C 3pathway discriminate against the heavier and kinetically slower isotope of carbon,13C;whereas tropical grasses using the C 4pathway also discriminate but allow the inclusion of more 13C into tis-sues than do C 3?ora.Since most low-latitude grasses use the C 4pathway,East African vegetation shows a clear separation in d 13C values (C 3:à31.4to à24.6&,C 4:à14.1to à11.5&;Cerling et al.,2003).
Following soil gas diffusion models of Cerling (1984)and Cerling and Quade (1993)and the conditions of respiration rates developed by Quade et al.(1989),pedogenic carbonates at depths greater than 30cm in soils with relatively
high
Fig.4.Sedimentation rates and depositional hiatuses for the Koobi Fora Formation throughout its depositional history (after Feibel,1988).
564R.L.Quinn et al./Journal of Human Evolution 53(2007)560e 573
respiration rates incorporate CO2of decaying organic matter derived from surface vegetation during soil development. d13C values of pedogenic carbonates from the savanna biome are intermediate between the C3-C4end members and re?ect the percentage of grasses versus woody vegetation present on the land surface with an isotopic fractionation between13.5e 16.6&(Cerling and Quade,1993).Pedogenic carbonates form under a negative water budget in regions with rainfall be-low100cm/yr during periods averaging hundreds to thousands of years(Jenny,1941,1980;Birkeland,1984;Srivastava, 2001).Fossil soils preserved in the Plio-Pleistocene Koobi Fora Formation are dominated by paleovertisols,formed under a dry season of four or more months and250e1,000mm of annual moisture(Feibel,1988;Wynn,2000,2004).
Soil carbonate sampling strategy and analysis
We examined pedogenic carbonate isotope(d13C)values from paleosols to reconstruct geographic distribution of vege-tation(C3-C4pathways)through time to assess the nature, timing,and controls on paleoenvironmental change in homi-nin-associated habitats of Koobi Fora.We compared lake-margin,river?oodplain,and distributary channel?oodplain depositional landscapes for the period of w2.0e1.5Ma that temporally brackets grassland ascendancy in East Africa as documented in Wynn’s(2004)third C4expansion event.We enhanced the previous isotopic studies of pedogenic carbon-ates from the Turkana Basin(Cerling et al.,1988;Wynn, 2004)for the2.0e1.5Ma time interval by:1)increasing the sample size(nodules,n?202;analyses,n?530),and2)con-ducting widespread sampling of synchronous lateral horizons in the Koobi Fora Formation.This lateral sampling approach has been suggested for attaining ecotonal variability and hab-itat gradient(e.g.,Kingston et al.,1994;Levin et al.,2004; Wynn,2004).With attention to paleohydrology(after Levin et al.,2004),we partitioned the northeast Turkana Basin as subregions by proximity to precursors of Lake Turkana and to the ancestral Omo River system,which was the main con-trol of basin-wide hydrology and deposition during the Plio-Pleistocene(e.g.,Feibel et al.,1991).
Our study interval begins with the upper Burgi Member (2.0to1.9Ma),spans the entire KBS Member(1.9to1.6e 1.5Ma),and ends with the lower portion of the Okote Member [1.6e1.5Ma(e.g.,Brown and Feibel,1986,1991;McDougall and Brown,2006)].We sampled exposures from collecting area1a in the Ileret subregion,area41in the Il Dura subre-gion,areas101,102,103,and104along the Koobi Fora Ridge,and areas105,130,131,and133on the Karari Ridge (Fig.1).Our study covers approximately50km2in total area of exposure and examines evolving paleolandscapes along lake-margin areas and?oodplain areas.The Koobi Fora Ridge and Karari Ridge span three and four of the environments through time,respectively,whereas the Il Dura and Ileret sub-regions only record one depositional regime(Fig.2B e E).
Age control of pedogenic carbonate samples was deter-mined with the established chronostratigraphic framework and scaled with sedimentation rates for each subregion.For example,with the KBS Tuff dated to1.87Ma(McDougall and Brown,2006)and an average sedimentation rate of the Karari Escarpment determined as6.2cm/kyr(Feibel,1988), we calculated a fossil soil located?ve meters above the KBS Tuff in collecting Area105to be approximately 1.79Ma.All ages are expected to have an error of0.03e 0.05Ma(e.g.,Feibel et al.,1989).
In addition to the sedimentological indicators of paleogeog-raphy,we used paleopedology to interpret environmental con-text of the isotopic results.At the outcrop,we identi?ed pedogenic carbonate and paleosols by criteria set forth in Re-tallack(2001)and re?ned for the Turkana Basin by Wynn (2000,2001,2004).We sampled pedogenic carbonates in the preserved calcic horizon of the paleosol at a minimum of30cm below the contact with the overlying stratum,as sug-gested by Quade and others(1989),and excavated back from the vertically exposed surface by approximately50cm(e.g., Sikes,1994).Calcite nodules were extracted from within indi-vidual peds.Since most Turkana fossil soils are paleovertisols, they show vertic features and slickensided surfaces;we chose calcite nodules that exhibited slickensides and/or were adjacent to slickenslided surfaces.Although abundant in the formation deposits,we did not include calcareous rhizoliths in this study due to isotopic alteration by shallow cementation(Driese and Mora,1993)and groundwater(Liutkus et al.,2005).
In the laboratory,we sectioned pedogenic nodules and sam-pled micritic portions with a0.5mm carbide drill bit(Foredom Series),avoiding surface and sparry calcite.We subsampled nodules2e6times depending on size in order to test for internal nodular variability and averaged the subsample values.Approx-imately5%of the samples were analyzed by cathodolumines-cence(CL)to test for groundwater contribution(Marshall, 1988;Wynn,2004).All isotopic analyses were conducted at the Stable Isotope Laboratory at Rutgers University on a Micro-mass Optima Mass Spectrometer with an attached Multi-Prep device.Samples were reacted in100%phosphoric acid at 90 C for13minutes.d13C values are reported versus the Pee Dee Belemnite reference standard(V-PDB)through analysis of the laboratory standard(NBS-19)with values of1.95&for d13C(Coplen et al.,1983).
We used Wynn’s(2000,2001)savanna environment cate-gories to interpret the d13C values as they re?ect?oral com-munity structure and composition.We acknowledge the ?uidity of ecotonal boundaries,but attempt to explain?oral community change with statistically signi?cant shifts in d13C values.As widespread sampling of fossil soils at one interval potentially yields a wide range of isotopic ratios spanning the values of C3-C4communities,we approached the question of signi?cant change in vegetation across space and through time in the following ways.In order to gauge change in veg-etation across space,we compared results by subregion,due to position within the basin(e.g.,proximal to the basin margin, proximal to the lake shore).For change in vegetation through time,we delineated brackets of time that witnessed major changes in paleogeography.Paleogeographic interpretations are based on sedimentary evidence and provide the context for our isotopic results.We present our results in100-kyr
565
R.L.Quinn et al./Journal of Human Evolution53(2007)560e573
intervals that con?ne major changes of paleogeography and deposition: 2.0e1.9Ma, 1.9e1.8Ma, 1.8e1.7Ma, 1.7e 1.6Ma,and1.6e1.5Ma.The last two intervals record the same depositional environment.We also examined the results by subregion and by subregion within100-kyr intervals.In all approaches,we treated our groups as populations and com-pared means and variances between groups with one-way AN-OV A,Tukey’s all pairs comparison,and Kruskal-Wallis rank sum tests.We also interpolated change through time amongst all datapoints with a10%weighted smooth curve?t after Sti-neman(1980).All summary statistics and statistical analyses were conducted with KaleidagraphòSoftware.
Results and interpretation
d13C values of pedogenic carbonates
d13C values of all pedogenic carbonates from Koobi Fora yielded a mean ofà5.5&and standard deviation of1.6(Table 1).Summary statistics are shown by formation and subregions (Table1)and by100-kyr intervals(Table2).Estimated with a10%weighted smooth curve?t,the formation shows a3& depletion in13C from2.0to1.75Ma.After1.75Ma,the curve ?uctuates within1&(Fig.5).Results from100-kyr intervals representing different depositional environments show that all are not likely drawn from one population(p<0.001). One-way ANOV A and Tukey’s all pairs comparison results are shown in Tables3and5.Four of ten paired comparisons show signi?cant differences between groups(p<0.001);the ?rst two100-kyr intervals(2.0e1.9Ma,1.9e1.8Ma)vary sig-ni?cantly from the next two100-kyr intervals(1.8e1.7Ma, 1.7e1.6Ma)(Table2;Fig.6).Kruskal-Wallis rank sum test corroborates the results of the one-way ANOV A(Table3).
Results by subregion for all time intervals also show mean-ingful differences between groups.One-way ANOV A and Tu-key’s all pairs comparison results are shown in Tables4and6. Kruskal-Wallis rank sum test yielded similar results(Table4). The data from the Karari Ridge and Il Dura are signi?cantly different from those of the Koobi Fora Ridge and Ileret (p<0.001;Fig.7).Furthermore,comparing the subregions within individual100-kyr intervals yields signi?cant differ-ences between groups(Fig.8).In the1.9e1.8Ma interval, data from the Karari Ridge,Il Dura,and Koobi Fora Ridge do not vary signi?cantly from one another.Results from the one-way ANOV A and Kruskal-Wallis rank sum test indicate that the samples are likely from the same distribution.However, results from the following three100-kyr intervals show that the subregions re?ect different populations(Fig.8);results from the one-way ANOV A and Kruskal-Wallis rank sum test corrob-orate the smooth curve?ts(p<0.001).In each of the 1.8e1.7Ma, 1.7e1.6Ma,and 1.6e1.5Ma intervals,data from the Karari subregion signi?cantly vary from those of the Koobi Fora Ridge and Ileret subregions(p<0.001).
Table1
Summary statistics by subregions
All subregions Koobi
Fora Ridge
Karari
Ridge
Ileret Il Dura
Sample size2027185397 Mean d13C valueà5.47à4.73à6.27à4.76à7.05 Median d13C valueà5.46à4.69à6.35à4.60à6.31 Minimum d13C valueà10.43à10.43à9.07à6.74à9.53 Maximum d13C value0.430.43à3.30à3.38à5.79 Standard deviation 1.63 1.85 1.190.87 1.59 Standard error0.110.220.130.140.60 Variance 2.65 3.40 1.420.77 2.52 Skewnessà0.04à0.470.06à0.52à0.89 Kurtosis 1.31 2.31à0.18à0.63à1.08Table2
Summary statistics by100-kyr intervals
2.0e1.9
Ma
1.9e1.8
Ma
1.8e1.7
Ma
1.7e1.6
Ma
1.6e1.5
Ma Sample size1154436232 Mean d13C valueà7.10à6.22à4.98à4.85à5.48 Median d13C valueà7.16à5.94à4.90à4.66à5.51 Minimum d13C valueà8.54à10.43à9.37à7.22à9.07 Maximum d13C valueà5.37à3.760.43à0.44à3.67 Standard deviation0.96 1.49 1.83 1.42 1.24 Standard error0.290.200.280.180.22 Variance0.92 2.21 3.36 2.02 1.53 Skewness0.16à1.010.100.52à0.81 Kurtosisà0.68 1.010.870.85
0.65
Fig.5.d13C(&)vs.age(Ma).Pedogenic carbonate d13C values from paleo-sols in the Koobi Fora Formation between2.0and1.5Ma.Black line repre-sents10%weighted smooth curve?t of all data points(B).Savanna categories are taken from Wynn(2000,2001).
566R.L.Quinn et al./Journal of Human Evolution53(2007)560e573
Interpretation of?oral compositions
The Koobi Fora Formation preserves a range of habitats from forest(minimum d13C:à10.4&)to savanna grassland (maximum d13C:0.4&)with the majority of environments falling in the mosaic compositions including savanna wood-land,thicket and scrub,and low-tree shrub savanna(mean d13C:à5.5&;interpreted after Wynn,2000,2001).Based on Cerling’s(1984)model of C4contribution to soil CO2,trop-ical grasses comprised46%of the average landscape and ranged from11e89%.Floral compositions by subregion are presented below(Table1;Figs.7and8).
Il Dura.Sampled paleosols are moderately to well-developed clay vertisols,based on thickness,ped structure,and large dish-shaped slickensides(e.g.,Aberegaiya variant after Wynn, 2000),with a soil moisture estimate of>1000mm/yr by calcic horizon at depth of approximately600e800cm(Wynn,2000, 2004).We observe low d13C values prior to1.8Ma,with grasses comprising35%(range:18e44%)of the?ora.We interpret woodland savanna and/or thicket and scrub environments in this subregion.
Ileret.The sampled Ileret soils are thin(40e60cm),imma-ture vertisols similar to Dite paleosols(Wynn,2000)based on their crumb ped structures,shallow calcic horizons,and their stratigraphic positions between channelized tuffs.Samples are from one depositional environment and?uctuate in d13C values betweenà6andà4&(Fig.8),constituting approxi-mately40e60%of grassy vegetation.We interpret the savanna category based on isotopic results primarily as low-tree shrub, with few woodland,and thicket and scrub environments.
Koobi Fora Ridge.Paleosols from the Koobi Fora Ridge vary markedly in morphology but generally show a high clas-tic content likely due to proximity to a?uctuating lake margin (Feibel,1988).One soil in particular,the Lorenyang pedotype (after Wynn,2004),is present at and after1.8Ma,and shows distinct sand-?lled surface cracks and a thick calcic horizon. This fossil soil has been interpreted to support seasonally sparse savanna grassland with little time for development due to quick burial(Wynn,2004).d13C results from this sub-region corroborate the previous interpretations of expansion of C4grasses after1.8Ma(Cerling et al.,1988;Wynn,2004). The weighted smooth curve of d13C values at1.9e1.8Ma in-creases fromà6toà4&(40e60%grasses),placing the area within the low-tree shrub category.After1.8Ma,the curve shifts to more open savanna grassland environments and then returns to the low-tree shrub category at1.65Ma(Fig.8).
Karari Ridge.The Karari paleosols show morphological di-versity.Below the KBS Tuff,the Karari shares the Aberegaiya paleosol with the Il Dura subregion.Directly underlying the Okote Tuff Complex(w1.6e1.5Ma),the Kimere pedotype
Table3
Results of one-way ANOV A and Kruskal-Wallis rank sum test of100-ky inter-val groups
One-way ANOV A DF SS MS F P Total201531.91 2.6510.51<0.0001 A493.5523.39
Error197438.35 2.23
Kruskal-Wallis
rank sum test
K-W statistic P
37.02<0.0001
Table4
Results of one-way ANOV A and Kruskal-Wallis rank sum test of subregion groups
One-way ANOV A DF SS MS F P Total201532.00 2.6521.47<0.0001 A3130.5843.53
Error198401.42 2.03
Kruskal-Wallis
rank sum test
K-W statistic P
63.20<0.0001Table5
Results of Tukey’s all pairs comparison by100-kyr interval groups Comparison Mean
difference
j q j P95%CL
(1.7-1.6)vs.(2.0-1.9) 2.25 6.52<0.00010.91e3.59 (1.7-1.6)vs.(1.9-1.8) 1.37 6.97<0.00010.60e2.13 (1.7-1.6)vs.(1.6-1.5)0.63 2.740.2998à0.26e1.52 (1.7-1.6)vs.(1.8-1.7)0.130.630.9916à0.68e0.95 (1.8-1.7)vs.(2.0-1.9) 2.12 5.940.00040.73e3.50 (1.8-1.7)vs.(1.9-1.8) 1.24 5.740.00070.40e2.08 (1.8-1.7)vs.(1.6-1.5)0.50 2.020.6105à0.46e1.46 (1.6-1.5)vs.(2.0-1.9) 1.62 4.390.01830.18e3.06 (1.6-1.5)vs.(1.9-1.8)0.74 3.140.1762à0.18e1.66 (1.9-1.8)vs.(2.0-1.9)0.88 2.520.3856à0.48e
2.24
Fig.6.Nonparametric box and whisker plots of d13C values(&)by100-kyr interval groups.
567
R.L.Quinn et al./Journal of Human Evolution53(2007)560e573
shows the presence of thick(w0.5m)columnar and slicken-sided carbonate horizon,suggesting a stable land surface and pedogenesis for a substantial period of time(e.g.,Wynn and Feibel,1995).Within the Okote Tuff Complex,soils are poorly developed and characterized as Dite paleosols similar to those found in the Ileret subregion.d13C values from mor-phologically different pedotypes preserved on the Karari Ridge do not show the grassland expansion trend.Before 1.9Ma,the smooth curve?t of d13C values?uctuates between à8andà6&(30e40%grasses),placing the subregion within the savanna woodland and thicket and scrub categories (Fig.8).We observe a1&increase after1.8Ma showing an excursion to the low-tree shrub category.By1.75Ma environ-ments have returned to the woodland and thicket savannas. Controls on d13C values and?oral compositions
Paleogeographical,sedimentological,and paleohydrological changes related to the precursors of Lake Turkana and the Omo River in?uenced?oral compositions and distributions through time.We suggest that differences in the isotopic ratios of pale-osol carbonates were controlled by the context of paleosols in relation to the inherent array of moisture and depositional conditions found in?uviolacustrine systems.We discuss four paleogeographic factors:water availability,sediment accumu-lation rates,ratios of subaqueous:subaerial land,and open and closed basin conditions.We also view tectonics(subsidence rates)as an important force on paleogeographic change that can lead to differential distributions of the isotopic data.As compared with paleoclimate,these tectonic-subsidence controls on paleogeographic change may have exerted an equal or greater in?uence on the observed?oral patterns. Paleogeographic controls on subregional d13C values We assume simple forcing relationships between paleogeo-graphic changes and?oral distribution.Wooded vegetation typi?es gallery forests clustered along channel banks of the modern Omo River.Tropical grasses are found in the lateral ?oodplain environments.Mixed communities are generally between the two areas in overbank environments with small channels dispersed within a?ood basin(Carr,1976).Results of C3-C4patterns by subregion illustrate these predictions.
Our results of the Il Dura subregion agree with the paleo-geographic location near the axial meandering proto-Omo River,where a higher proportion of C3vegetation is expected.Ileret paleosols are poorly developed and interpreted as indic-ative of?oodplain areas laden with small distributary channels of the ancestral Omo River,supporting low-tree shrubs and grasses.Our section from the Koobi Fora Ridge begins just af-ter1.9Ma,when a deltaic system begins to form along north-ern margins of Lake Lorenyang.Oscillations of lake-level after1.9Ma,coupled with high rates of clastic input from del-taic sedimentation,may have reduced suitable lake-margin habitats for woodland?oral communities,thus increasing the proportion of grasses.As compared with other subregions, the unique proximity to basin margin channel systems and paleogeographic history of the Karari Ridge may indicate a dif-ferent water availability regime and explain the exceptionally low d13C values.Marginal systems likely provided a consistent supply of water to C3?oral communities,buffering against variations spurred by paleographic shifts from lacustrine-related environments at w1.9e1.8Ma to?uvial channel and ?oodplains after1.8Ma.
Observed paleogeographic patterns in?uenced preservation of the soil carbonate and the manner in which vegetation is re-corded in isotopic values.Pedogenic carbonate formation is in-hibited near channel and lake-margin areas with high water tables and sedimentation rates(van Breemen and Buurman, 2002).As a result,our ability to reconstruct vegetation is limited to the drier subaerial portions of the landscape with carbonate precipitation.Sampling strategies for isotopic records from pa-leosol carbonates may be biased to strata of?oodplain environ-ments d the preferred habitats for tropical https://www.doczj.com/doc/317824840.html,ndscapes with a high proportion of?oodplains to channels may skew pa-leosol isotopic records toward a C4signal.Consequently,
Table6
Results of Tukey’s all pairs comparison by subregion groups
Comparison Mean Difference j q j P95%CL Koobi Fora vs.Il Dura 2.32 5.830.00030.86e3.79 Koobi Fora vs.Karari 1.549.52<0.00010.95e2.13 Koobi Fora vs.Ileret0.030.160.9994à0.70e0.77 Ileret vs.Il Dura 2.29 5.540.00070.78e3.81 Ileret vs.Karari 1.517.75<0.00010.80e2.22 Karari vs.Il Dura0.78 1.980.5027à0.67e
2.23
Fig.7.Nonparametric box and whisker plots of d13C values(&)by subregion
groups.
568R.L.Quinn et al./Journal of Human Evolution53(2007)560e573
carbonate isotopic values will not capture the pure C 3values in the savanna environment,but rather combine values from ?uc-tuating ?oral compositions as the meander belt avulses (Levin et al.,2004).For comparison,lacustrine systems have a compar-atively high proportion of subaqueous to subaerial landscapes,suggesting a low amount of suitable substrate for paleosol and pedogenic carbonate formation.These systems often have rela-tively faster sedimentation rates,which are not conducive for the prolonged development of soils (Jenny,1980;Retallack,2001,van Breemen and Buurman,2002).At 1.8Ma,river avul-sion away from the eastern basin (e.g.,Brown and Feibel,1991;Feibel et al.,1991)may have dampened C 3contributions to soil carbonate isotopic values.Subsequent emplacement of smaller ?uvial-distributary systems and expanded ?oodplain environ-ments (Fig.2)may have further reduced the signal of wooded vegetation.
Basin scale paleogeographic and tectonic factors
Basin scale factors of paleogeographic change also in?u-enced the character of paleosol and carbonate formation and
associated ?oral compositions.Tectonism was a strong driver of paleogeographic changes in the Koobi Fora region during the Plio-Pleistocene (Brown and Feibel,1991;Feibel et al.,1991).We propose an integrative explanation of paleogeo-graphic evolution that incorporates climate and tectonics after Carroll and Bohacs (1999)and Withjack and colleagues (2002).These authors suggest that diachronic changes in the ae-rial distributions,facies,and environments of lake basins result from the combined effects of tectonic subsidence and climate and their control on the rate of potential accommodation space (mostly tectonic subsidence)and the delivery of water and sed-iment to a basin (mostly climate).V olcano-tectonic events at w 2.5Ma changed subsidence and basin accommodation rates and contributed to the transformation of the Turkana Basin from a hydrologically closed lacustrine-dominated basin to an open ?uvial one over 2.0e 1.5Ma.We suggest that moisture and ?oral patterns are explained by resultant shifts in paleoge-ography,proportions of subaqueous landscapes relative to sub-aerial landscapes,and hydrologically open or closed basin conditions.Plio-Pleistocene grassland expansion at Koobi Fora is linked with expanded subaerial ?oodplains and expedi-ent basin water loss from the through-?owing ancestral Omo River,ultimately generated by tectonic-subsidence factors.According to the models of Carroll and Bohacs (1999)and Withjack and others (2002),a basin d which is under?lled with water and sediment (subsidence-accommodation >sediment-water input)d contains a closed lake system with in-puts from rivers,runoff,and precipitation but outputs only by means of evaporation.A balance-?lled basin (subsidence-accommodation ?sediment-water input)commonly contains an open lake system with relatively equal amounts of sediment and water input and output via rivers.An over?lled basin (subsidence-accommodation The presence of major unconformities in the Koobi Fora Formation (Fig.4)is associated with volcano-tectonic down-warping of the Turkana Basin and associated uplift of the Ethiopian Plateau in southern Ethiopia (Brown and Feibel,1991;Feibel et al.,1991).Our stratigraphic study interval begins just above the level of the upper Burgi un-conformity (w 2.5e 2.0Ma).This hiatus was generated by tectonic disruption in the basin evident by the Stephanie Uplift to the northeast and gentle tilting of the strata in the Koobi Fora region associated with an interval of synde-position (Feibel,1997).These structural movements induced by volcano-tectonics increased subsidence rates and accom-modation space in the Turkana Basin,leading to under?lled conditions.Our interpretation of the Koobi Fora region as an under?lled basin with a large degree of potential accom-modation space at w 2.5e 2.0Ma is supported by the plot of sedimentation rates for the entire Koobi Fora Formation (Fig.4),which suggests an exponential and positive in-crease in sediment accumulation beginning just after 1.9Ma and ending around 1.7Ma.Structural movements at about 2.5Ma resulted in increased subsidence rates and Fig.8.d 13C (&)vs.age (Ma).Pedogenic carbonate d 13C values of the Koobi Fora Formation between 2.0and 1.5Ma.Data points are separated by subre-gion:Il Dura (?),Karari Ridge (B ),Koobi Fora Ridge (>),Ileret (,).Black lines represent 10%weighted smooth curve ?t of points by subregion:Karari Ridge (solid line),Koobi Fora Ridge (broken line),Ileret (broken line with dots).Savanna categories are taken from Wynn (2000,2001). 569 R.L.Quinn et al./Journal of Human Evolution 53(2007)560e 573 ample space to accommodate a large in?ux of sediment into the basin between1.9e1.7Ma. Prior to about1.9Ma,the Turkana Basin had a?uvial out-let to the southeast but was occupied by a relatively deep and broad lake,Lake Lorenyang(Feibel,1994).The sedimentation rate curve(Fig.4)may indicate that there were relatively few sediments accumulating under a low proportion of sediment supply relative to accommodation rate;sedimentation was out-paced by the rate of subsidence generation.Evidence from pa-leogeography and sedimentation rates suggests that the basin was balanced-?lled or under?lled with sediment and over?lled with water(cf.,Carroll and Bohacs,1999;Withjack et al., 2002). The period between1.9and1.7Ma was a highly variable time in the basin with respect to depositional environments; lake waters became shallower,lake level frequently oscil-lated,and deltaic and?uvial environments were active during this interval(Fig.2).Beginning at1.9Ma and continuing to 1.7Ma,the sedimentation rate curve shows a shift to a near vertical trend that crosses to above the extrapolated mean sedimentation rate line(Fig.4).These patterns may indicate an‘‘instantaneous’’rate of sediment accumulation under conditions of a more equal or lower proportion of accommo-dation rates relative to sediment supply rates as compared to earlier times;sedimentation kept pace with or exceeded subsidence.The sedimentation rate curve and paleogeogra-phy support the interpretation that after1.7Ma the basin was progressing toward an in?lled status,over?lled after the models of Carroll and Bohacs(1999)and Withjack and others(2002). After1.7Ma,the sedimentation rate curve takes a sharp turn back towards the mean sedimentation rate line(decrease in the rate of sediment accumulation),which may suggest a lower proportion of accommodation relative to sediment supply rates as compared with the1.9e1.7Ma period;sedi-mentation outpaced subsidence.Brown and Feibel(1991)sug-gest that during1.7e1.4Ma the Turkana Basin had very few landscapes with lacustrine-related sedimentary environments, but there was a preponderance of?uvial channel and?ood-plain environments.The protracted transformation of the basin from a lacustrine-dominated setting to one with a through-?owing river suggests in?lling under a regime of progressively less tectonic subsidence(Carroll and Bohacs,1999;Withjack et al.,2002). Our examined stratigraphic interval brackets at least four successive times of differential sedimentation in the Plio-Pleistocene Turkana Basin,including periods of lacustrine, deltaic,shallow/?uctuating lacustrine,and?uvial channel and?oodplain deposition(Fig.2B e E).Previous research demonstrates that these periods are tracking the transformation of the basin from a hydrologically closed lake basin to one that is open with a through-?owing ancestral Omo River(Brown and Feibel,1991).Shifts in isotopic ratios and inferred?oral patterns are coeval with these periods(Figs.5and6).We in-terpret these data as indicating relatively wet conditions during lacustrine and deltaic intervals and dry conditions during shal-low/?uctuating lacustrine and?uvial intervals.We suggest moisture and?oral patterns are controlled by paleogeography, proportion of subaqueous relative to subaerial landscapes,and hydrologically open or closed basin conditions.In half-graben basins with lakes,there are high proportions of subaqueous landscapes relative to subaerial settings(cf.,Gawthorpe et al.,1994;Leeder et al.,1998;Gawthorpe and Leeder, 2000).Our?ndings of more closed savanna environments are associated with the lake basin pooling water and a lack of suitable subaerial substrate for well-developed pedogenic carbonates and grassland communities on which to form.In comparison,we associate through-?owing?uvial intervals with lower proportions of subaqueous to subaerial landscapes and hydrologically open conditions(Gawthorpe et al.,1994; Leeder et al.,1998;Gawthorpe and Leeder,2000).Indications of grassland expansion during these intervals may stem from pronounced water loss in the basin under an open hydrology. The?uvial intervals are coeval with isotopic evidence of grassland expansion and,by inference,increased aridity.We interpret this?nding as a result of a very low proportion of subaqueous relative to subaerial landscapes coupled with ex-pedient basin water loss from the through-?owing ancestral Omo River.The rise of the subaerial?uvial landscapes re-sulted in expansion of preferred?oodplain habitats for C4 vegetation. Climatic factors Overall,our results show a shift from C3vegetation and de-creased evaporation to higher C4proportions and evaporation increase during2.0e1.5Ma,which we can ultimately link to tectonic-subsidence,accommodation space,basin in?lling, and their control on paleohydrology.However,the establish-ment of grasslands recorded in the entire basin and East Africa after1.8Ma,initially proposed by Cerling(1992),suggests an overprint of a large-scale in?uence often attributed to global climate change.Changes in the isotopic character of water and vegetation in the Koobi Fora region during our study in-terval has been shown as a response to global climate change due to glacial activity in the Northern Hemisphere(see deMe-nocal,2004for a recent review),and as a result,may explain our observed shift in d13C values from2.0to1.75Ma.Based on the climate forcing model for the Turkana Basin proposed by Lepre et al.(2007),we would expect to observe cycles in water availability and,therefore,?uctuations in?oral commu-nities coinciding with orbital periodicities.We do not observe periodicities in our isotopic results.This is in part due to the preservation of soils though time(i.e.,there are large gaps in the stratigraphic record hindering continuous isotopic records). If climate is producing recurring sedimentary packages(e.g., deep lake,shallow lake,beach,paleosol),soil carbonates are recording only one segment of the orbital cycle.Moreover, soil carbonate isotopes are sensitive to local vegetation change, which potentially masks?oral changes on orbital timescales. Additional work with complementary isotopic proxy records of environmental change(e.g.,lacustrine invertebrates)may increase our understanding of climate’s role on the Turkana Basin. 570R.L.Quinn et al./Journal of Human Evolution53(2007)560e573 Implications for hominin environments at Koobi Fora Our d13C values indicate grassland expansion from2.0to 1.75Ma,trending from more closed savanna woodlands to more open low-tree shrub savannas.Environments?uctuated within the low-tree shrub savanna category from 1.75to 1.5Ma.We propose that habitat fragmentation increased; that is,wooded environments are maintained,and the mosaic and grassland pieces are expanded.Behrensmeyer and others (1997)interpreted faunal turnover as a slow process in the Tur-kana Basin between2.5and1.8Ma rather than a short-term pulse coinciding with the onset of Northern Hemisphere Gla-ciation between2.8and2.5Ma.Our change in average?oral composition between2.0and1.75Ma coincides with one of the highest faunal turnover pulses in the Turkana Basin(Beh-rensmeyer et al.,1997;Bobe and Behrensmeyer,2004).Based on our interpretation of paleogeographic controls on?oral dis-tribution,the timing of faunal turnover is coeval with the trans-formation of the basin from a closed lacustrine-dominated basin to an open?uvial setting. We interpret our results to re?ect habitat partitioning by subregion possibly due to differential water supply.Along the Karari Ridge,the axial system and possibly marginal rivers sustained wooded environments when other subregions in the basin were beginning to show grassland spread.Higher fre-quencies of archaeological evidence in the KBS and Okote Members along the Karari Ridge have been suggested as indi-cators of home range expansion and excursions into marginal and drier habitats by early African Homo erectus(Rogers et al.,1994).If preservational differences are negligible amongst the subregions,the Karari Ridge as reconstructed by d13C values of pedogenic carbonates was a wetter and more wooded environment from2.0to1.5Ma.Rather than the hominins venturing into marginal and drier habitats,the abundance of archaeological sites and hominin paleontological material may attest to habitat preference in well-watered areas with woodland savanna and low tree-shrub grassland compo-sitions.Habitat partitioning by subregion may have created ad-ditional niche spaces for sympatric Homo and Paranthropus (Bromage and Schrenk,1995;Wood and Strait,2004)and possibly higher percentage of ecotonal boundaries between wooded and grassland environments,which may have afforded early Homo increased scavenging opportunities(after Blumen-schine,1987).Scavenging or other behaviors that resulted in greater dietary reliance on animal meat and marrow may have resulted in home range expansion(Leonard and Robert-son,2000),facilitating dispersal(Shipman and Walker,1989; Anto′n et al.,2002). Conclusions We conclude that the paleogeographic distribution of d13C values from soil carbonate from2.0e1.5Ma coincided with the path and character of the ancestral Omo River and precur-sors of Lake Turkana.Overall,the basin shifted from closed to more open savannas from2.0e1.75Ma,after which time mo-saic conditions persist.Paleoenvironmental change at Koobi Fora from 2.0e1.5Ma was ultimately related to volcano-tectonic events at w2.5Ma in the northern portion of the eastern branch of the East African Rift.Down-warping of the Turkana Basin and the associated uplift of the Ethiopian Plateau,the subsequent changes in subsidence and accommo-dation,and basin in?lling gradually transformed the basin from a lake system to a?ow-through?uvial system between 2.0to1.5Ma.As a result,there was a through-time decrease in the residence time of Omo River water in the basin and an expansion of subaerial landscapes.Climate may have served to modify or exaggerate the effects of tectonic perturbations by altering rainfall quantities delivered to the catchment areas of the ancestral Omo River.The combined effects of these phenomena caused a decrease in wooded habitats by increasing basin water loss and expanding subaerial?oodplain habitats suitable for grassland communities.Habitat fragmentation re-sulting from basin-wide evolution may have created additional niche spaces and scavenging opportunities for sympatric hominins.Based on our subregion environmental reconstruc-tions and the distribution of archaeological traces at Koobi Fora,we interpret that tool-using hominins preferred relatively more closed and well-watered environments. 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Yuretich,R.F.,1979.Modern sediments and sedimentary processes in Lake Rudolf(Lake Turkana),eastern Rift Valley,Kenya.Sedimentology26, 313e330. 573 R.L.Quinn et al./Journal of Human Evolution53(2007)560e573 浅谈自然观的形成与发展 信息工程学院 160304270213 归振翔浅谈自然观形成与发展 自然观是人对自然认知的总和，也就是人们对自然界的看法，对人和自然关系的看法。人们在想自然是什么？人们常常是从经验科学的角度来回答这个问题，多从物理生物化学的层面来解释自然。人类在不同文明阶段对人与自然关系的认识最终都可以追溯到对“自然是什么”问题的解决。然而自然观的认识大体包括人们关于自然界的本源、演化规律、结构以及人与自然的关系等方面的根本看法。自然观是世界观的组成部分，唯物主义认为自然界是不依赖人的意识而独立存在的客观物质世界。唯心主义认为自然界是精神或上帝的产物。辩证唯物主义认为自然界是处在永恒运动、变化、发展中的物质世界；自然界一切现象都是对立统一的，它们在一定条件下相互转化；自然界的发展是人类社会发展的前提和基础。我国现行的哲学和哲学史出版物，把自然观简单的划分为“朴素唯物主义的自然观”、“形而上学唯物主义的自然观”、“唯心主义的自然观”和“辩证唯物主义的自然观” [1]在原始社会，由于生产力低下，科技水平非常有限，人们的智力水平也不是很高，所以人们的认识能力也比较低。因此，人们对自然界的一些变化既不理解，又无能为力。这不能不引起人们思想上的种种迷茫，往往用虚幻的想象去填补当时经验和知识所无法回答的空白，就出现了许多神话传说。因此，在那个时代，无论是在西方还是在中国，人类所持的自然观都寓于神话或原始宗教之中。神话是远古人类对世界的起源、自然现象以及人类社会生活的初步理解，它以故事和传说的方式世代相传。在西方有《神普》和《荷马史诗》等，在中国则有《山海经》和《淮南子》等。神话或原始宗教的自然观，主张存在着超凡世界，即现实的自然界与超自然的世界的划分。任何神话和原始宗教都主张，既存在着一个包括人和社会的现实的客观自然界，又存在一个各种神和鬼魂居住的超自然世界。相信自然界存在着秩序，而且这种秩序是超自然“实体”干预的结果。在神话和原始宗教那里，自然界不是处于变幻莫测的混沌状态，而是被划分为一些明确的区域，划分为一些行动的范围。其中，每一区域和范围都由一个专门的神来统辖，从而显得井然有序，主张人能够凭借精神力量去调节和控制自然力。这是神话和原始宗教自然观的核心观念，认为人类可以通过祈祷、赞颂、占卜、祭祀、图腾崇拜等复杂的仪式活动，来达到人与神灵的沟通，并借助神力来实现自己的目的。人的力量就在于人与超自然神力恰当联系和合作，人类通过服从自然力的方式达到控制和调节自然的目的。 生活中就处处存在着自然观。在我国苏轼作为宋代多能多产、才华横溢的作家，在整个中国文学史上是一位不可多得的天才。他的自然观思想可以看作是对老庄思想的一种传承与发展。苏轼文论中的自然观表现之一是强调创作上的自然。苏轼自己说“吾文如万斛泉源， 人类的进化历程 6500万年前，一颗直径超过10公里的小行星，以每秒几十公里的速度，猛烈撞击到墨西哥的尤卡坦丰岛上。这一撞击在短时间内严重破坏了地球的环境和气候，导致全球生态系统崩溃，当时80%的生物物种惨遭灭绝，尤其是爬行动物的黄金时代结束了。地球霸主恐龙的消亡，为哺乳动物的演化和繁盛提供了契机。 5000万年前，灵长类动物呈放射状快速进化，从低级灵长类动物的原猴类中，分化出高级灵长类动物。这时候，有的猴类开始向猿类演化，原始猿类逐渐从猴类中分离出来。目前已知的最早猿类，是出土于埃及法雍的生活于3500万至3000万年前的原上猿，其次是距今2800万至2600万年前的埃及古猿。2300万年前，又演化出森林古猿，目前在非洲和亚欧大陆的很多地方，都发现有森林古猿的化石。1000万年前，森林古猿消失。 在漫长的生存过程中，森林古猿分化出了巨猿、西瓦古猿和拉玛古猿等多个分支。1400万年前，拉玛古猿开始出现，目前在非、亚、欧三大洲都发现有拉玛古猿的化石（中国云南禄丰也有发现），其共同特征是：吻部短缩，齿弓向后张开，牙齿排列紧密，犬齿小，颊齿齿冠宽短，下颌第一前臼齿为双尖型，釉质厚。这些等点与人类相似，而与猿类不同。多数学者认为，拉玛古猿是人类和猩猩的共同祖先。 1200万年前，地壳运动开始在非洲东部制造一条南北走向的大裂谷，把非洲分为东部和西部两个相对独立的动植物系统，这成为人和猿分道扬镳的关键因素。600多万年前，南北美洲还不相连，在太平洋和大西洋的中部，洋流相通；北冰洋较暖，其海水盐分较高，不易结冰。后来， 地轴倾斜角产生变化，地球接受的太阳光略微减少；地壳运动在中美洲制造了巴拿马地峡，阻断了两大洋的中部洋流；北冰洋雨水增多，其表层海水的盐分降低，较易结冰。这些因素综合在一起，使南北两极形成大冰盖；南北极的大冰盖又反射出大量的太阳光，从而使地球进入冰河期。在那冰河时代，气候严寒大量的水以冰雪的形式储存于陆地之上，海平面下降了大约50米，全球干旱少雨，地中海干涸。这时候，在非洲大裂谷的西部，由于地处赤道附近，距离大西洋不远，而且地势较低，仍然雨水充沛，森林茂密，那里的拉玛古猿栖息在大树之上，食物充足，生活悠闲，所以进化缓慢，后来逐渐演化成猩猩。与此同时，在非洲大裂谷的东部，地壳运动抬高了地势，阻断了来自遥远的大西洋本来就不太多的水汽，使那里的降雨量由西向东渐次减少，原有的大片森林退化成草原，那里的拉玛古猿无树攀援和栖息，不得不来到地面，而且食物稀少，生活艰难。为了更好地适应环境，获取食物，躲避天敌，使视野开阔，大裂谷东部的拉玛古猿开始学习直立行走。这期间，一些与现今猿类共祖的种群，因不能适应新的环境而灭绝了。500多万年前，非洲东部出现了一种双脚勉强可以行走，双手作辅助的大型高级灵长类动物，这就是南方古猿。 南方古猿，因其骨骼化石最早发现于非洲南部而得名，又称最早的人类（人属），或与其后裔的鲍氏猿人、能人和匠人一起统称为早期猿人。南方古猿的骨骼化石，主要在非洲南部和东部发现过十几处，其中最著名的当属“露西女士”。露西女士，1974年出土于埃塞俄比亚，生活在300多万年前，死亡年龄在20岁左右，全身骨骼保存率达40%。南方古猿的主要特征是：齿弓呈抛物线形，犬齿不突出，没有齿隙；脑 全球气候变化及其对人类的影响(练习) 一、选择题 1．关于全球变暖造成的影响的叙述，正确的是（） A．全球变暖不会影响社会经济生活B．全球变暖会引起海平面的上升 C．全球变暖会引起全球范围内的干旱现象D．全球变暖使得高纬度地区适宜亚热带作物生长 2．全球平均气温升高后对世界各地气候的影响是（） A．北半球高纬度和中低纬度大部分地区的降水将会减少B．热带气旋的强度和频率将会明显减少C．大部分干旱、半干旱区域则因蒸发增强变得更加干燥D．大部分热带沙漠将会消失 3．下列气体中不属于温室气体的是（） A．甲烷B．氟氯烃C．二氧化碳D．氮氧化物 4．全球变暖对生态系统的影响正确的是（） A．将改变植物群落的结构B．造成生物多样性的增加 C．物种不易患病，抗害虫袭击的能力提高D．植物的生产率会有一定幅度的降低 5．由于温室效应，全球气候有变暖的趋势，到那时，我国可能出现的情况是（）A．一月0℃等温线将移到秦岭－淮河以南B．东北山区河流春季水量比现在大 C．珠穆朗玛峰的永久性积雪冰川界线将下移D．台湾岛的面积将比现在大 6．大气中二氧化碳含量与日俱增的原因正确的是（） A．海平面的上升B．臭氧大量减少 C．燃烧煤、石油等，不断向大气排放二氧化碳和氧化氮所致D．森林被砍伐 7．大气中二氧化碳浓度含量增加将会产生的后果是（） ①海面上升②温带草原地区气候变干③腐蚀建筑物④皮肤癌发病率上升 A．①②B．①③C．①④D．②④ 8．下列关于大气环境保护的说法，正确的是（） ①全球变暖会使降水增加，农作物增产②积极开发氟利昂的代用品以及研制新型制冷系统，是保护臭氧层的有效措施③对煤炭中疏资源的综合开发利用，是减少温室气体排放的有效措施④保护大气环境，需要全球合作A．①②B．①③C．②④D．①④ 6．读“世界各大洲工业二氧化碳排放示意图”、“世界二氧化碳排放量最多的十国柱状图”及有关资料，回答：（1）图中二氧化碳排放量最多的三个大洲是＿＿＿＿＿＿、＿＿＿＿＿＿、＿＿＿＿＿＿。 （2）图中所示十国中，二氧化碳人均排放量最多的国家是＿＿＿＿，最少的亚洲国家是＿＿＿＿。 （3）二氧化碳排放量居世界第二位的国家是＿＿＿＿，其能源消费结构以＿＿＿＿＿＿为主。 （4）在工业发达国家中，二氧化碳人均排放量 法国仅为英国的52.5％、为德国的56％，从法国能源消费结构分析，其主要原因是＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿。 （5）你认为大气中二氧化碳含量增多，将会给世界沿海城市带来说明影响？＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿。 （6）要降低大气中二氧化碳浓度，你认为可以采取哪些措施？（至少写两条）＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿＿。 全球气候变化对人类活动的影响教学设计 作者：gzdili5 文章来源：本站原创点击数：18 更新时间：2006-8-15 文章属性：★★★教师活动学生活动设计说明 教学过程一、全球气候变化 引入：影片片断《后天》感受气 候变化对人类的影响。 问题： 楼兰在哪？自然条件如何？ （出示楼兰位置图，地形图，推 导楼兰的气候特点） 极盛期的楼兰是什么样的？什么 时候消失的？（简述史料，出示 想象中昔日楼兰的景象，定格楼 兰消失的年代） 问题： 楼兰文明是如何失落的？这是一 个争论了一个世纪的问题，至今 没有一个明晰的答案。有人说楼 兰的消失与全球气候变化有关， 为什么？ （展示楼兰现状图片，满目荒凉， 与昔日形成鲜明对比，显示文字 “全球气候变化!楼兰消失!两者 之间有什么关系？为什么？”） 指导学生阅读教材91页第一段 观看影片 学生继续阅读有关 材料，并回答问题， 对消失的原因进行 讨论，总结 学生阅读，利用表格 提高学生学习该节 课的兴趣 培养学生自学，独 立思考总结的能 力，了解科学研究 的方法，尝试做一 次探究。 文字，思考如下问题：全球气候变化有哪几种尺度？各种尺度上的气候是如何变化的？能否设计一个表格来表达上述问题？ 阅读91页阅读材料，了解科学家研究古代气候的常用方法。 提问：尝试用树木年轮分析法分析图4-2-2，推测该树生长时期的气候变化特点。 二、全球变化对人类活动的影响（一）全球气候变化对古代人类活动的影响 引入：唐代的兴衰史：唐代是一个温暖湿润的时期。气候的温暖湿润为唐代农业经济的发展创造了条件，农业经济的发展为社会经济的整体发展和繁荣奠定了基础。8世纪中叶气候有一个由暖转冷过程的观点，气候转寒造成了中国北方游牧民族南下压力增大，北方游牧民族纷纷入主中国北方建立区域性王朝，安史之乱是这个南下进程开始的标志性事件。经过南宋12世纪的再一次寒冷突变后，北方游牧民族则开始了入主中原建立大一统王朝的历史。（见背景资料十七） 也就说气候得便华会制约古代文概括气候变化规律。指导学生使用表 格，比较记忆，加 深印象 理论运用于实践 由例子引入，增加 学生兴趣 人类自然观的历史发展 课程名称：自然辩证法概论 上课老师：胡广丽 姓名：朱涛 学号：2012020180 学院：能源学院 人类自然观的历史发展 姓名：朱涛学号：2012020180 任课老师：胡广丽 摘要 自然观是人们对自然界的根本看法或总的观点，它既是世界观的重要组成部分，又是人们认识和改造自然的方法论。自然观的形成和发展同自然科学的萌芽、产生与发展有密切的联系[1]。要了解自然观首先要了解自然观的历史与发展。本文依次讲述了了朴素辩证法的自然观、宗教神学的自然观、近代机械论自然观、辩证唯物主义的自然观。并指出各阶段自然观的特点及意义。只有理清自然观发展的不同历史形态，对其进行全面深刻地剖析，才能揭示其本质，从而有助于人们树立科学的自然观与发展观。 关键词：自然观；宗教神学；辩证唯物主义 自然观是人们对自然界的一种认识和看法。对自然界的看法主要受两个因素的限制：一是受到生产力发展水平的限制，二是受到和生产力相应的科学水平的限制。在这两个因素之中，生产力因素是最基本的，因为对自然界的认识要通过科学来实现，而科学的发生和发展是由生产力决定的[2]。它的产生、发展源远流长。不同的人有不同的自然观，不同时期人类自然观也不同 一、朴素辩证法自然观 古希腊自然哲学的最初尝试，是想用一种理性的方式取代传统的神秘主义来对自然界中所发生的一切事件做出解释[3]。我们把16世纪以前的科学技术统称为古代科学技术，与之相适应的是古代朴素辩证法自然观。古代朴素辩证自然观认为万物有共同的组成成分，肯定了自然界的物质性和统一性，把精神看作是物质的派生物。古代朴素自然观从整体上对自然界的本质和规律做直观的考察，论述了自然界事物相互联系、相互作用的辩证法，提出了对立面的统一和斗争是世界万物发展变化的内在原因，提供了一幅自然界的总图景。但它也有历史局限：它在直观的基础上，运用理性思维，对自然现象进行笼统的、粗糙的哲学概括。表现出直观性、思辩性和猜测性等历史局限性。 古代朴素辩证法自然观的基本特点：古代自然观最显著的特点是，从整体上对自然界的本质和规律作直观的考察，勾画了自然界的总画面。它肯定了自然界的物质性和统一性，论述了自然界事物相互联系、相互作用的辩证法，提出了对立面的统一和斗争的思想。这些基本观点在本质上是正确的。具体地说，古代自然观对自然界的认识具有以下特点：第一，力求简单；第二，认为万物的本原是连续性和间断性的物质；第三，整体直观性；第四，富于想象；第五，深信和谐；第六，相信守恒；第七，合乎常识[4]。 古代自然观具有极其重要的历史地位。概括起来，第一，标志着人类对自然界的认识已冲破原始神话和宗教的藩篱，开始运用理性思维去探索自然的本质和规律，这是人类在认识自然的道路上的一次巨大进步。第二，意味着哲学与自然科学之间存在着天然的联系：一方面哲学要以对自然界的认识作为自己的重要基础；另一方面自然科学在认识自然界的过程中不可能回避对自然界总的观点的问 鲁教版必修一第四单元 第三节全球气候变化及其对人类的影响教学案课前学生结合导学案自主预习。 导入：一段2分钟的“全球气候变暖的现象例证”的视频导入——感知、认识全球气候变暖 教师提升：对于“全球气候变化及其对人类的影响”我们的研究思路应该是什么？ 学生答：略 教师承转：全球气候一直在变暖吗？如果没有，那是怎样变化的？ 学生答：略 一．全球气候变化的过程、特点 教师问：按时间尺度，全球气候变化分为哪几个时期？ 学生答：略 PPT展示“地质时期的气候变化”图、“历史时期全球年平均气候变化曲线”图、“近百年来全球年平均气温变化曲线”图。学生读图回答： 1、地质时期的气候变化图中出现了几次寒冷的大冰期？ 2、地质时期气候变化特点是什么？ 3、历史时期气候变化特点是什么？ 4、仪器观测时期气候变化特点是什么？ 5、哪两个时期气温上升较快？ 6、图中从1860—2000年气温大概上升了多少度？ 教师总结提升：活动一——目前全球气候变暖： A——是全球气候变化的一种正常体现? B——还是人类活动所导致？ 二．全球气候变暖的原因 PPT展示四种温室气体在大气中随时间的含量变化示意图、近百年来的世界平均气温变化图、2002年中国与世界能源消费结构 学生活动：总结全球气候变暖的原因。 承转：“全球气候变暖的影响”视频播放 三．全球气候变暖的影响 教师问：结合昨天的预习和观看的视频，全球气候变暖的影响有哪些？ 学生答：略 教师承转：这是全球气候变暖的四个大的方面的影响，下面我们就两个方面展开探讨。 活动二：全球变暖后，海平面上升了，会引起… 小组合作请将下列选项“对号入座”对号入座： A 海水受热膨胀 B 海平面上升 C 海水入侵 D 低地淹没 E 海岸侵蚀加强 F 土地盐碱化 G 冰川融化 H 海岸线退缩 I 地下水位上升 J 海岸工程建设破坏 K 风暴潮、洪涝等自然灾害加剧 材料一：《中国海洋报》报道2004年～2006年，中国沿海大多数地区沿海海平面都高于常年。 受海平面上升影响，上海沿海地区的咸潮入侵和海岸侵蚀等海洋灾害都有所加重。另外，咸潮频繁入侵，对城市供水造成影响，地下水和土壤盐渍化加重，严重危害上海的水资源环境和生态环境；海平面上升使浙江沿海风暴潮灾害更加严重，2004—2006年间，有5 次灾害性台风先后在浙江登陆；2006年海南沿海海平面比常年高107毫米，沿海部分岸段侵蚀严重，其中海口市因海岸侵蚀损失土地约1.5平方公里，海滨旅游区和海岸工程设施受到威胁。 活动三： C 4.2 全球气候变化对人类活动的影响 学案（湘教版必修1） [学习目标] 1.运用资料说明地质时期、历史时期和近现代气候变化的特点。2.举例说明全球气候变化对人类活动的影响。3.学会运用图表资料分析气候变化特点，并能提出相应对策。 一、全球气候变化 1 时间 气候变化规律 地质时期 1万年以前 ①____________________交替出现 历史时期 近1万年来 ②________________________交替出现 近现代 一二百年 全球平均地表温度呈上升趋势 2.基本概念??????? 冰期：指地质历史上气候寒冷、③ 广泛发育 的时期 间冰期：指两个冰期之间气候比较④ 时期雪线：指常年积雪的下界，即年降雪量和⑤ 相等的平衡线 冰盖：又称冰原，指覆盖在各种地形上的⑥ ，由多年冰雪堆积挤压而成。目前尚存的有南极冰盖和⑦ 冰盖等 3．气候变化史 (1)地质时期的气候变化：处于⑧____________之中，冷暖干湿相互交替；变化周期长短不一。温 暖期较长，寒冷期偏短；湿润期与干旱期相互交替，新生代以⑨________期为主。 (2)历史时期的气候变化：全球气候有⑩____次较大的波动。一次是公元前5 000年至公元前1 500年的?________期，当时年均气温比现在高3 ℃～4 ℃；另一次是15世纪以来的寒冷期，年均气温比现在低1 ℃～2 ℃。 (3)近现代的气候变化 a ．总体特点：全球平均地表温度呈?____________的趋势。 b ．地区特点：北半球中高纬地区和热带地区降水量增加，?____________地区降水量减少。 c ．直接影响：导致雪盖、?________面积减少，全球海平面?________。 二、全球气候变化的影响 1．资源条件发生变化，增加了人类开发利用自然资源的?________。 2．加剧了?____________。 3．导致?________________的改变。 4．显著影响?________、林业、牧业、渔业等主要生产领域。 5．通过极端天气和气候事件，扩大某些?________的流行，危害人体健康。 探究点一 全球气候变化 【探究材料】 2008年2月28日，中国首次大学生考察队从北京出发，前往挪威斯瓦尔巴群岛进行为期半个月的考察。 材料一 “冰雪之都”奥斯陆以前2月的平均气温是－2 ℃，而2008年2月的极端最低气温仅为－2 ℃～－3 ℃；2007年的几个星期，从挪威海域通过北冰洋，再到白令海峡，出现的无冰地带，比前些年同期宽了不少。 材料二 北极熊的栖息地日益减少；冰鸥、贼鸥等极地动物在近20年中数量锐减；北极熊体内积累的多氯联苯等物质使其免疫力、繁育能力每况愈下。在考察期间队员们没有见到一只北极熊。 1．写出图中数字所代表的国家名称：①________，②________。 2．北极熊的数量明显减少，造成这种现象的原因有( ) ①全球气候变暖造成其生存环境明显恶化 ②海水变得越来越咸导致饮用水源缺乏 ③有毒的污染物通过食物链富集危害其健康 ④考察队员使用的交通工具产生的噪音危害其生存 A ．①② B．③④ C．②④ D．①③ 3．根据材料，考察队员获取全球变暖的证据是__________________； ________________________________________________________________________。 4．为了应对全球变暖，1997年《京都议定书》提出要减少二氧化碳的排放量；2001年《波恩协议》又提出可以用增加森林植被来抵消二氧化碳的排放指标，提出这项决定的依据是 ________________________________________________________________________。 5．全球气候变化就是全球变暖，是由人为原因造成的，此说法是否正确？为什么？ 第四章自然环境对人类活动的影响 全球气候变化对人类活动的影响【教学目标】 知识目标 通过学生分析相关资料说明全球气候变化的三种尺度和特征。 通过学生阅读课本资料来了解科学家推测古代气候状况的方法。 通过学生通过历史知识分析全球气候变化对人类古代文明和经济活动以及生态环境的影响。能力目标 通过学生阅读资料，培养学生的收集、处理信息的能力，培养学生的自学能力。 通过“中国古代气候变化及其对人类活动的影响”的图表分析，提高学生的读图、析图能力。通过探究活动开阔学生思维，提高他们的动手能力。 情感目标 使学生认识到人类社会现在和未来的生存与发展跟气候有密切关系。 提高学生对生态环境的保护意识，确立走可持续发展的道路。 【教学重点】 全球气候变化对近代人类活动的影响。 【教学难点】利用资料分析、总结全球气候变化的特点及对人类活动的影响。 【课时安排】一课时 【教学手段】多媒体教学组织分析材料 【教学过程】 【导入】同学们！你们知道我国历史上的楼兰古国吗，下面我们来了解一段有关楼兰的材料。录音及图片 到目前为止，也没有弄清楼兰消失的确切原因，但大多数研究人员都认为与气候变化有关。那全球气候怎样变化呢？ 同学们阅课本91页第一段回答：气候变化的时间尺度有哪几种？ 地质时期的气候、历史时期的气候、近代气候 由以上内容可以看出全球气候一直是在变化中的 承转：那么科学家是怎样推测古代气候变化的呢？ 阅读科学家是如何推测古代气候状况的 尝试用树木年轮分析法分析图4-2-2 该树生长时期的气候变化特点？ 设问：由以上内容气候变化影响了树木生长的快慢，那么全球气候的变化对人类活动有没有影响呢？ [板书]全球变化对人类活动的影响 看图4-2-3分析图的含义： 横坐标表示时间变化右纵坐标表示中国年平均气温左纵坐标表示挪威雪线高度知识与技能何为雪线？？？ 图中蓝虚线为挪威1万年来的雪线升降图 红实线为中国近5000年年平均气温变化曲线 观察二者变化趋势有什么关系？ 人类的进化历程有哪些详细过程? 在地球生物圈中,物质和意识组成我们这一现实世界,组成了地球生物进化文明的序幕,使得我们这一现实世界五彩缤粉。 在当代人类的眼里,科学与文明是一盏不可分割的神灯,它带给人类那么多不可思议的东西,1945年7月16日,第一颗原子弹在美国试爆成功,爆炸力相当于两万吨TNT炸药。同年8月6日和9日两颗原子弹分别投向日本的广岛和长崎,使两个城市瞬间化为废墟,举世震惊。1957年10月4日苏联成功地发射第一颗人造地球卫星,宣告了航天时代的到来。1969年7月美国的阿波罗号飞船将两名美国宇航员送上月球,第一次实现了数千年来月亮旅行之梦。1945年底,世界上第一台电子管电子计算机在美国问世,1948年美国贝尔实验室发现晶体管后,电子计算机以惊人的速度发展,每5年运算速度提高10倍,体积和成本降低10倍,把人类带入了电脑化时代。 20世纪的科技的发展造就了人类前所未有的征服和改造自然的巨大生产力,创造出文明史上最为辉煌的伟大奇迹。在物质领域,高分子化学材料、生物技术、遗传工程、新型建筑材料、先进的交通工具和通讯技术等;在意识领域,科学文化、教育、艺术均步入电脑时代,都在点缀着现代生活的方方面面。 面对这异彩纷呈的物质、意识文明,人类不禁会产生这一个信念,科学文明简直是万能的,它会有什么做不了的事情呢?如果它现在无能为力,那肯定是因为它还不发达,只要继续发展科学文明,人类征服自然和改造自然的能力就会越来越强,人类的生活就会越来越美好。 然而,在科学文明成功的背后,人类已经看到一个无比强大的潜在危险正在显露出来,1987年7月11日,南斯拉夫的萨格勒布市的一名叫特伊.加斯帕尔的男婴降生了,这事引起全世界的特别关注,连当时任联合国秘书长的德奎利亚尔先生也专程赶到医院探望。事情的关键并非由于这个男婴自身有什么独特之处,而是因为,他是地球上的第50亿位居民。50亿,也许算不得什么惊人的天文数字,但对地球来说,不啻于足球场上亮出一枚黄牌,50亿人口,对地球生物圈环境而言,的确是一声洪钟般的警告。到了1997年,人类的人口已近60亿;据联合国环境规划署等机构预测今后50 年内,世界人口可能翻一翻,大大突破百亿人口大关,这意味着人类将面临生存与毁灭的严峻挑战。 人口的增长也意味着物质、意识领域的同步均衡增长,人类通过更大规模的开发利用地球自然,掌握更高的能量,支配自然,从而满足人类不断增长的人口数量。但地球都是一个相对封闭的生物圈,既无法承受人类掠夺性的野蛮破坏,同时,最终也破坏人类自身生存的根基。 现代工业和现代生活所需的能源绝大部分来自煤、石、油和天然气,这是地球在演变过程中花了近30亿年积攒下的非再生能源,以目前的开采速度,在一个不远的将来,也许在我们的有生之年,将被彻底耗光。到那时候没有新能源供应,氧化文明社会就会土崩瓦解。可是环境呢?地球是否会回到30亿年前的原始荒芜的恶劣的自然环境下呢?空气中缺乏氧气, 二氧化碳可能成为超过氧气的主要气体,碳氢、碳氧、氧化氮、氧化硫等化合物的有毒气体会窒息地充满在大气层内。由于工业、农业的污染,大量含氯类的工业及消费品的排放,将彻底破坏大气层中的臭氧层, 紫外线将长驱直入地杀伤地球生命。同时大气在失去臭氧层的情况下, 会失去保温层的作用,昼夜的温差变化极大,狂风暴雨,炎热干旱酷暑严寒将扫荡 气候变化对自然和人类社会系统的影响 —— IPCC 第三次气候变化评价报告;第二工作组报告概要 政府间气候变化专门委员会(IPCC 第二工作组于 2001 年 2 月 13~16 日在日内瓦召开了第六次会议, 就气候变化的影响、系统的脆弱性以及适应能力等问题通过了该工作组提供给决策者参考的第三次气候变化评价报告概要。 1. 最新研究结果 1.1 近期的区域气候变化特别是温度升高已经对生物物理系统产生了影响 (1观测表明,区域气候变化对全球许多地区物理的和生物的系统产生了影响,包括:冰川的退缩、冻土的融化、河湖冰的迟冻和早融、中高纬生长季节的延长、动植物范围向极区和高海拔区延伸、某些动植物数量的减少以及开花期、昆虫出现和鸟儿产卵的提前等 (2降雨变化的影响也很重要,但目前因缺乏足够长的数据序列还无法分析其影响。 (3土地利用变化与污染等因素也对生物物理系统产生影响,但在特定个例中很难区分出各个因素影响的程度。 1.2 初步研究表明, 一些人类社会系统受到了近期频繁发生的旱涝的影响有证据表明, 一些地区的社会和经济系统已经受到了近期频繁发生的洪涝和干旱的影响, 这些系统也同时受到社会经济因子如人口增长的影响,一般来说很难将气候和社会经济因子的相对影响定量区分。 1.3 自然系统对气候变化极其脆弱, 有些系统将遭受不可恢复的破坏自然系统由于其有限的适应能力而对气候变化表现出特别脆弱的特征, 其中一些系统可能遭受严重的、甚至不可恢复的破坏。正在面临这种危险的系统包括:冰川、珊瑚礁岛、红树林、北半球北部山区、热带林、极地和高山生态系统、草原湿地、残余天然 草地。随着气候变化频率和幅度的增加, 受影响系统的数目及遭受破坏的地理范围也将增加。 1.4 许多人类社会系统对气候变化反应敏感, 其中一些比较脆弱对气候变化反应敏感的人类社会系统主要有:水资源, 农业 (特别是粮食保障系统和林业, 海岸带和海洋系统 (渔业 , 人类居住、能源和工业, 保险与其它金融系统以及人类健康。这些系统的脆弱性随其地理位置、时间以及社会经济和环境条件而变化。 不利影响包括: (1对于多数的温度升高预测结果,大部分热带和亚热带区存在着普遍的作物减产可能; (2对于平均温度升高大于几度的情况,多数中纬度地区存在着普遍的作物减产可能; (3对许多缺水地区的居民来说,水的有效利用降低,特别是亚热带区。 (4受到传染性疾病影响的人口数量增加,热死亡人数也将增加; (5大暴雨事件和海平面升高引起的洪涝对许多居住区的危险性普遍增加 (6由于夏季高温降温而导致能源需求增加。 有利影响包括: (1温度升高低于几度的情况,中纬度的一些地区存在着作物增产的可能; (2全球木材供应可能会增加; (3对某些缺水地区的居民来讲,可用水量可能增加,如在东南亚的部分地区; (4中高纬度地区居民的冬季死亡率降低; (5由于冬季高温,取暖所需能源减少。 全球气候变化及其对人类的影响 编制人审核人 班级小组姓名 必修一第四单元第三节 全球气候变化及其对人类的影响 【学习目标】 【知识目标】 1.了解不同时期的全球气候变化，及引起气候变化的原因 2.理解全球气候变暖的原因及影响，理解人类活动对全球气候变暖的影响。 3.面对全球气候变暖的趋势，我们应采取那些措施。 【技能目标】 利用不同图表资料分析气候变暖的原因及其对人类的影响，并提出有效措施。 【情感目标】 通过正确认识全球变暖原因影响，树立节能减排保护环境的意识，增强社会责任感和主人翁意识。 【过程与方法】 1、结合历史知识，分析气候变化与古代文明兴衰的关系。 2、收集、分析、整理相关资料，了解全球变暖的影响。 【重难点】 1、正确认识全球变暖原因 2、理解全球变暖的影响、措施 【课时】1 【学法指导】 注意深入思考学案中每一个问题，循序渐进，探究过程尽量自己独立完成，不要只记最后的结果，疑惑点可以与同学探讨； 【学习过程】 【情景设置】教材引言 一、过去的全球气候变化 探究一.阅读教材，结合图4-3-2，过去的全球气候 变化的情况。 （1）你认为哪些因素能引起全球气候变化？ 、、、 （2）研究过去气候变化通常划分哪几个时期？ 、、 （3）读图4-3-2，你能总结出15万年以来地球气候变化的特点吗？ ①、“地质时期”的气候变化，表现为期和期交替， 大致以年为周期。冰期时，冰川从向，从向推进，气候 明显变；间冰期时冰 课前评价ABCD课后评价ABCD 川，气候变。当前地球气候正处于中。 ②、“人类历史时期”的气候也发生过显著变化， 大量史料表明，500年来我国气候的变化表现为15、17、19世纪的期和16、18、20世纪的期交替出现。 ③、百余年来，仪器观测时期的全球气温变化，也 是冷暖交替，19世纪末到20世纪40年代，是时期；从20世纪初到20世纪____年代全球气候逐渐_____，此后30多年全球气候有所变____，从20世纪____年代末开始，全球气温又逐步______，并呈现加速态势。 【自我小结】对该部分内容做个自我总结吧： 过去全球气候处于不停的中，全球气候受多种因素 影响很复杂，如受、、、等因素影响。地质时期的气候 变化状况总体表现为的期和的期交替，当前地球气候正 处于的期。 二、全球气候变暖的原因 探究二：气候变暖是近现代气候变化的主要特征， 原因是什么呢？阅读教材结合图4-3-3思考： 1、二十世纪50年代以来全球二氧化碳含量有何变 化趋势？同期全球气温有何变化趋势?特别是（时间）以 第二节全球气候变化对人类活动的影响 从容说课 本节教学的主要内容包括全球气候的变化及全球气候变化的影响。 在“全球气候变化”的教学中，要使学生明白全球气候在不断变化中，其变化主要通过气温、降水、风等要素的变化来度量，教材列举了不同时间尺度的气候变化情况，这是本节课教学的重点。为此教材提供了大量的图示信息及相关问题，以培养学生分析问题、解决问题的能力。 “全球气候变化的影响”的重点在“影响”上，而有些影响可能尚未发生，是预测性的。教材中主要讲了以下五个方面的可能影响：全球气候变化本身是资源条件的变化；全球气候变化加剧了自然灾害；全球气候变化将导致原有生态系统的改变；全球气候变化对农业、林业、牧业、渔业等部门的影响；全球气候变化对人体健康造成危害。围绕这些内容，教材还设计了一个“活动”，以增强思考性和实证性。教学中，教师一方面需要扩展教学内容，另一方面还要提供图示、图表信息，让学生自主探究。 教学重点1.全球气候的变化。 2.全球气候变化的影响。 教学难点1.历史时期及近现代的气候变化。 2.全球气候变化对人类的生产、生活产生的重大影响。 教具准备多媒体课件、挂图、投影图片等。 课时安排1课时。 三维目标 一、知识与技能 1.通过资料认识全球气候一直处于波动变化之中并呈现出一定的变化周期。 2.理解全球气候变化对人类的生产、生活产生的重大影响。 3.掌握阅读、分析、运用地理图表和地理数据的技能。 二、过程与方法 1.初步学会通过多种途径、运用多种手段收集有关的气候资料，并将气候变化资料进行整理分析运用在地理学习过程中。 2.尝试运用所学的知识和技能整理、分析有关气候变化的信息。 三、情感态度与价值观 1.培养学生尊重自然规律积极地适应自然规律并在尊重自然规律的前提下改造自然。 2.激发学生探究地理问题的兴趣和动机，提高地理审美情趣。 教学过程 导入新课 师：请看下面的网页新闻和材料。你认为导致图瓦卢的岛屿完全被海水淹没的原因是什么？ 投影： 图片和材料 人类的自然观和世界观的演变经历了一个漫长和艰辛的过程，整个自然观的演化史，也是整个人类文明的进化史。科学技术，一直在加速改变人类对世界的认识，时至今日，已经成了改变我们对世界认识的主要推动力。 纵观整个世界史，最早的，被公认的高度发展的文明，就是古埃及，古巴比伦，古印度以及我们的中华文明。这四大古文明都代表了那个时期，世界各个地域的最先进的，最具代表性的思想。任何的文明，任何的哲学都必然面临三个终极的问题。我是谁，我来自哪里，我将要去何处。高度的文明，就是人和动物的本质的区别。下面我们先罗列四大古文明的创世观观，再对其进行分析。 首先古埃及人人文最初的世界是一片黑暗的原始之水“努恩”，后来在水中升出第一块陆地，原始之丘。其上荒凉晦暗，长满原始植物。就在这晦暗的土丘上，诞生了“阿图姆”神。之后，阿图姆神生下空气之神“殊”和潮气之神“特弗努特”这对兄妹，这对兄妹神结合生下天后“努特”与地父“盖伯”。天地诞生，世界出现。“奔奔石”模仿的就是世界创造之初的原始之丘，法老的陵墓之所以修建成金字塔的形状，其根本原因也在于此。都是对创世的模仿。古埃及人认为，永恒是一个不断的循环，但这个循环不是原封不动的重复，而是再生，是突破了旧的束缚的创造。 古印度人的创世观也是很有意思的。他们认为在地面之下，有力大无穷的四只大象支撑著，大象则站在象征力量的乌龟的背上，乌龟又趴在首尾相衔的眼镜蛇背上。一些印度民间神话也这样描述：蛇神舍沙环绕着龟神俱利摩，支撑起负责背负整个世界的四头（或称八头）大象。著名的奇幻小说作家Terry Pratchett 巧妙的借鉴了这个创世观的设定，创作了“碟形世界”这个著名的系列小说。 古巴比伦人认为太古之初，世界一片混沌，没有天，没有地，只有汪洋一片海。海中有一股咸水，叫提亚玛特，还有一股甜水，叫阿普苏，它们分别代表阴阳两性，在汪洋中不断交汇，生出几个神祗。然后众神大战，最后的胜利者建立了伟大的巴比伦王国。 对于我们中国的创世观，大家都非常熟悉，天圆地方，盘古开天，女娲造人。但是中国后来的自然观，受到了儒道佛三家的相互影响，这也是中国文化发展的一大特色。 公元之前的几千年，我们可以明显的看出，那个时候的自然观都是非常的朴素。大多深受当地的气候，地域的影响。例如古埃及，我们可以看出，循环与永恒的‘彼岸说’，是深受尼罗河的影响。这种创世观，深深的影响了古埃及的文化，政治，艺术等各个方面。两河文明则让我们看到了波斯湾和淡水对于中东地区产生的重要影响。而地处热带与亚热带的印度，大象和乌龟则直接被古印度人用来理解并解释世界。后来的佛教则发展出了一套非常完善的理论体系，“因果论”“轮回说”则深深的影响到了后来的中国。这个时期，人们对天和地，生和死，都是具有一种出于未知恐惧的敬畏。所以“彼岸说”，“轮回说”是当时的主流普世价值观。科学技术对于人们的影响太小，人们只能靠着自己对周围见闻的理解，做出最朴素的解释。 公元标志着一个新的纪元的来到，西方的哲学与科技有了长足的进步。几何学，代数学的诞生为以后的数学以及自然科学的发展奠定了坚实的理论基础。科学技术渐渐的展示了它对于人类认识世界的重要性。但是这个时候对人们自然观和世界观起决定性影响的仍旧不是科学技术，而是宗教。基督教，伊斯兰教和佛教，这三个世界上最大的宗教都在公元前后诞生。这三个宗教都是在各自的文化背景下淬炼的产物。三者都有自己各自的价值观体系，互相独立，但是又有千丝万缕的联系。基督教笃信的是上帝，相信人类是亚当夏娃的后代，行善者死后去往天堂，作恶者死后去往地狱。伊斯兰教则更强调的是现世，真主安拉则是一切的本源。佛教讲求的是修行和因缘，功德圆满，立地成佛，生平作恶，则要下地狱，六道轮回，不生不灭。这个时候人们的自然观更多的是被统治者以宗教的形式进行引导。宗教成了 人类进化的过程 上文阐述什么原因造成人类进化与起源——“人，多种能源的使用者”。下面我就人类进化的特殊道路进行描述。 因为生命是在时间周期内熵值呈现周期变化耗散体系。不断地吸收周围能量是生物的本能活动。科学界所共识“进化是由于气候的原因”，而人类以外的物种其进化方式是被动的适应周围环境与气候，所以人以外的生物其智力进化与其身体其他器官进化是同步进行的，而当环境与周围竞争相对稳定后，大脑与其他身体器官的进化日渐缓慢。除人以外动物进化曲线可以为： 但是人类不同于其他生物在于进化过程中不但本能利用几种特定生物能量，还超出身体机能使用周边其他能源。这里我就要提出一个新概念——辅助进化。辅助进化就是利用自然界物质而非本体器官间接获得能源的方式。辅助进化是由于人类利用能量种类、量级、效率的增加，而带来超出自身器官功能可以处理信息量的非本能的转化过程。同时，辅助进化的产生不但使得人类走向不同于其他动物的进化道路，也成为自有语言产生以后人类进化的主要手段，从远古直到现代，甚至可以预见的不远未来。 “火的使用”是生物界第一次不利用自身新城代谢的方式把自然界的能源转化为可控能，从而使自身的熵值负化的过程。正是由于货的使用导致的多信息在没有身体基因遗传的基础 上语言产生才有最大的可能性与必要性。虽然开始阶段火的使用可能是无意中进行。可是以后保留火种的行为是人类走上特殊进化的标志，至此以后的用火照明等活动与以前的所有动物都不同了。因为这时人猿开始从大自然索取能量方式中使用非自身代谢的能量而改变自身的熵值使自身有序化，从被动进化、被动适应环境，而转入主动进化、主动的使环境适应自身的生理条件。从而使人类整个智力的进化曲线发生了改变。人类的智力改变也由上图变为下图状态。这几个折线的节点风别代表：人类使用能源的种类增加与是利用能源效率的增加。 由上图可以看出来人类群体智力的进化过程中，辅助进化的表现与能量的使用种类增加与使用能源输入效率的增加是一致的，而且辅助进化在人类群体活动出现组织不同个体分工后，其表现为组织整体的进化方式更为突出，比如：近代人类的一个国家或一个地区其科技水平超出其他地区的现象就是辅助进化在人类社会的表现。 下面我就描绘一下人类进化全过程。 第1步、第一次非自身新陈代谢能源的使用——火的使用 由于气候与地理条件的变化，古猿失去了森林生活的条件，转而向森林与草原的过度地带生活。为了适应树木与草原的同时生活，一群古猿被迫—“直立行走”就此产生。从而诞生了一个新种—“直立人种”。这样古猿直立人种既可以从树上取食，又可以在草原上奔跑 全球气候变化对人类活动的影响 一、选择题 (高考海南卷)全球变暖已经成为全世界共同面临的问题，但就升温幅度而言，北半球比南半球大，高纬度地区一般比低纬度地区大。据此回答1～2题。 1．下列四地中升温幅度最大的是() A．蒙古高原B．亚马孙平原 C．巴西高原D．长江中下游平原 2．南北半球升温差异的最主要原因是() A．大气成分的差异 B．海陆分布的差异 C．太阳辐射的差异 D．大洋环流的差异 解析：第1题，从材料中可知，北半球纬度较高的地区升温幅度可能最大，四个选项中最符合的是蒙古高原。第2题，北半球陆地所占比重较大，因陆地比热容较小，升温速度快，该半球升温幅度较大；而南半球以海洋为主，因海洋比热容较大，升温速度慢，故该半球升温幅度较小。 答案：1.A 2.B (2017·高考天津卷)读图文材料，回答第3题。 全球变暖导致的环境变化越来越引人关注。地理小组的学生将上图中近十几年来(阴影所示)相关数据的变化趋势与以前进行了比较。 3．学生经比较后得出的结论，与上图所示信息相符的是() A．海洋表面增温趋缓，海平面减速上升 B．地球表面增温趋缓，海平面仍在上升 C．火山喷发频率增加，海平面加速上升 D．800米以下海洋储热量增加，海平面减速上升 解析：选B。读图可知，近十几年来，年平均海面温度变化曲线呈波动变化的趋势，说明海洋表面增温趋缓，但海平面的上升速度并没有明显变化，选项A错误；近十几年来， 年平均陆面温度和海面温度变化曲线呈波动变化的趋势，说明地球表面增温趋缓，但海平面仍在以一定速度上升，选项B正确；近十几年来，并没有集中发生火山喷发事件，且海平面的上升速度并没有明显变化，选项C错误；近十几年来，800米以下海洋储热量增加，但海平面的上升速度并没有明显变化，选项D错误。 (2020·长沙长郡中学调研)随着时间的推移和环境的变迁，受气候变暖、降水增减、病虫害增多、人口增长、土地利用、森林火灾、灯光干扰等因素影响，老弱植物在原区域枯死，原有植物在新的区域发展，种群中心发生转移。研究发现，北美东部地区的裸子针叶植物如云杉、冷杉、松树，数十年来每十年向北迁移11 km；喜高温和雨水的开花被子植物如白橡树、糖枫树、冬青属植物约有3/4 每十年向西迁移15.4 km，没有出现东迁或南迁现象。据此回答4～6题。 4．北美东部地区的裸子针叶植物种群中心北迁的影响因素主要是() A．热量B．水分 C．光照D．土壤 5．北美开花被子植物种群中心向西迁移，可能是因当地() A．年均温降低B．蒸发量减少 C．自然灾害减少D．土地开发利用 6．北美开花被子植物种群中心西移的速度快于裸子针叶植物种群中心北迁的速度，这说明() A．病虫害对东西方向的影响小于南北方向 B．水分变化大于热量变化 C．人类活动在东西方向的影响大于南北方向 D．热量变化大于水分变化 解析：第4题，裸子针叶植物能够耐寒，一般生长在较寒冷的环境里。北美东部地区的裸子针叶植物种群中心北迁主要说明了全球气候变暖影响其生长环境。热量增加会关闭气孔以减少蒸发，但也会失去光合作用，故会导致其死亡，即使不死亡，其防御性也会降低，纬度越高气温越低，故向北迁去寻找新的生长环境，其影响的主要因素是热量，A对。第5题，气候变暖使得美国东部的温度升高，蒸发量更强，故A、B错；美国东部地区人口密集、土地使用的变化、森林火灾的发生频率、害虫或者灯光都可能会影响树木分布，故C错，D 对。第6题，北美开花被子植物种群中心西移的速度快于裸子针叶植物种群中心北迁的速度，结合上题分析可知西迁主要与人为因素影响有关，而北迁主要是全球气候变暖即自然因素引起，故C对。 答案：4.A 5.D 6.C (2020·晋江四校模拟)下图示意新疆天山乌鲁木齐河源1号冰川地区1960－2010年气候、冰川零平衡线(冰川零平衡线是冰川积累区和消融区的界线，在零平衡线上，冰川的积累和浅谈自然观形成与发展
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