Climatic cycles and behavioural revolutions: the emergence of modern humans and the beginning of farming.

Climatic cycles and behavioural revolutions: the emergence of modern humans and the beginning of farming. Publication of a new volume on the beginnings of Old World farming(Harris 1996) has provided a compendium of current views on thiscritical inflection-point in human inhabitance of the world. Was itdriven by climatic change Climatic Change is a journal published by Springer.[1] Climatic Change is dedicated to the totality of the problem of climatic variability and change - its descriptions, causes, implications and interactions among these. , as Gordon Childe suggested? And what of theearlier emergence of modern human behaviour: were these two chapters inthe same story?Punctuation is back in fashion; not sophistication so��phis��ti��cate?v. so��phis��ti��cat��ed, so��phis��ti��cat��ing, so��phis��ti��catesv.tr.1. To cause to become less natural, especially to make less naive and more worldly.2. in the use of thesemi-colon, but the idea of rapid, revolutionary change. After years ofbeing described (in feeble imitation of Lord Acton's description ofthe Holy Roman Empire Holy Roman Empire,designation for the political entity that originated at the coronation as emperor (962) of the German king Otto I and endured until the renunciation (1806) of the imperial title by Francis II. ) as `neither Neolithic, nor a revolution'(1),the beginnings of farming are increasingly being attributed to a short,sharp shock at the end of the Pleistocene, known as the Younger Dryas(2)event (Moore & Hillman Hillman was a famous British automobile marque, manufactured by the Rootes Group. It was based in Ryton-on-Dunsmore, near Coventry, England, from 1907 to 1976. Before 1907 the company had built bicycles. 1992; Bar-Yosef & Belfer-Cohen 1992). Atan earlier date, the emergence of modern humans is also coming to beseen, not as a protracted evolutionary process, but as a HumanRevolution (Mellars & Stringer 1989). In fact, the everyday (andetymologically justified) usage of the term `evolutionary' -- agradual unfolding, by contrast with `revolutionary' -- is now atodds with biological usage, where punctuated evolution has been arespectable, if not universally espoused, concept for 25 years (Eldredge& Gould 1972; Gould & Eldredge 1977). These two features,evolutionary punctuation and climatic instability, seem to be closelyrelated; and they form part of a new picture of rapidly changingPleistocene environments. Chronological resolution and the speed of changePunctuality PunctualityFogg, Phileascompletes world circuit at exact minute he wagered he would. [Fr. Lit.: Around the World in Eighty Days]Gilbrethsdisciplined family brought up to abide by strict, punctual standards. [Am. Lit. requires precision. With the old-fashioned kind ofevolution, chronological questions could be fudged: if farming andmodern humanity were (as J.L. Myres described the Greeks) `ever inprocess of becoming', there was little need for a precisetimetable. With a punctuated model, accurate dating is essential.Fortunately, the relevant parts of the timescale are improving both inaccuracy (allowing the correlation of different forms of evidence) andprecision (aiding the identification of rapid changes). First, accuracy.The tree-ring calibrations of radiocarbon currently reach back only toc. 9500 BC, before which the less precise marine carbonates must be used(Bard et al. 1993; Edwards et al. 1993; Stuiver & Reimer 1993; Bard& Kromer 1995; Kromer et al. 1995). Even these, however, haveradically shaken up our expectations: whereas calibration has addedroughly a millennium to `raw' radiocarbon dates in the earlier partof the Holocene, the marine carbonate curve suggests that approximatelytwo millennia need to be added to radiocarbon determinations before10,000 b.p., and that before 12,000 b.p. the difference is perhapsnearer 3000 years -- beyond which the curve may diverge stillfurther.(3) Since this puts the peak of the last glaciation at some timearound 20-21,000 years ago (instead of 18,000 b.p.), this has importantimplications for climatic modellers, who increasingly rely on theMilankovitch curves (Imbrie & Imbrie 1986) to calculate variationsin solar budget of different parts of the world, and so reconstructparameters of climatic change (Kutzbach in Wright et al. 1994),providing a long-term environmental chronology.(4) Because thesecalculations are naturally done in 'real' (solar) years, it isimperative that the geological community -- hitherto the most reluctantto use anything other than unaltered radiocarbon estimates (andperversely calling them `BP' rather than `b.p.') -- should nowroutinely think in terms of calibrated dates; otherwise theirempirically determined warm and cold phases in the late Pleistocene The Late Pleistocene (also known as Upper Pleistocene or the Tarantian) is a stage of the Pleistocene Epoch. The beginning of the stage is defined by the base of Eemian interglacial phase before final glacial episode of Pleistocene 126,000 �� 5,000 years ago. willbe offset from the model's predictions by 10-15% of absolute age.Accurately calibrated radiocarbon dates are essential in correlatingradiocarbon-dated phenomena with Milankovitch models, cyclothems, andwith direct radiometric methods such as TL or U/ Th disequilibrium disequilibrium/dis��equi��lib��ri��um/ (dis-e?kwi-lib��re-um) dysequilibrium.linkage disequilibrium dating, which can be used to link culture to climate. Since thebeginnings of farming in western Asia occur just around thePleistocene/Holocene boundary, these considerations apply withparticular force.(5) Next, precision. A more or less continuous fine-grained fossilatmospheric record has been obtained from Greenland ice-cores (Dansgaardet al. 1993), which conveniently shows annual deposition and so allowsindependent dating in `ice-core years' (which in principle shouldcorrespond to dendro-calibrated [sup.14.C] years). It is thus possibleto measure closely-dated isotopic and other chemical variations, andalso ice-accumulation rates, reflecting different aspects of globalclimatic changes (Johnsen et al. 1992; Alley et al. 1993; Peel 1995;Lowe & Walker 1997). In addition to the broad record of climaticchange, the detail of the ice-core record has also revealed short-termperiodicities which may be `overtones' of the Milankovitch cycles(Kerr 1996). These high-frequency changes, often of some magnitude,would have occurred very suddenly and may have been important instressing populations (including early humans) in marginal or ecotonalsituations (van Andel & Tsedakis 1996).(6) The latest and sharpestof these fluctuations was the Allerod/Younger Dryas cycle. Ice-coreshave thus provided a crucial combination of accuracy and precision indefining climatic changes. The pattern of continuous variation revealedin the ice-cores indicates that classic palynological entities like theDanish Bolling and Allerod warm phases are less like discrete,continuously warm intervals than segments of a rapidly changingtemperature curve. Global changes would also have had different localexpressions, depending on specific thresholds of climatic and biologicalchange. The direct evidence of local vegetational conditions provided bypollen analysis Analysis of the distribution of pollen grains of various species contained in surface layer deposits, especially peat bogs and lake sediments, from which a record of past climate may be inferred. of lake-sediments and peats is thus often difficult tocorrelate, and requires radiocarbon dates that are not always availablefor some critical sequences (especially in southwest Asia Southwest Asia or Southwestern Asia (largely overlapping with the Middle East) is the southwestern portion of Asia. The term Western Asia is sometimes used in writings about the archeology and the late prehistory of the region, and in the United States subregion : Hillman1996); though it is possible to circumvent this problem by tuning longterrestrial pollen sequences to isotopically-characterized pollen phasesin nearby marine sediments (Rossignol-Strick 1993; 1995; Tsedakis 1994;cf. Bottema 1996).(7) Although not yet fully integrated, these threeelements -- the Milankovitch model, the isotopically-derivedtemperature-curves from remote but continuously accumulating sedimentaryenvironments, and the more sporadic snapshots of local vegetationalevidence -- are beginning to come together into a coherent picture(Aitken et al. 1993; Wright et al. 1994; Lowe & Walker 1997). Out of all these complications comes the following conclusion: thePleistocene climate was even more unstable than was once supposed, andthe end of the last glaciation was not a simple shift from glacial tointerglacial in��ter��gla��cial?adj.Occurring between glacial epochs.n.A comparatively short period of warmth during an overall period of glaciation. modes some 10,000 years ago but a period of very pronouncedinstability in which temperatures oscillated with a speed and amplitudefar greater than anything experienced in the Holocene (Figure 1). (Theend of the Younger Dryas, for instance, saw an astonishing rise in meanJuly temperature of 7 [degrees] C in just 50 years: Lowe et al. 1995).It was a de-stabilizing experience, characterized both by uncertaintyand by sudden reversals of prevailing average conditions on a timescaleof millennia or centuries. The Younger Dryas has now been recognizedworld-wide as a sudden reversion to glacial conditions following agenerally milder phase of the Late Glacial (Troelstra et al. 1995).After a `false dawn' of warmer conditions, the world was plungedonce more into relative dryness and cold. This instability, likely tohave been an important factor in the local (and, in some cases, total)extinction of members of the megafauna meg��a��fau��na?n. (used with a sing. or pl. verb)Large or relatively large animals, as of a particular region or period, considered as a group.meg in parts of the northernhemisphere, both in Eurasia and the Americas (Grayson 1991), has alsobeen invoked as a critical factor in the beginning of farming in westernAsia (Moore & Hillman 1992). As a globally recognizable signal, itis being used to explain why farming might have appeared simultaneouslyin different parts of the world (e.g. Cavalli-Sforza 1996: 51).Explanations in terms of population pressure (Cohen cohenor kohen(Hebrew: “priest”) Jewish priest descended from Zadok (a descendant of Aaron), priest at the First Temple of Jerusalem. The biblical priesthood was hereditary and male. 1977) or increasingfamiliarity with the environment (Braidwood 1962), it is argued, couldnot give rise to such simultaneity. This gives a fresh lease of life toclimatically-driven models of agricultural origins, in the tradition ofChilde's famous desiccation des��ic��ca��tionn.The process of being desiccated.desic��ca or `oasis' hypothesis (1956: 76-7;Cf. Wright 1993; Blumler 1996: 41). [FIGURE 1 ILLUSTRATION OMITTED] Defining terms and identifying thresholdsThis renewed climatic emphasis is an important part of currentexplanations of the beginning of farming in western Asia (Bar-Yosef& Belfer-Cohen 1989; 1991; Bar-Yosef & Meadow 1995), which beganwith Flannery's classic formulation of 1965, emphasizing theremoval of plants and animals (in the same way as obsidian and bitumen bitumen(bĭty`mən)a generic term referring to flammable, brown or black mixtures of tarlike hydrocarbons, derived naturally or by distillation from petroleum. )from their natural habitats, thus subjecting them to new forms ofselection. In particular, as Zohary explained (1969), the deliberatesowing of cereals would lead to selection for non-shattering forms --though only, as Kislev emphasized (1984), if they were sown away fromself-seeding wild stands. Harvesting methods were important in thisselection process: especially use of the sickle, rather thanbag-and-stick method (Wilke et al. 1972). This cutting technology wasprobably developed for basketry basketry,art of weaving or coiling and sewing flexible materials to form vessels or other commodities. The materials used include twigs, roots, strips of hide, splints, osier willows, bamboo splits, cane or rattan, raffia, grasses, straw, and crepe paper. (which required the harvesting oflong-stemmed monocotyledons MonocotyledonsThis group of flowering plants (angiosperms), with one seed leaf, was previously thought to be one of the two major categories of flowering plants (the other group is dicotyledons). ), and use of baskets was itself a crucialelement in the technology of gathering small seeds.(8) Cereals, alongwith other elements of the Mediterranean vegetation such as nut-bearingtrees, became more common in southwest Asia with the ending of steppe steppe(stĕp), temperate grassland of Eurasia, consisting of level, generally treeless plains. It extends over the lower regions of the Danube and in a broad belt over S and SE European and Central Asian Russia, stretching E to the Altai and S to conditions which prevailed during the glaciation (Wright 1977; Street1980). Cereals were probably not the most attractive of the newresources, since they require labour-intensive processing (Wright 1994);and they probably formed only a small component of the intensifiedcollecting strategies of `Epipalaeolithic' groups after 14,000 BC(16,000 BP), when human populations expanded spatially and in someplaces became more sedentary. The cyclical downturn in climate after11,000 BC (13,000 BP) at the beginning of the Younger Dryas, by creatinga bust after the earlier boom, could well have been locally critical innecessitating reliance on initially less attractive and time-consumingresources such as the cereals (Henry 1989): literally `grindingpoverty'.(9) At the same time, it critically altered lowlandhabitats by reducing the area of lakes within the Jordan rift (Yechieliet al. 1993; Goldberg 1995:45; Goldberg & Bar-Yosef in press). The use of a climatic trigger as an explanation in other parts ofthe world does, however, raise the crucial definitional problem of whatprecisely is meant by the `beginning of farming; for while the climaticsequence has been defined with increasing precision, archaeologists maymean quite different things when they talk of `farming'.Archaeological concepts typically evolve in the following sequence:first, an accepted stereotype is opposed to another, in classicstructuralist fashion (`farming' vs `hunting'); then thechange is equated with the appearance of some archaeological phenomenonin a particular area (polished stone axes, or pottery); then the ratherdifferent archaeological records of several areas are compared, and adefinitional fudge emerges, which covers up the conceptual confusion.There is then a free-for-all, in which new recognition-criteria (e.g.biological ones) are proposed, the concept itself is attacked ontheoretical (and sometimes political) grounds, and various academiccommunities use the same term in completely different ways, sometimesintroducing fresh confusion by mis-reading each others' literature.Thus the term `Neolithic' may be used of hunters using polishedstone axes or of village-dwelling cultivators, and `farmers' ofcave-dwellers collecting plants which may (or may not) have beengenetically altered by selective gathering. The conceptual links betweenthese various cases are of different kinds: both historical (in terms ofthe spread of a particular crop-complex) and analogical an��a��log��i��cal?adj.Of, expressing, composed of, or based on an analogy: the analogical use of a metaphor.an (in the case ofdifferent `Neolithics'). The term has been extended bothmetonymically me��ton��y��my?n. pl. me��ton��y��miesA figure of speech in which one word or phrase is substituted for another with which it is closely associated, as in the use of Washington for the United States government or of and metaphorically from its paradigm. It makes thequestion of defining a starting-point, to see if it equates with theonset of a particular environmental change, especially problematic. More than problematic: practically self-fulfilling for those whoseek climatic correlations. Like the tautologous Tau`tol´o`gousa. 1. Repeating the same thing in different words; tautological. procedures of eastMediterranean archaeologists in the later prehistoric periods, who inthe absence of fine chronological control align destruction-levels ondifferent sites into hypothetical `horizons' (often equated withhistorical events and personalities), the inherent imprecision ofdefinition can create apparent equations between archaeological andenvironmental changes. The equations seem convincing because of anunconscious Procrustean truncation which lops off those parts of thephenomenon that do not fit. Thus the microlith-using and cereal-eatingNatufian culture The Natufian culture existed in the Mediterranean region of the Levant. It was an Epipalaeolithic culture, but unusual in that it established permanent settlements even before the introduction of agriculture. of Palestine, initially considered `Mesolithic' bynorth European prehistorians like Kathleen Kenyon Dame Kathleen Mary Kenyon (5 January, 1906 – 24 August, 1978), important English archaeologist of Neolithic culture in the Fertile Crescent and excavator of a small area of Jericho in Israel from 1952 to 1958. , is now dated to theclosing centuries of the Pleistocene and so becomes Palaeolithic (or,worse, `Epipalaeolithic', like an irrelevant afterthought). Thisterminology, itself quite arbitrary, subconsciously reinforces theconception that such groups could only have been gathering'cereals. Since morphological criteria of `domestication' -- thespecialist botanical usage implying that humanly-caused genetic changeshave taken place, deleterious to the plant in the wild -- are notevident before the Holocene, the diagnosis appears confirmed.Pleistocene = wild = foraging: Holocene = domestic = farming -- theequations have a Levi-Straussian symmetry. On the other side of the world, things are rather different. InMesoamerica and Andean South America South America,fourth largest continent (1991 est. pop. 299,150,000), c.6,880,000 sq mi (17,819,000 sq km), the southern of the two continents of the Western Hemisphere. , the two nuclear areas of thecentral American Central AmericaA region of southern North America extending from the southern border of Mexico to the northern border of Colombia. It separates the Caribbean Sea from the Pacific Ocean and is linked to South America by the Isthmus of Panama. nuclear region, there are up to now no Pleistoceneprecedents. According to according toprep.1. As stated or indicated by; on the authority of: according to historians.2. In keeping with: according to instructions.3. one view (which I do not share), this isbecause human populations had only recently arrived on the continent;according to another, extinction of the megafauna caused humanpopulations to shift their sights lower down the trophic trophic/tro��phic/ (tro��fik) (trof��ik) pertaining to nutrition. troph��icadj.Of, relating to, or characterized by nutrition. pyramid.Preservation bias, and less intensive investigation than in the case ofwestern Asia, must also play a part in obscuring the picture. Moreoverthese tropical hearths have a greater range of plants known at a laterdate to have been cultivated: gourds and fibre-plants, peppers androot-crops, as well as the cereal, maize. Maize is itself a problem,since the question of its ancestry is not entirely settled: whether itis the still-living teosinte teosinte:see corn, in botany. teosinteTall, stout, annual grass (Zea mexicana or Euchlaena mexicana) of the family Poaceae (or Gramineae), native to Mexico. , or a now extinct wild maize (Bird apudBlumler & Byrne 1991: 36-7). On the former model, the occurrence ofany maize-plant, however primitive, tends to be accepted as evidence fordomestication domesticationProcess of hereditary reorganization of wild animals and plants into forms more accommodating to the interests of people. In its strictest sense, it refers to the initial stage of human mastery of wild animals and plants. , hence for cultivation, even for agriculture.(10) Forplants which did not undergo major genetic changes, even greater freedomof interpretation is possible: their very occurrence in archaeologicaldeposits, or even in pollen-profiles, is often equated withdomestication. These procedures push dates backwards, nearer and nearerto the beginning of the Holocene -- the reverse of the western Asiatictendency. Commonly quoted dates are, for instance, 7000-5000 BC forplants such as avocado, chilli peppers, beans, squash, maize and manioc manioc:see cassava. (e.g. Scarre 1988: 208-9). Yet while certain high-value spice-plants mayhave an older history, the most striking aspect of this sequence to theOld World prehistorian is the late appearance of cereal-cultivation onsufficient a scale to influence settlement-patterns. Whereas in westernAsia the shift to a village-based pattern did indeed coincide with theother changes summarized above, in Mexico the shift from caves tovillages only took place after 3000 or even 2000 BC, when maize becamethe crucial crop. It is only the conjunction of these two tendencies -- to down-datethe appearance of `farming' in the Old World, but to up-date it inthe New -- which gives a superficial impression of their being roughlycontemporary.(11) Comparable phenomena in the two hemispheres are infact some 6000 years apart, just as 4000 years separated the firstappearance of urbanism in the two areas. It is evident that the OldWorld and the New World marched to different rhythms. By aligning thesequences correctly, it is possible to dispose of To determine the fate of; to exercise the power of control over; to fix the condition, application, employment, etc. of; to direct or assign for a use.See also: Dispose the oft-repeatedgeneralization that in the Old World, sedentism preceded farming, but inthe New World farming preceded sedentism. This crucially depends on whatis meant by sedentism, and by farming; and it would be truer to say thatcereal-use and sedentism marched closely in step. Natufian sites, in thelast two millennia of the Late Glacial (and associated with thelarge-scale use of plants including cereals), do show some evidence ofsemi-permanent habitation HABITATION, civil law. It was the right of a person to live in the house of another without prejudice to the property. 2. It differed from a usufruct in this, that the usufructuary might have applied the house to any purpose, as, a store or manufactory; whereas structures -- circular hut-bases (withsparrows and housemice), on terraces outside caves or on the openplateau -- and Natufian levels underlie some important Neolithic sites(Jericho, Mureybit, Tell Abu Hureyra Tell Abu Hureyra ("tell" is Arabic for "mount") was a site of an ancient settlement in the northern Levant or western Mesopotamia. It has been cited as showing the earliest known evidence of agriculture anywhere. ); but this is clearly differentfrom the permanent sedentism of the succeeding Neolithic, with itstell-based settlements in low-land settings (Henry 1989; Byrd 1989;Bar-Yosef & Valla 1991). A very similar sequence can be inferred forwell-investigated parts of Mexico like Oaxaca and the Tehuacan valley:the inhabitants of long-occupied caves made some use of maize longbefore their village-dwelling successors used more intensive techniquesof farming in the valley-bottoms. The parallelism seems quite precise,despite the different seasonality of the crops involved, and the factthat villages in the Americas first appeared halfway through theHolocene whereas in Eurasia they had existed since its beginning. Inboth cases, the crucial shift was a move from upland to lowland, andfrom caves or campsites to villages, unlocking the productive potentialof alluvial habitats and effectively opening up fundamentally new nichesfor the human species (Sherratt 1980). Rather than basing terminology on human behavioural patterns onlyindirectly reflected through genetic changes in plants, it seems betterto use this major residential change, directly manifested in thearchaeological evidence, as the crucial point of transition marking whatGordon Childe justifiably called the Neolithic Revolution.(12) Theemergence of a village community and its households, directly supportedby farming, can be unambiguously identified; and it was pregnant withsocial, cultural, economic and demographic consequences: as a`privatization' of resources it marked the ending of the foragersharing ethic (Boyd 1994; cf. Flannery 1972), and as a commitment to amore permanent corporation it created new roles both for the living andfor the dead (Cauvin 1994). This insight has been rather lost in theproliferation of biological expertise which has accompanied the growthof archaeological science Archaeological science (also known as Archaeometry) is the application of scientific techniques and methodologies to archaeology.Archaeological science can be divided into the following areas: ; and it is important to re-assert the primacyof a social definition. Anthropologists are introduced to thefundamentals of kinship through the Latin tag pater PATER. Father. A term used in making genealogical tables. est quem nuptiaedemonstrant: the legal father (who is not necessarily the genitor gen��i��tor?n.1. One who produces or creates.2. Anthropology A natural father or mother.[Middle English genitour, from Old French genitor ) isthe person indicated by the marriage ceremonies; the social takesprecedence over the biological. The farmer, on the same principle, canbest be defined by his/her way of life and habit of dwelling inhouses:(13) agricola est quem domus demonstrat. The principle is of verywide extension: Stephen Shennan (1993) has recently advisedarchaeologists to deal directly with the cultural phenomena to whichthey have immediate access, rather than with indirectly inferred socialstructures, which must always remain hypothetical; in much the samespirit as Claudio Vita-Finzi (1969) once encouraged environmentalists totalk directly about changes in soils or vegetation, rather thantranslating their evidence into a speculative climatic koine-. In acomparable context, Norman Yoffee has propounded the rule (1993: 69),that `if you can argue whether a society is a state or isn't, thenit isn't': a concrete demonstration is more useful than ahypothetical equation. Few prehistoric phenomena are more concrete thana tell; it makes sense to see the appearance of such substantialhabitation residues as the critical indicator of a sustained commitmentto farming.(14) From `proto-horticulture' to farming: a punctuated changeThis definition permits a more realistic comparison of the Old andNew World sequences, and a recognition of their systadial (to use afavourite word of Gordon Childe)(15) characteristics. The shift to avillage-based pattern in Formative Mexico was preceded by three or fourthousand years of experience of what were to become major crop plants,by various methods of manipulation. So too, probably, was the beginningof tell-formation in Neolithic Palestine: the preceding period ofexperimentation would thus be equivalent to the Natufian. Being stillPleistocene (even if Late-Glacial), the Natufians commonly appear intextbooks as passive collectors of nature's gifts (even thoughMesolithic communities in temperate Europe are increasingly beingportrayed as active ecological agents, especially by the use of fire).Yet Natufians can also be seen in the same light as the pre-Purron phaseinhabitants of the Tehuacan valley: semi-mobile groups engaging incollecting and some seed-planting, in a way once described as `barranca bar��ran��ca? also bar��ran��con. pl. bar��ran��cas also bar��ran��cos Southwestern U.S.1. A deep ravine or gorge.2. A bluff. horticulture' -- the propagation of individual hardy cultivars instream-gullies near the cave sites. If these Archaic Americans were`farmers', then so in all probability were some Natufians --especially the Late Natufians of the central Levantine Le��vant?1?The countries bordering on the eastern Mediterranean Sea from Turkey to Egypt.Le Corridor(Bar-Yosef & Valla 1991; cf. Hillman et al. 1989; Hillman 1996).Whatever the precise mode of exploitation (and whether at this stage ithad a perceptible selective effect), there seems no point in placingthem in different categories. The same considerations apply to otherearly `farmers' without villages, perhaps even the inhabitants ofKuk swamp (Golson 1989): there is no reason to suppose that the degreeof habitat modification reflected in drainage ditches dated to varioustimes in the early and middle Holocene were different in principle fromthose employed by the Late Glacial inhabitants of the Levant Levant(ləvănt`)[Ital.,=east], collective name for the countries of the eastern shore of the Mediterranean from Egypt to, and including, Turkey. . All ofthese can be seen as a sort of proto-horticulture, which only in certaincases led on to full farming. What these examples have in common is the propagation on a smallscale of productive, starch-storing species (mostly of annual habit) inareas which stabilize and extend their productivity by more abundantsoil moisture. These were perhaps initially small topographic featuresor soil patches, close to the wild stands of plants which made animportant contribution to diet, where minimal habitat alteration wasrequired beyond a little help in implantation and avoiding competition.(In the Levant, vertisols may have been important at this stage: Limbrey1990.) This would not, however, greatly alter the selective pressuresfrom those affecting a wild population. The more radical alternativewould be to move such plants from their area of natural occurrence tomore distant (but inherently more productive) alluvial habitats wheremore concentrated cultivation could take place -- usually requiringpermanent residence, and thus the creation of houses. In the lowerJordan valley, this was facilitated by climatic change: the Lisan Lake,which at its maximum in the Geometric Kebaran had covered much of theJordan rift below -200 m, had fallen rapidly during the Younger Dryas toexpose the surfaces upon which alluvial fans could develop, and so makepossible this expansion of lowland cultivation (cf. Vita-Finzi 1969;Sherratt 1972). Upland pressure was balanced by lowland opportunity; thedemographic shift to the alluvium al��lu��vi��um?n. pl. al��lu��vi��ums or al��lu��vi��aSediment deposited by flowing water, as in a riverbed, flood plain, or delta. Also called alluvion. was the decisive locational move. Thenewly chosen sites were often nodal points on routes of inter-regionalcontact (themselves closely related to valleys and water-sources), wherepopulations wished to concentrate for social reasons and the exchange ofgoods. The locations of Jericho (by a major spring in the Jordan valley)and Tell Aswad (by a lake-edge near Damascus) well exemplify theseproperties, in what were probably the two focal areas of the process(Dorrell 1978; van Zeist & Bakker-Heeres 1982: 239-40). The shift from largely self-seeding to artificially sownpopulations would have minimized losses to predators,(16) and at thesame time intensified selective pressures leading to non-shatteringforms and loss of seed dormancy (Zohary 1996). Protecting the seed-grainover winter would also reduce the pressure for tough, protecting glumes,ultimately allowing the emergence of naked forms. The move from apattern of growth sustained by winter rainfall to one using highsoil-moisture in spring may also have involved a specific adaptation toa pattern of spring rather than winter growth (Sherratt 1980).(17)Although not identifiable morphologically from ancient material untilthe anatomical changes had become apparent, the emergence of a stronglowland-adapted variety (perhaps initially at only one or two sites)would have superseded less intensively husbanded varieties and madecereal-based farming viable. This kind of transfer may have beenattempted repeatedly, perhaps initially with limited success,(18) beforecontinued selection led to the evolution of varieties adapted to newedaphic e��daph��ic?adj.1. Of or relating to soil, especially as it affects living organisms.2. Influenced by the soil rather than by the climate. conditions and seasonal growth-patterns: but it was these thatmade possible the beginning of village life.(19) Farming thus began,metaphorically, with a distinct `click': it was an event-likephenomenon. Although this major locational and demographic shift wasessentially a scaling-up of existing practices, rather than theappearance of completely new forms of behaviour, it nevertheless led toemergent properties not manifested with previous levels of activity. Thedemographically explosive potential of farming now began to becomeapparent, accompanied by a marked increase in the pace of culturalchange, as populations became `locked in' to cereal cultivationwith its reciprocating cycle of population growth and agriculturalintensification (despite new diseases and parasites). The consequencewas an increasing scale of interference with natural ecosystems,diverting an increasing proportion of their productivity to humansubsistence. This model integrates many of the ideas persistently proposed toexplain early farming. It does not preclude the small-scale cultivationof particularly useful plants (and even exotic species, obtained bylong-distance exchange) as part of a semi-nomadic existence, beforeobligate reliance on carbohydrate crops.(20) Centres of futureintensification probably played a role within pre-existing networks ofexchange. Natufians may well have been cultivating flax, for instance atJericho, even if they were only harvesting largely wild cereals on theJudaean hills; other horticultural plants, potentially grown before themajor transition to lowland habitats and the bulk cultivation ofcereals, could have included drugs (such as Hyoscyamus, a typical`dumpheap' semi-domesticate, known to have been consumed rituallyin later Neolithic Scotland), spices like coriander coriander(kōr'ēăn`dər), strong-smelling Old World annual herb (Coriandrum sativum) of the family Umbelliferae (parsley family), cultivated for its fruits. ,(21) and fibre- oroil-producing plants. Such species may well have been traded, dead oralive, from one area to another over similar distances to shells likeDentalium, From Peru at a comparable stage there is evidence of thetransfer of high-value plants from adjacent phytoclimatic zones, andtheir propagation in small numbers to provide containers, fibres, spicesand variety plants. Cotton, gourds and peppers were cultivated in thelowlands when the bulk foods were of maritime rather than agrarianorigin; later on, plants producing the materials for hallucinogenic hal��lu��ci��no��gen?n.A substance that induces hallucination.[hallucin(ation) + -gen.]hal��lu snuffs were valuable items of trade (cf. Torres et al. 1991). Such amodel would conform to the very general pattern of high-value productionpreceding bulk production -- from luxuries to commodities (Sherratt& Sherratt 1991). Like the circulation of prestige-goods before theonset of urbanization, the tending (and perhaps exchange) of usefulplants was a precondition for the initiation of farming. Climatic triggers and climatic controlsWhat, then, was the relation between the beginning of farming andpatterns of climatic change? Temporary climatic deterioration may wellhave forced populations to cultivate artificially the calorie-providingspecies normally collected from the wild, at places where theirproduction could be expanded. When conditions ameliorated, the way oflife so created was able to expand. It was the cyclical nature of theprocess (carrot/stick/carrot) which provided the stimulus. Such smallcycles were set within the larger Milankovitch cycles of glaciation anddeglaciation de��gla��ci��a��tion?n.The uncovering of glaciated land because of melting or sublimation of the glacier.deglaciation?The uncovering of land that was previously covered by a glacier. . The onset of interglacial conditions (with their enhancedseasonal contrasts) after the prevailing cold and dryness of the lastglaciation was an enabling, possibilistic development: although in someareas it reduced opportunities for hunting large game animals (throughafforestation and local extinction), in others it opened up a much widerrange of plant-collecting opportunities -- especially the high-yieldingspecies adapted to seasonal stress by food-storage. Mediterraneanclimate and its corresponding vegetation had largely disappeared underglacial conditions, its constituent species surviving only in refugeslike parts of the Jordan rift (Byrne 1987; Blumler & Byrne 1991;McCorriston & Hole 1991).(22) A flush of such species became morewidely available in the southern Levant, beginning as early as 15,000 BC(17,000 BP), at the onset of the Late Glacial: notably in the eastMediterranean where rainfall became more abundant,(23) and one mayenvisage both intensified collecting and habitat-enhancement forcarbohydrate crops as well as a (more speculative) development ofhigh-value crops that were perhaps traded, both as viable seeds andplant-products, between adjacent areas -- on the scale, say, of obsidianor exotic shells. The Natufian, in this sense, is `Mesolithic', inthat it reflects the early peak of productivity with the onset ofinterglacial conditions (like the `hazel boom' which sustained theearlier Mesolithic in temperate European forests, 5000 years later: theeffects of warming were felt earlier in the south). This trend wasreversed, however, by the Younger Dryas, 11,000-9,500 BC (13,000-11,500BP), with an abruptness which precluded smooth homeorhetic adjustment;this large-scale oscillation de-stabilized the new balance, but wouldhave required an increasingly interventionist attitude in the face ofsuddenly declining returns from gathering wild cereals (Henry 1989). Forsocieties grown dependent on the new opportunities, the environmentalabout-turn helped to precipitate a commitment to the more dependableconditions of better-watered lowland alluvial soils: and the Pre-potteryNeolithic A tell of Jericho (and its nearby contemporaries Gilgal I,Salibiya IX and Netiv Hagdud) was the consequent result. The alternativewould have been intensified acorn-gathering or gazelle-hunting -- bothof which were probably adopted in less favoured areas of the forest beltand steppe respectively (Wright 1994; McCorriston 1994; Garrard et al.1996). This instability triggered the shift to wheat-farming in westernAsia, and a comparable decrease in monsoonal rainfall may have hadsimilar effects in initiating rice-farming in eastern Asia as well(Glover & Higham 1996; Bellwood 1996): here too, the bufferingqualities of water-retentive soils would have been important in a phaseof dryer climate, and initial forms of horticulture were centred inalluvial habitats. This particular climatic wobble wobble/wob��ble/ (wob��'l) to move unsteadily or unsurely back and forth or from side to side. See under hypothesis. wob��blen.1. was in no wayessential, however, since a precisely similar sequence of events tookplace on the other side of the world some 6000 years later: nouniformitarian equation is required. The Younger Dryas was thus aproximate cause An act from which an injury results as a natural, direct, uninterrupted consequence and without which the injury would not have occurred.Proximate cause is the primary cause of an injury. of the onset of farming for one (or both) of the OldWorld centres; and it remains to be seen whether there was anycomparable climatic trigger to the onset of maize-farming -- such as aprecession-driven mid-Holocene dry phase with reduced monsoonalrainfall, parallel to Saharan desiccation -- in Mesoamerica. This description emphasizes the stored-up potential for changewhich was released by the onset of interglacial conditions. A propensityto interfere with the environment in unexpected ways seems to have beenan inherent characteristic of modern humans: in this perspective, the`origins of farming' have as much to do with the appearance oflanguage and symbolic systems as they have to do with climatic change.The coincidence between the appearance of farming and the onset ofHolocene conditions was thus more a matter of opportunity than ofmotivation: behaviourally modern people like to mess around withplants,(24) and would have done so during the glacial if there had beenmore useful ones around. In the tropics tropics,also called tropical zone or torrid zone, all the land and water of the earth situated between the Tropic of Cancer at lat. 23 1-2°N and the Tropic of Capricorn at lat. 23 1-2°S. , where candidates were moreplentiful, there is increasing evidence of manipulation and deliberateintroductions before 15,000 years ago (Spriggs 1996: 533). It is thus nosurprise that archaeobotanists can identify manipulation wherever theyare provided with samples -- but this is not necessarily farming, onlyits preconditions.(25) Large-scale cultivation which deserves to becalled `farming' was a rather rare development, which came aboutindependently perhaps in only three regions of the world -- the nuclearregions of western Asia, eastern Asia and the central Americas. Allthree were cereal-based, and concerned species which flourishedprincipally during interglacials. The kinds of mutual interdependencebetween humans and cereals (which led to runaway population growth inboth sets of organisms, and their parasites) were only probable underinterglacial conditions: and they appeared at the first opportunityafter the emergence of modern behavioural complexity. The beginnings offarming, in the forms which became widespread, were both punctuate punc��tu��ate?v. punc��tu��at��ed, punc��tu��at��ing, punc��tu��atesv.tr.1. To provide (a text) with punctuation marks.2. andexplosive (Figure 2), replacing more slowly-evolving mutualisms.Individual plants and animals were added in other places, but theprimary complexes expanded so fast through the Old World that otherfully independent centres had no time to develop. The centres ofindependent farming in the New World were only able to make so belatedan appearance because of their isolation from the rest of the world,which protected them from the spread of foreign crops and allowedindigenous domesticates to be developed. The widespread appearance ofagriculture in the early Holocene is thus due, not to a unique set ofspecific conditions which never recurred, but to its enhancedprobability of occurrence in a few critical areas, and a pattern ofexplosive expansion once it had appeared: farming, once discovered,permitted no return. [FIGURE 2 ILLUSTRATION OMITTED] The oasis hypothesis and the Upper PalaeolithicClimatic reversions like the Allerod/Younger Dryas oscillation arethus an important component of the explanation of agricultural origins.Such cycles, tempting human populations to expand and then lowering theceiling, were typical of the Pleistocene. The largest example of sucheffects is the changing Sahara desert, successively sucking in humanoccupants and then expelling them -- what I have called the `Saharanpump' (Roberts 1984), which was an important factor in propellingsuccessive hominid hominidAny member of the zoological family Hominidae (order Primates), which consists of the great apes (orangutans, gorillas, chimpanzees, and bonobos) as well as human beings. populations out of Africa. This makes the oasis modelrelevant to that other potentially punctuate phenomenon, the HumanRevolution. just as the Younger Dryas is being used by climatologists asa well-documented example of a more frequent phenomenon, so models ofthe beginning of farming may help to illuminate earlier episodes ofchange. Was it, perhaps, as a result of adjustment to desiccation thatthe final elements of the Human Revolution clicked into place? Despite his perspicacity, Childe's original conception of theorigins of farming was nevertheless based on a fundamentalmisunderstanding; for he relied on C.E.P Brooks' climaticreconstruction, which assumed that high-latitude `glacials'corresponded to southern `pluvials', because of the southwarddisplacement of the westerly depression-tracks by high pressure over theice (Childe 1954: 15; Brooks 1924). We now know that the reverse is thecase:(26) the properties of global atmospheric circulation duringglacials made them both cold and dry (in the tropics as much as inotherwise temperate latitudes),(27) while the earlier part of theHolocene saw not only an increase in westerly (cyclonic) rainfall butalso a strengthening of monsoonal circulation and increased summer(convectional) rainfall in the Sahara and Indian Ocean. Childe'svision of a generally desiccated world thus applies, not to thebeginning of the postglacial post��gla��cial?adj.Relating to or occurring during the time following a glacial period.postglacial?Relating to or occurring during the time following a glacial period.Adj. 1. , but to the preceding glacial period ingeneral -- within which there were further contrasts between relativelywetter or dryer phases (Goodfriend & Magaritz 1988). Whereas at theonset of a glaciation human populations north of the Mediterranean wouldhave been subjected to extremes of cold, those south of it (in theLevant and north Africa) would have been both increasingly cut off fromother African populations by the expanding Sahara, and also faced withcompetition from groups driven south by cold. At the same time thesepopulations would themselves have been subjected to periodic extremes ofdrought, and the consequent need to sustain networks of contact -- ifonly for demographic reasons -- between individual oases of population(cf. Clark 1993). Is it coincidence, therefore, that the UpperPalaeolithic -- which like the Neolithic marks a threshold of decisivebehavioural change in the archaeological record - seems to have had itsfirst manifestation where these processes would have been most intense:in the Levant? Recent discussion of the Human Revolution has tended to directattention southwards, in an `out of Africa' scenario for theappearance of modern human populations -- Anatomically Modern Humans, orAMH AMH Abington Memorial Hospital (Abington, PA)AMH Anti-M��llerian HormoneAMH Australian Medicines HandbookAMH Automated Material HandlingAMH Aviation Structural Mechanic (Hydraulics)US Navy Rating (Nitecki & Nitecki 1994); though in effect, of course, we aretaking about skeletally modern humans, since the bones are all thatsurvives. Such anatomically modern populations existed in Africa and theLevant by 100,000 years ago -- both in the far south (Border Cave andKlasies River) and northwards as far as the Carmel caves (Skhu-l andQafzeh). Their contemporaries the Neanderthalers, by contrast, wereevolving in a different direction, physically adapting to the extremeconditions on the cold northern edge of human existence. AMH populationsevolved at much the same time as Neanderthal ones, and ultimatelyreplaced them (Schwarcz 1994; Klein 1995). The two groups initiallyshared a common material culture, the Middle Palaeolithic/Middle StoneAge tool-kit; and during the earlier part of the last glaciation,Neanderthals expanded southwards, into the Levant. After 50,000 yearsago, however, AMH groups in the southern Levant and northeast Africadeveloped an Upper Palaeolithic tool-kit (Gilead 1991; Bar-Yosef 1993;Phillips 1994), and thereafter slowly replaced Neanderthals in Europe,from east to west. Late Stone Age tool-kits, with these advancedfeatures, appeared in Africa over a similar timescale (45-25,000 yearsago). The broad pattern thus suggests divergence between thosepopulations in the harsh northern margins of the human distribution, whoadjusted to increasingly cold conditions by physical adaptation (`woollyhumans', like woolly mammoth),(28) and those more centrally-placedpopulations who did not undergo these specializations, but whosecultural development ultimately gave them the advantage. The criticaltransformation arguably took place, therefore, in southwest Asia andadjacent parts of northeast Africa -- from which innovations spread backinto sub-Saharan Africa, over the same timescale as they spread toEurope (though perhaps without the same degree of populationreplacement). While it may be strictly true that Anatomically ModernHumans are oldest in Africa, this statement to some extent simplyreflects the limited inferences which can be made from skeletal anatomy;what may be more important is that Behaviourally Modern Humans (Gamble1995:157) -- whom we might designate with an analogous acronym as BMH BMH Blount Memorial HospitalBMH Base Message HostBMH British Motor Holdings --may well have emerged in more or less the same region as the one whichwas subsequently to be the earliest nuclear area of agriculture. Modernhuman culture, and its implied behavioural, organizational and evencognitive changes (probably including fully modem linguistic competence)seem on the basis of these archaeological indications to have made theirappearance there (Marks 1983; 1990). If the hardware was African, thesoftware appears to have been Levantine, with the new pattern configuredat the complex junction of Africa and Asia. Biology, culture and climateFrom this perspective, the changes which brought about the beginningof farming were a continuation of those that had given rise tosuccessive generations of African hominids. Increasing aridity,cyclically intensified, is the process that has periodically driven muchof mammalian (including human) evolution in the later Cenozoic,particularly in East Africa (Vrba et al. 1996). Moreover this has beenparticularly significant in the varied landscapes of the rift systemwith its rivers and fluctuating playa lakes, which provided both varietyand the conditions of reproductive isolation conducive to speciation speciationFormation of new and distinct species, whereby a single evolutionary line splits into two or more genetically independent ones. One of the fundamental processes of evolution, speciation may occur in many ways. .The corridor linking the Ethiopian highlands to southern Africa was thecradle of the australopithecine aus��tra��lo��pith��e��cine?n.Any of several extinct humanlike primates of the genus Australopithecus, known chiefly from Pleistocene fossil remains found in southern and eastern Africa.adj. and earliest hominine lineages. With thedispersal of Homo erectus, the hominid distribution extended to otherparts of Africa and beyond, but the rift system seems to have remained acore area of evolutionary development -- whose turnover pulses were nowforced by an increasing scale of environmental alternation alternation/al��ter��na��tion/ (awl?ter-na��shun) the regular succession of two opposing or different events in turn.alternation of generations? metagenesis. correspondingto high-latitude glaciation and deglaciation -- from which successivegenerations of dry-selected hominids (and other mammalian species)dispersed into Eurasia, on the model of centrifugal speciation. As the area occupied by hominids extended beyond Africa, the focusof potential genetic (and cultural) diversity moved northwards. The riftsystem nevertheless remained an important axis, since the principalgateway to other continents lay along the Nile or Red Sea and throughthe Levant. Although strongly stressed in dry pleniglacial conditions,this corridor occupied a pivotal point in the centre of the hominiddistribution, and saw an early appearance of AMH. By the laterPleistocene, however, a separate, `cold-selected' genotype wasemerging (initially in partial isolation?) on the margin of the humandistribution north of the Mediterranean: the Neanderthals. This lineageincreasingly traded off all-round ability against specific adaptivefitness to glacial conditions. The Levant was thus in the tension zonebetween two differentiating human lineages, and since hybridization hybridization/hy��brid��iza��tion/ (hi?brid-i-za��shun)1. crossbreeding; the act or process of producing hybrids.2. molecular hybridization3. between them would not have increased adaptive fitness, it is likelythat reproductive isolating mechanisms would have come into play. Thesemechanisms may well have been behavioural (Graves 1991), and some partof the cultural elaboration of behaviourally modern populations may haveacted as exclusive species-recognition signals as well as playing a rolein intraspecific competition.(29) Such earliest BMH populationsinitially existed on the margins of the area occupied by Neanderthals,under the dual selective pressures of competition and adaptation tohyper-arid conditions. The key to this BMH `dry-selected'adaptation was increased residential mobility, and also the exchange ofcritical information, resources and personnel as groups encountered eachother more frequently and over greater distances (cf. Marks 1983; 1990).Communication and negotiation would have been at a premium -- perhapsmaking use of skills which initially evolved for other reasons. The first Upper Palaeolithic sites are notably ephemeral bycomparison both with Mousterian and Epipalaeolithic ones. This mobilityexplains the consistent choice of curated tools made on blades: althoughthe potential for blade-manufacture was inherent in Middle Palaeolithicprepared-core technologies (for making hafted tools),(30) its consistentapplication began because of the economy and portability of bladeassemblages in more mobile patterns of land-use. String, baskets andnets may also date from this time. Mobility, curation and the exchangeof high-quality materials were thus closely related, and this networkseems to have begun in the marginal area of the Negev at a time whenMousterian assemblages still predominated in the Mediterranean zone ofthe Levant (Gilead 1991).(31) The earliest application of bladetechnology (approximately 50-40,000 b.p.) was for projectile projectilesomething thrown forward.projectile syringesee blow dart.projectile vomitingforceful vomiting, usually without preceding retching, in which the vomitus is thrown well forward. armatures(Emireh points); industries with plentiful knives and bone piercingtools, like the Aurignacian, may have developed further north in theLevant in connection with making skin clothing -- which gave BMHpopulations the ability to compete with Neanderthals around the northernMediterranean and Black Sea. `Art' and items procured bylong-distance trade became more common at this time (approximately40-30,000 b.p.). It is not clear whether transitions from AMH to BMHtook place independently elsewhere; but in the Levant it may reasonablybe claimed that these two elements -- adaptation to desiccation andcomplementary differentiation from Neanderthal populations -- togetherfuelled the critical transition to behavioural (and perhaps cognitive)modernity.(32) Climatic change is part of the story of the emergence ofsymbolic systems, too; and it was these symbolic systems which madepossible new responses to climatic cycles. Environmental change is not simply a backdrop to evolution: it isa principal reason for major episodes of biological change. It is nocoincidence that successive species of hominid made their appearanceduring the Quaternary Period, with its rapid pace and massive scale ofenvironmental alternation. Over 90% of this period has been cooler anddryer than the Holocene, so contemporary conditions areunrepresentative Adj. 1. unrepresentative - not exemplifying a class; "I soon tumbled to the fact that my weekends were atypical"; "behavior quite unrepresentative (or atypical) of the profession" . Although colloquially col��lo��qui��al?adj.1. Characteristic of or appropriate to the spoken language or to writing that seeks the effect of speech; informal.2. Relating to conversation; conversational. termed the (high latitude) `IceAge', it could equally appropriately be called the (low latitude)`Desert Age', especially -- from a human point of view -- sinceincreasing and cyclically enforced desiccation has been the principaldriving force of hominid evolution. The beginning of farming wasarguably the last revolutionary episode in human history where thisclimatic forcing played a critical role: the Human Revolution and theNeolithic Revolution were the last two thresholds in the transition fromclimate to culture as the principal triggers of change. Desiccationprecipitated modern behaviour, which (after some dampness and then alittle more desiccation) precipitated farming -- a socio-subsistencesystem which thereafter spread like an epidemic. Agriculture was anaccident waiting to happen (and it is scarcely surprising that ithappened so soon in the Levant): it was a logical continuation ofprocesses already in play; but farming itself created suchenvironmental, demographic and social instability that it gave rise toautocatalytic au��to��ca��tal��y��sis?n. pl. au��to��ca��tal��y��sesCatalysis of a chemical reaction by one of the products of the reaction.au processes of change -- the emergence of `nuclearareas', first in the Levant and then elsewhere.(33) Conclusion: recognizing the centresSpatial centricity is the counterpart of temporal punctuation:unusual events take place in unusual settings. It is arguable that eachof the great `revolutions' -- the Human (Upper Palaeolithic),Neolithic and Urban Revolutions, as well as the subsequent appearance ofthe world's first empires and the three most influentialworld-religions -- took place on the same portion of the Earth'ssurface. (Indeed, in Pleistocene perspective, these become episodes inthe same transformation.) This in itself argues for some remarkablegeographical properties, which are worth trying to define (Sherratt1996: 134-7). In topographical terms, the Levant (like Mesoamerica,though with a different climate) is a narrow isthmus isthmus(ĭs`məs), narrow neck of land connecting two larger land areas. Since it commands the only land route between two large areas and is on two seas, an isthmus has great strategical and commercial importance and is a favorable situation between twocontinental landmasses (the Fertile Crescent actually follows the plateboundary), fissured by northward extensions of the East African riftsystem. Situated between Africa and Asia (important in prehistory prehistory,period of human evolution before writing was invented and records kept. The term was coined by Daniel Wilson in 1851. It is followed by protohistory, the period for which we have some records but must still rely largely on archaeological evidence to ), andbetween the maritime provinces of the Mediterranean and the Indian Ocean(increasingly important in historic times), this funnel-like structureis thus both a transitional area and a crossroads. These features havefocussed demographic pressure and the density of human contacts with anexceptional intensity. In interglacials, its mountain chains serve tocatch the rain-bearing westerlies which penetrate along theMediterranean, turning an otherwise largely arid landscape into a seriesof wooded mountains and oases, backed by desert. This gives the regionits reticulate re��tic��u��late?adj.Resembling or forming a net or network: reticulate veins of a leaf.v. re��tic��u��lat��ed, re��tic��u��lat��ing, re��tic��u��latesv.tr.1. aspect: not just stark environmental contrasts but theirintimate admixture, providing refuges and opportunities for unusualconjunctions -- all subjected to rapid and large-scale climatic changes.Variation in time can thus only be understood in conjunction withvariation in space: change occurred in particular circumstances and inparticular places. Geography is the key to understanding these focalareas, critical for biological as much as for cultural evolution. Thejunction between northeast Africa and southwest Asia arguably became afocus of human development in the Late Pleistocene, saw the firsttransition to culture-driven change at the beginning of the Holocene,and remained central to human affairs until the 16th century AD. Few of the points raised in this paper are new ones; but it isremarkable that the pattern which they make has not so far beenemphasized, or made the focus of discussion. The reason must surely liein institutional politics: prehistory's attempt to distance itselffrom the traditional historical disciplines, with their bias towards theolder civilizations of the Old World. In trying to avoid potential bias,however, and trying -- often from the best of motives -- to give otherareas their chance, a subtle distortion of narrative has beenintroduced, and a story has been constructed which deliberately avoidsemphasizing the centrality of this focal area (cf. Gamble 1993).However, if punctuation really is the appropriate description of the(pre) historical process, then it will also be necessary to re-introduceits spatial dimension, centricity. The model of cores and peripheries isnot confined to later history, but has its beginning in the biologicalprocesses by which humanity emerged.(34)Acknowledgements. I must thank Tjeerd van Andel. Peter Bellwood,Cyprian Broodbank, Robert Hedges, Alison Roberts, and especially StephenStokes, for timely advice. The archaeological observations on whichthese arguments are based owe a great deal to the work of OferBar-Yosef.(1) The phrase was used in Cambridge Tripos papers in the late 1960s,though its authorship was unattributed un��at��trib��ut��ed?adj.Not attributed to a source, creator, or possessor: an unattributed opinion..(2) Named after a pollen-zone originally defined in Scandinavia,called after Dryas octopetala, the mountain avens avensAny of the low-growing, perennial flowering plants (approximately 50 species) of the genus Geum, in the rose family. Most occur in the northern or southern temperate zones or in the Arctic. : for a recent surveysee Troelstra et al. (1995).(3) Some idea of the earlier course of the atmospheric radiocarboncurve is provided by geomagnetic intensity measurements (Laj et al,1996: reference from T. van Andel).(4) With long, continuous records such as those provided for marinetemperatures by changing oxygen-isotope ratios in deep-sea cores, it ispossible to 'tune' the pattern of temperature fluctuations byreference to the astronomical predictions, providing an effectivelong-term calibration (Martinson et al. 1987).(5) This in itself causes problems, since it is consequently on theinterface between research communities which use BP and those which useBC, and those which calibrate To adjust or bring into balance. Scanners, CRTs and similar peripherals may require periodic adjustment. Unlike digital devices, the electronic components within these analog devices may change from their original specification. See color calibration and tweak. and those which don't: four differentways of referring to a date is a recipe for confusion.(6) Interestingly, instabilities of this magnitude have not so faroccurred during the Holocene; and nor (as was initially thought) werethey characteristic of the previous interglacial (OIS Noun 1. OIS - agency that oversees the intelligence relationships of the Treasury's offices and bureaus and provides a link between the Intelligence Community and officials responsible for international economic policyOffice of Intelligence Support 5), either.(7) This demonstrates that diagrams in adjacent regions -- Greece,Turkey, the Levant -- are largely in phase (i.e. responding to commonclimatic changes) rather than being offset or alternating.(8) Desiccated materials of PPN PPN - Project-Programmer Number.A user-ID under TOPS-10 and its various mutant progeny at SAIL, BBN, CompuServe and elsewhere. Old-time hackers from the PDP-10 era sometimes use this to refer to user IDs on other systems as well. B date (8500-7000 BC)from the NahalHemar cave, southwest of the Dead Sea, show a range of mats, baskets,vessels, quivers, nets and small clothing textiles (Schick 1988); theirancestry reaches back to the Upper Palaeolithic, as indicated byGravettian incised interlace To illuminate a screen by displaying all odd lines in the frame first and then all even lines. Interlacing uses half frames per second (fields per second) rather than full frames per second. ornament, and clay impressions from Moravia(Adovasio et al. 1996).(9) Unlike areas such as Atlantic Europe, the use of maritime (andespecially littoral littoral/lit��to��ral/ (lit��ah-r'l) pertaining to the shore of a large body of water. littoralpertaining to the shore. ) resources was not a viable alternative, because ofthe narrow tidal range of the Mediterranean and the nature of thesouthern Levantine coastline: intensification of seed-gathering was theonly option for foragers under stress.(10) `Direct AMS AMS - Andrew Message System dates on maize from Mexico, the Greater Southwestand eastern North America show that previous estimates for the antiquityof maize agriculture at key sites are unsubstantiated' (Fritz 1994:305). In fact, the oldest directly dated specimen from Tehuacan is onlymid 4th millennium BC.(11) For instance, the Times atlas of world archaeology'sspread, entitled `First farmers in the Americas', deals with theArchaic period from 7000 to 2500 b.c., while the following spread isentitled `First villages of the Americas' and deals with theFormative period from 2500 to 500 b.c. (Scarre 1988: 208-11).(12) That is why the concept of the domus rightly received suchemphasis in Ian Hodder's recent account of the spread of farming(1991).(13) The term `houses' should in this context probably alsoinclude surrogate non-habitation structures, such as megalithic meg��a��lith?n.A very large stone used in various prehistoric architectures or monumental styles, notably in western Europe during the second millennium b.c. orearth-and-timber monuments, which provided comparable community foci inthe western parts of Europe.(14) The volume of residue is more critical than the shape of thehouses: PPN A houses are round, like Natufian ones, but have`tell-building' properties (largely because of their use ofmud-brick). The change from these relatively simple dwellings to morecomplex rectangular forms takes place in PPN B, over an area from Beidhain southern Jordan to southern Anatolia/northern Iraq (Byrd 1994).(15) Childe (1963: 63), following Huxley, who first used homotaxial(always occupying the same relative position in a sequence) andsystadial (representing the same stage in an evolutionary sequence) inhis Presidential Address to the Geological Society in 1862.(16) Large quantities of naturally sown cereal grains are lost torodent and harvester-ant predation predationForm of food getting in which one animal, the predator, eats an animal of another species, the prey, immediately after killing it or, in some cases, while it is still alive. Most predators are generalists; they eat a variety of prey species. .(17) Note that early Holocene summer temperatures were higher thantoday in the northern hemisphere because of orbital eccentricity, sothat spring growth would take advantage of rapidly rising warmthcoinciding with soil moisture.(18) Although sufficient to justify the effort, if such low-landlocations had other attractions, such as permanent water or positions ontrade routes -- or both, in the case of Jericho and Aswad.(19) Zohary has emphasized that the limited range of geneticpolymorphisms of the initial cereal crops, by comparison with wildpopulations, implies (for each crop species) `a single domesticationevent or at most by very few such events' (1996: 156).(20) A carbohydrate crop needs to be cultivated, probably for sometime, before means for the saccharification of starch are discovered,and hence the possibility of producing fermented drinks. Whilebeer-production may have been a reason for the later spread of somecereal crops, this is unlikely to have been a reason for their primarydomestication.(21) Coriander has been identified from PPN B levels in the NahalHemar cave, Israel, but the association needs to be confirmed byradiocarbon dating.(22) The Kebaran site of Ohalo II, c. 18,000 BC, on the Sea ofGalilee Galilee(găl`ĭlē), region, N Israel, roughly the portion north of the plain of Esdraelon. Galilee was the chief scene of the ministry of Jesus. has produced exceptionally well preserved organic materials,including wild emmer and barley: see Kislev et al. (1992).(23) Either because of the penetration of depression-tracks along themediterranean, or because of enhanced monsoonal rainfall controlled bythe precessional cycle, which brought increased summer insolation to thenorthern hemisphere (see Wright 1993; Roberts and Wright 1994).(24) Hence the popularity of gardening as a hobby. This is in part adisplacement of social categories onto plants, a classic example of thecognitive procedures and analogical reasoning of Homo sapiens sapiens sa��pi��ens?adj.Of, relating to, or characteristic of Homo sapiens.[Latin sapi .(25) Matthew Spriggs (1996:525) has recently made this point inrelation to Melanesia: between foraging and farming `there is only oneimportant threshold . . . that between cultivation and agriculture.Foraging to wild plant-food production is certainly a continuum.'(26) The equation is not an exact one, for while glaciation islargely controlled by orbital eccentricity, the low-latitude moisturebudget is also affected by precession of the axis; and the two curves,having different periodicities, are not in synchrony synchrony/syn��chro��ny/ (-krah-ne) the occurrence of two events simultaneously or with a fixed time interval between them.atrioventricular (AV) synchrony . Thus the earlyHolocene was relatively wet in the tropics, becoming dryer after 4000BC; though this cannot be generalized for every interglacial.(27) Deserts extended in the last glaciation (the southern margin ofthe Sahara extending further south by up to 1000 km, for instance);tropical forests shrank, as did temperate and boreal bo��re��al?adj.1. Of or relating to the north; northern.2. Of or concerning the north wind.3. Boreal ones to leaveextensive areas of Artemisia Artemisia, ruler of CariaArtemisia(är'təmĭ`shēə), fl. 4th cent. B.C., ruler of the ancient region of Caria. She was the sister, wife, and successor of Mausolus and erected the mausoleum at Halicarnassus in his memory. steppe and tundra (see e.g. Street 1980).(28) These adaptations may have been quite radical, includinghairiness, subcutaneous fat, and even (dare one speculate?) hibernation.(The latter habit, if it was associated with `sleeping-hollows'filled with insulating vegetation, would mimic burials if theiroccupants did not survive the winter, and in some cases weredeliberately covered by later inhabitants of the cave).(29) Upper Palaeolithic string skirts, body-painting and the wearingof shell beads have an obvious connection with sex. It is interestingthat `clothing' may have evolved as a symbol before it was appliedas a survival technology (classic description in Barber 1991: 255-8) --another example of `luxuries before commodities'.(30) Blade-using assemblages had from time to time made a precociousappearance, as in the Amudian facies facies/fa��ci��es/ (fa��she-ez) pl. fa��cies ? [L.]1. the face.2. surface; the outer aspect of a body part or organ.3. expression (1). (e.g. Tabun layer E) at an earlystage of the Middle Palaeolithic, perhaps suggesting an earlier responseto such pressures.(31) Narratologists will recognize a similarity in plot to the Exodusstory, with Neanderthals instead of Canaanites; indeed, the key site ofBoker Tachtit (Marks 1983: 67-84) lies in the Wilderness of Zin, whereMoses struck water from the rocky.(32) This raises the important question of whether the BMH`revolution' was a neurological one, involving Darwinian selection,or a cultural one, revealing potentials and integrating behaviouralpatterns that were already present. If the former, it is important notto conceptualize con��cep��tu��al��ize?v. con��cep��tu��al��ized, con��cep��tu��al��iz��ing, con��cep��tu��al��iz��esv.tr.To form a concept or concepts of, and especially to interpret in a conceptual way: it in terms of intentionality intentionalityProperty of being directed toward an object. Intentionality is exhibited in various mental phenomena. Thus, if a person experiences an emotion toward an object, he has an intentional attitude toward it. (and thus, in effect,orthogenesis): i.e. to imagine it as a `human' response to a`problem'. The striking historical consequences of an innovationare often the unexpected side-effects from an initially unrelatedchange.(33) Did an independent Late Pleistocene transition from AMH to BMHtake place in east Asia?(34) Applying these ideas systematically will require abandonment ofthe premise of local autonomy, and more serious attention to thecomplementary large-scale processes of spatial expansion, recentlyunfashionable because of their lack of theoretical underpinnings:phenomena involving the spread of people, organisms, technologies, andnetworks of interaction (Sherratt 1995). It is time to re-thinkdiffusionism. References(Only a selection of recent synthetic sources for these vast topicsis cited; special reference should be made e.g. to Harris (1996), Lowe& Walker (I 997) and Levy (1995), and bibliographies therein.)Adovasio, J.M., O. Soffer & B. Klima. 1996. Upper Palaeolithicfibre technology from Pavlov I, Czech Republic, Antiquity 70: 526-34.Aitken, M.J. 1990. 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