Socioecological dynamics at the time of Neolithic transition in Iberia

AEA 2012 Conference Reading:Socioecological dynamics at the time ofNeolithic transition in IberiaJoan Bernabeu1, Oreto García Puchol*1, Salvador Pardo1, Michael Barton2,Sarah B. McClure3

1Departament de Prehistòria i Arqueologia, Universitat de València, Valencia, Spain, 2Center for SocialDynamics & Complexity, School of Anthropology, Arizona State University,Tempe, USA, 3Department ofAnthropology, Pennsylvania State University, USA

The Western Mediterranean, spanning southern Italy to Portugal, can be considered a single archaeologicalunit where the diagnostic characteristics of Early Neolithic contexts share common elements, marked by thespread of Cardium-Impressed ceramics. Although some consensus exists regarding the origin of thesewares in southern Italy, the debate surrounding its process of expansion to the west remains open. Iberiais a key region for the analysis of the neolithisation process due to its location at the end of the NeolithicMediterranean expansion. This view includes the problems linked with the mechanism of this spread andthe evolutionary dynamics of the early agricultural societies. Our goals are to evaluate the richarchaeological and palaeoenvironmental database produced by recent decades of research in this areain order to address issues related to the Neolithic Transition. We especially deal with the role played byclimatic events in the observed dynamics of the last Mesolithic and the Early Neolithic (ca. 8500–6900 cal BP).

Keywords: Late Mesolithic, Early Neolithic, 14C, Socio-ecological dynamics, Neolithisation

IntroductionThe transformation of subsistence systems fromhunting and gathering to farming involved a crucialchange to the relationship between humans and theenvironment, and affected all levels of humansociety. Perhaps for this reason, the issue of theorigin and expansion of Neolithic economies remainsa major topic in the archaeological and anthropologi-cal literature. In Europe, the origin of farming societiesis fundamentally concerned with the nature of theirdissemination.Current archaeological data suggest two primary

routes taken by the spread of agriculture in Europe:along the Danube River corridor from the Balkansto the North Sea and around the Mediterraneanlittoral.The western Mediterranean can be considered a

single archaeological unit where the diagnostic fea-tures of Early Neolithic contexts share certaincommon elements, delineated by the spread ofCardium-Impressed pottery wares. Some consensusexists regarding the origin of these wares in southernItaly, but the debate surrounding its process of

expansion to the west remains open (Zeder 2008),most particularly in Iberia (see Bernabeu 1999, 2002;Guilaine 2001; Zilhão 2001, 2003, 2011; Guilaineand Manen 2007; Bernabeu and Martí 2014; but seealso, Diaz del Rio 2011; Cruz Berrocal 2012). In thispaper we explore the socioecological dynamics of theNeolithic transition in Iberia within an extensive andhigh-resolution chronological framework builtmainly in recent years.

We focus here on temporal and spatial distributionsof human occupation in the Iberian peninsula spanningthe Neolithic transition, from last hunters–gatherers groups (characterised by the appearance ofbladelet technology with trapezes and trianglesaround 8500 cal BP) to the end of Early Neolithic(ca. 7100–6900 cal BP). Special attention is paid tothe role of climatic events in social and economicchange. All dates in the text are expressed in cal BP.To facilitate comprehension, the chronological scalesof the figures are represented in both cal BP and cal BC.

Material and MethodsIberian Chronological DatasetOur work draws from a database which contains infor-mation about: (a) sites and their locations; and (b)radiocarbon dates with indication of dated samples

Correspondence to: Oreto García Puchol, Departament de Prehistòria iArqueologia, Universitat de Valencia, Av. Blasco Ibañez 28, 46010Valencia, Spain. Email: [email protected]

© Association for Environmental Archaeology 2014DOI 10.1179/1749631414Y.0000000032 Environmental Archaeology 2014 VOL. 19 NO. 3214

mailto:[email protected]



and the contexts with which they are associated. Thisdatabase has its origins in a compilation made in thecontext of a recent research project (seeAcknowledgements) for southern Spain, and hasbeen expanded by consulting various other syntheses(Castro et al. 1996; Juan Cabanilles and Martí 2002;Bernabeu 2006; Carvalho 2008; Alday 2009; Rojoet al. 2012; see details in supplementary materials).These archaeological and chronological data

encompass the entire Iberian Peninsula except for thenorthern (Cantabrian) region, where current infor-mation indicates that agriculture began later than thetime range of interest here – i.e. ca. 8000 and 5500BP (ca. 8800–6300 cal BP). A total of 713 datesclearly associated with Mesolithic and/or EarlyNeolithic contexts comprise the collected sample.From these, we exclude dates obtained on bones

with evidence of burning, because there can be signifi-cant differences between dates from burnt and charredbones, compared with unburnt bone (Olsen et al. 2008,798). Dates from marine samples also have been dis-carded because of potential fluctuations in the reser-voir effect in relation to space and time that lead touncertainty in the accuracy of the dating estimates(Ascough et al. 2005). From the original 713 dates,we base the analysis here on a total of 558 14C datesfrom 144 sites as shown in Table 1.

Sample SelectionWe divided the radiocarbon dates into those obtainedfrom wood charcoal, from short-lived plant speciesand/or animals bones and from domestic plant and/or animal remains. In many cases, published 14Cdates do not provide critical information about con-texts and samples from which they were obtained.However, it is well known that both factors mayhave important impacts (see Bernabeu et al. 2001;

Zilhão 2001, 2011; Bernabeu 2006). For example,charcoal dates may be subject to the ‘old woodeffect’, in which the date obtained is significantlyolder than the archaeological context being dated, ascan be seen in Fig. 1. Clearly the curve made fromlong-lived samples shows a wider and olderdistribution compared with the curve derived fromshort-lived samples. With the sample used here,when combining both short- and long-lived samples,the resulting curve showed a mixed pattern, clearlydifferent from short-lived curve. Differences betweenthe two curves arise not only from the ‘old woodeffect’, but also reflects the distance between those(bones/seeds) most directly associated with humanactivity in the place of those that may reflect otherevents (e.g. scattered pieces of charcoal coming fromwildfires).Because we are interested in the relationships

between human and environmental dynamics, in thispaper we only use radiocarbon dates obtained fromthe following kinds of samples:(a) Short-lived samples of singular events directly

associated with Mesolithic or Neolithic occupation(bones with anthropogenic signs, human bones,seeds, fruits or bone artefacts) or charcoal clearlyidentified.

(b) Short-lived aggregates made up of items from any ofthe previous classes.

This resulted in a final sample size of 313 radiocar-bon dates. There are 89 samples corresponding to 34Mesolithic sites and 224 from 75 Neolithic sites. Asample was considered Neolithic if it is associated toa level containing remains of domestic animals orplants (Table 1).The distribution of these sites is not necessarily

representative of the distribution of prehistoric

Table 1 List of dated samples used by material and region

Total long-lived 247

Mesolithic Neolithic

Charcoal Other Total Charcoal Other Total

Upper/middle Duero 9 9Guadiana/Guadalquivir 6 6Upper/middle Tajo 19 19Ebro 4 4 66 66Portugal 19 19 17 17Northeast 4 4 26 26East-southeast 14 14 57 6 63Total 41 41 200 6 206

Total long-lived 311 Bone Seed/fruit Other Total Bone Seed/fruit Other TotalUpper/middle Duero 4 7 11Guadiana/Guadalquivir 2 21 23Upper/middle Tajo 8 1 9Ebro 30 1 31 37 9 46Portugal 30 1 31 27 2 29Northeast 19 15 34East-southeast 20 6 2 28 42 23 4 69Total 80 8 2 90 139 76 6 221

Bernabeu et al. Socioecological dynamics at the time of Neolithic transition in Iberia

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human occupation, and in fact is attributable in part tothe locations of archaeological research programs.Nevertheless, the database of dated sites extends overmost of the Iberian Peninsula (Fig. 2), making ituseful for broad generalisations about the Neolithictransition.

Summed Radiocarbon Probability DistributionsMany archaeological studies use summed radiocarbonprobability distributions (sumprob) as a proxy for pre-historic occupation (Gamble et al. 2005; Shennan andEdinborough 2007; Fiorentino et al. 2013), althoughthere are reasons to be cautious in the interpretationof the results (Bamforth and Grund 2012; Williams2012). The working assumption of such a sumprobanalysis is that multiple small, unsystematic samplesfrom a large assemblage of sites constitute a quasi-random sample of regional occupation trends. Prioranalyses of the temporal variability of the sum of prob-abilities suggest that representativeness depends on thesample size, which in turn is related to the averagestandard deviation (ΔT) of the dates and a timelength of the analysed period (Michczynska andPazdur 2004; Williams 2012). Although Williams(2012) suggests a sample size of between 200 and 500dates to obtain robust statistical results, the standarddeviation found in that case is much higher (170)

than ours (∼50), and the time length covered is con-siderably broader (50·0 ka vs. 2 ka).

We are aware that reducing the number of radiocar-bon dates (314) affects the value of sumprob, but this isbalanced by a significant reduction in ΔT within alimited chronological time span. We use the summedradiocarbon probability distributions at two differentscales, Iberia as a whole and selected regional areaswith sufficient data (see Fig. 2), in order to investigatehow local–regional dynamics compared with globalpatterns. We emphasize that the sumprob is used asa method to observe trends, and not as a strict demo-graphic proxy. All sumprob curves were producedusing Calib (version 6.10) with calibration CurveINTCAL09 (Reimer et al. 2009).

Certainly the use of Bayesian approaches to model-ling radiocarbon chronologies (Bayliss et al. 2007;Whittle et al. 2007, 2011) can provide useful results,as well as provide more accurate dates for surface col-lections (Fernández-López de Pablo and Barton2013). Nevertheless, our intention here is to observeand compare trends between archaeological andenvironmental data, and the only boundary used isdefined by the presence of domestic resources. In our

Figure 1 Sumprob distribution of dated samples at theNeolithic sites of the Ambrona valley (data from Rojo et al.2008). Clearly the old wood effect is visible: the curve madefrom long-lived samples shows a wider and older distributioncompared with those obtained from short lived samples. Withthe sample size used here, when merging both, short- andlong-lived samples, the resulting curve shows a mixedpattern, clearly different from short lived curve.

Figure 2 Distribution of radiocarbon sites density (long-livedand short-lived). (A) Upper map represents Mesolithic sites,and also are represented the regional areas. (B) Lower maprepresents Neolithic sites.


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opinion the use of the sumprob may be a good tool fora first approach to the problems addressed here.

Discussion: Socieoecological Dynamics ofNeolithic TransitionThe sumprob data in Fig. 3 suggest several thingsabout the timing of the Neolithic transition at thescale of the entire Iberian Peninsula. First, there areclear regular temporal oscillations in the Mesolithicradiocarbon data. Second, the date of the initialNeolithic in Iberia cannot be traced back beyond7650–7600 cal BP. Following this, there is a clearincrease in Neolithic dates and a progressive decreaseof those from Mesolithic contexts. Finally, at the endof the eighth millennium cal BP, there is a significantfall-off in the sumprob curve. We examine the inter-actions between cultural dynamics and climaticevents to account for these patterns in the radiocarbondata, and suggest implications of these interactions inthe Iberian Peninsula at global and regional scales.

Global Climatic Events and Local Proxies (Earlyand Middle Holocene)Environmental changes resulting from climatic eventsand geomorphological shifts have had an importantimpact in human life. Several recent studies havesuggested that the 8·2 ka BP climatic event played animportant role in the expansion of the Neolithic toEurope, including the western Mediterranean(Weninger et al. 2006; Berger and Guilaine 2009).This event is attributed to changes in salinity in theNorth Atlantic, due to fresh water outbursts causedby Laurentide ice sheet collapse and iceberg discharges(IRD Holocene events) (Gronenborg 2009; Fig. 4A).Berger and Guilaine (2009) compared archaeologicaland climatic records around the Mediterranean

basin, and suggest the 8·2 ka event might have tapho-nomic impacts on the archaeological record of the lasthunter–gatherers and first agriculturalists, especiallyfor sites located in valley bottoms and karst areas,that could help explain gaps in the record ofthe Neolithic transition. Several such gaps in theMesolithic record of southern France and theIberian Mediterranean coast could be explained inthis way, and the authors note the need for an accurateradiocarbon dataset as a primary basis for recon-structed regional models.Other climatic fluctuations, such as the 7·1 ka cal

BP event, have been mentioned in relation with thedecline of LBK culture in central Europe(Gronenborn 2009). Gronenborn (2009) also suggestspotential causal links between several other global cli-matic events of the early and middle Holocene andmajor episodes of cultural change – particularlyshort episodes of cooler and drier conditions. Theregional consequences of these global events canvary depending on latitude and other geographicalvariables (Fig. 4).Several studies in the Iberian Peninsula examine the

impact of climatic events in the early and middleHolocene on regional and/or micro-regional pro-cesses, arriving at different interpretations of the evi-dence (Fernández and Gómez Puche 2009; Gonzálezet al. 2009; Cortés et al. 2012). Frigola et al. (2007)and González et al. (2009) suggest that local climaticproxies and stratigraphic archaeological data in theBajo Aragon (in the lower Ebro) indicate a correlationbetween the abrupt climatic episode of the 8·2 ka eventand a gap in the most important local archaeologicalsequences, based on 14C data between 8 and 7·3 kaBP. Cortés et al. (2012) discuss the possible impactsof changes in maritime and continental ecosystemsalong southern Iberian coast on Mesolithic retreatand the subsequent maritime Neolithic expansion.From a compilation of marine and continentalpalaeoenvironmental records, they suggest that the8·2 ka event does not have significant climaticimpacts in this region. Rather, more notable environ-mental changes are recorded between 7·8 and 7·3 kaBP (Fig. 4B), when several climatic proxies indicatean increase in aridity and important changes in ther-mohaline circulation in western Mediterranean.Pollen and charcoal analysis from some sites points

to a gentler Holocene climate for Iberia as a whole,with a gradual increase in tree cover reaching itsmaximum proportions during the Atlantic chronozone(Quercus replacing Pinus and Juniperus) (see Carriónet al. 2010). The ecological consequences of the earlyHolocene rise in sea level are hard to evaluate, but itis likely that coastal sites could now lie beneath the sea.In addition to the 8·2 ka event, other climatic events

have been identified in the early Holocene record,Figure 3 Comparison of Sumprob distributions of Mesolithicand Neolithic dates from Iberia.



between 7100 and 5500 cal BP (Fig. 4C). Of these, theepisode at ca. 7100–6900 cal BP is of particular inter-est here. Coinciding with the IRD 5b, it seems to cor-relate with what has been identified as a period of crisisand transformation of the Early Neolithic.

The Mesolithic PreludeThe final Mesolithic in Iberian Peninsula is linked withbladelet technology and trapezes. This complex

initially appears around 8500 cal BP and extendsuntil mid-eighth millennium cal BP (Fig. 5). By theend of ninth millennium cal BP, there is a change inthe geometric microliths so that triangles predominate,with the Cocina-Muge type of the triangles commonacross the Mediterranean region and Portugal.Fig. 6A and B show several concentrations ofMesolithic sites (Ebro basin, East Mediterraneancoast and Atlantic Portugal), as well as spatial gaps

Figure 4 Climatic events. (A) Selected marine and terrestrial paleoclimate proxy-data for Central Europe (image fromGronenborn 2009), (B) Environmental proxies used in diverse paleorecords for the time interval 8·2–7·0 ka in Iberia (image fromCortés et al. 2012), (C) Comparison of different paleoclimate records for the Iberian Peninsula and western Mediterranean Seaspanning most of the last glacial period and the deglaciation (image from Cacho et al. 2010).



in the Mesolithic archaeological record (mainly in theCentral plateau and Catalonia). Cave sites with econ-omic specialisation, an increasing number of open-airsites, and the presence of multi-burial sites are themost characteristic, suggesting territorial stability.From a peninsular-wide perspective, we can observean overall increase in Mesolithic-associated radiocar-bon dates throughout this period. This increase isnot continuous, however, exhibiting alternatingperiods of growth and decline in the sumprob curve.Although at the scale of Iberia as a whole, there is ageneral co-occurrence between the 8·2 ka BP eventand a decrease in Mesolithic dates, this patternseems to vary from region to region (Fig. 5).Moreover, further distinctions emerge if we zoom in

on micro-regions, but more refined archaeological andchronological data are clearly needed. This is the caseof Bajo Aragon, a micro-region included in our Eastregion. A gap between 8 and 7·3 ka BP has been pro-posed (González et al. 2009), but does not seem

supported by the data we present here. Radiocarbondata show Mesolithic occupation within the proposedgap, and some of the sites have diagnostic elementstypical of the gap period elsewhere (i.e. layers withCocina-type triangles not well dated), as opposed toother regions (see point 3·4). For the Andalusianregion there is not yet sufficient radiocarbon andarchaeological data to evaluate possible climaticeffects on the relocation of Mesolithic settlementsand its subsequent role in the Neolithic expansion.Summarising, the general pattern of variability

observed could be better understood looking at thedistribution maps before and after 7900 cal BP(Fig. 6A and B). In fact, the primary climatic effectsonMesolithic systems could be limited to a minor relo-cation of settlements.

The Neolithic SpreadThe arrival of the first Neolithic groups is dated to7650–7600 cal BP at the earliest (Fig. 3). Their

Figure 5 Sumprob curves comparison between Iberian Mesolithic-Neolithic Sumprob and Regional Mesolithic-NeolithicSumprob (Ebro Valley, Portugal and the Eastern Iberia). Also represented are climatic events 8·2, 7·8–7·3 and 7·1.



territorial expansion was discontinuous but rapid,extending over coastal regions and some inland areasfollowing the course of the rivers in no more thantwo centuries (Bernabeu et al. 2009). This time spanleaves room to speculate on different regional andchronological distributions, but no greater chronologi-cal precision it is possible (Fig. 6B and C).The spread of the Neolithic progressively replaces

evidence for Mesolithic groups. At the peninsularlevel, Mesolithic occupation seems to decline in step-wise manner, with the largest initial drop in radiocar-bon record at ca. 7600 cal BP, a second rapid decline atca. 7400 cal BP and a final drop at ca. 7200 cal BP(Fig. 3). At a regional level, there is some variationin this overall pattern (Fig. 5). Step-wise declines areseen in the Ebro valley and in Portugal, with radiocar-bon evidence for Mesolithic occupation possiblyextending as much as 500 years after the initial appear-ance of the Neolithic. While this suggests the coexis-tence of Mesolithic and Neolithic groups, there is noevidence of exchanges in cultural materials betweensuch groups in Portugal (Zilhão 2001; but also see

Bicho et al. 2011 who shortens the period of coexis-tence). In the east of the Iberian Peninsula, on theother hand, radiocarbon evidence for the Mesolithicmay extend no more than 100 years after the arrivalof the Neolithic. Should these dates be confirmed,they suggest the operation of different modes of inter-action between prehistoric farmers and foragers, witha rapid neolithisation of Mesolithic groups in theeastern regions of Iberia. There is no evidence forfinal Mesolithic populations in Catalonia and thecentral Meseta, despite the numerous research projectsand excavations carried out over the past two decades.If this represents a real absence of Mesolithic occu-pation, the Neolithic expansion may be best rep-resented as a colonisation of largely emptylandscapes in these regions.

From ca. 7450 cal BP, the sumprob curve forNeolithic occupation rises rapidly to peak around7200 cal BP; after a brief period of stability, thecurve declines after ca. 7150 cal BP. During thisperiod, Neolithic villages are established and organisethe new territories that encompass cave sites, hunting

Figure 6 Distribution of sites with radiocarbon dates (short-lived). Red dots represent Neolithic sites, and blue dots representMesolithic sites. (A) Sites before 7900 cal BP, (B) sites between 7600 and 7450 cal BP, (C) sites between 7350 and 7050 cal BP,(D) sites between 6650 and 6550 cal BP.



grounds and rock art sanctuaries. Pottery styles definetwo major areas: the Cardial around the coast and theEpicardial inland (Fig. 6C). This suggests the develop-ment of geographically extensive social networkswithin which information and commodities flowed,affecting extensive regions at different scales andintensity.

Detecting Signals of Collapse at the End of theEarly NeolithicFollowing the initial period of rapid expansion, theradiocarbon record suggests a ‘collapse’ of Neolithicoccupation between the end of the eighth millenniumand the beginning of the seventh millennium cal BP(Fig. 3). At same time, pottery styles became moreregional, indicating some kind of fragmentation ofpreviously established networks. Could we relatethese changes with any climatic event? At the scaleof the Iberian peninsula, there is rough correspon-dence with the 7·1 ka event (Figs. 3 and 4). Butagain, there is regional variability in the chronologicalcoincidence between climatic events and radiocarbondates (Fig. 5). The difference between the Ebro andthe eastern regions is particularly interesting in thisregard. In the latter, the drop in sumprob for theNeolithic falls close to the beginning of the 7·1 kaevent, but in the Ebro it falls close to the end.Given these differences, we can examine the

relationships between global climate change and socio-ecological dynamics for the local scale at which humandecisions and action took place in the central region ofEastern Spain, between the Segura and Xúquer rivers(ca. 16·500 sq km), one of the most intensively studiedareas for the Neolithic transition in the Mediterraneancoast of Iberia (Fig. 7). Within this area, the SerpisValleys is a small region (ca. 1250 sq km) that hasbeen the focus of a collaborative research project forover two decades (Barton et al. 1999, 2002, 2004a,2004b; Bernabeu 1999; Bernabeu et al. 2000, 2006,2012; McClure et al. 2008, 2009; García et al. 2009;McClure 2011).Although the sample of radiocarbon dates is limited

compared with the peninsular and regional datasetsdiscussed previously, the long-term research effort inthese two areas allows us a detailed look at the inter-action of human and natural processes (Fig. 8). Inboth regions the 8·2 ka event coincides with a dramaticdecrease in radiocarbon probabilities for theMesolithic. Subsequently, there are two cycles ofincrease and decrease in Mesolithic sumprob valuesin the Segura-Xúquer, but a lack of Mesolithic radio-carbon dates for the Serpis drainage. The Mesolithicsample for the Serpis is half the size of that for theSegura-Xúquer, however, and a larger sample ofdated Mesolithic sites is needed to better assess thereality of this gap.

The sumprob curves for the Neolithic in both areasare nearly identical, however, suggesting they experi-enced the same temporal pattern of Neolithic occu-pation. Importantly, in neither case are there clearassociations between the Neolithic sumprob curvesand global climatic events. Comparing this scenariowith the one proposed for the Bajo Aragon, anotherregion of the east, the period between 7·8 and 7·3 kadid not have major effects on the Mesolithic retreator the Neolithic spread. The dynamics afterNeolithic consolidation do not differ betweenthe two regions, and it seems difficult to correlate thefall-off of both sumprob curves with either the7·8–7·3 or 7·1 ka events. Once again there is abroader coincidence that leaves room for ambiguousinterpretations. More precise data are needed.As an alternative to purely climate-driven changes

in Neolithic occupation, we can examine the dynamicsof land-use/landscape interactions of agriculturalcommunities over generations. A component of ourcollaborative work in the Serpis drainage is theMedLand project, designed to carry out compu-tational experiments on the long-term, recursive inter-actions between society, land-use and environmentalchange (Barton et al. 2010, 2012).Its results suggest that some kinds of agricultural

practices could have an expansive effect over small

Figure 7 Location of regional areas for the Eastern Iberia,the Xúquer-Segura region and Serpis Valley.



communities located at valley bottoms. But as com-munities grow past a locally determined thresholdsize, the consequences of identical land-use practiceschange, creating an imbalance between soil erosionand accumulation, with the potential for leaving acatchment unsuitable for farming over the long term.How might this kind of process have been respon-

sible for the changes described in the entire system?And how can we evaluate it? The answer to the firstquestion may lie on the strategies that can mitigatesuch environmental degradation as reducing commu-nity size through emigration or fission (colonisationof new areas), or, increasing the area devoted tograzing relative to cultivation. At the local-scale ofthe Serpis Valley, we found indications of suchchanges: the demographic growth and the increase ofthe scale and complexity of the socio-spatial networksthat characterise the period 7450–7150 cal BP stopped;there is a reorganisation of settlement patterns; at thesame time, some caves change their use, showing the

presence of thick corral layers suggesting a change inherding practices; and interregional exchange net-works disappeared (Bernabeu et al. 2006, 2012).These local shifts may have removed key groups (i.e.nodes) from regional social networks, potentiallyresulting in the fragmentation of networks establishedearlier, limiting the information flow over the entirenetwork and then modifying the system at a globalscale.

ConclusionSeveral recent studies propose a correlation and causalrelationship between climate and cultural changeduring the neolithisation of Europe, includingGronenborn (2009 and 2010) for central Europe, andCortés et al. (2012) for the Iberian Peninsula.Although it is not our intention to deny the possibleinfluences of climatic change in the socio-ecologicaldynamics, we want to stress some points based onthe discussion and analyses above.

Figure 8 Sumprob curves comparison between Xúquer-Segura Mesolithic-Neolithic (including Serpis valley) and Mesolithic-Neolithic Serpis Valley only. In this case (Serpis Valley) we can see the gap between Mesolithic and Neolithic.



Firstly, in the Iberian Peninsula, the interpretationof different paleoclimatic proxies in southernMediterranean and south Atlantic coast suggest thatthe 8·2 cal ka event had no direct impact on observedcultural change (Cortés et al. 2012). Rather, minorchanges in temperature (decrease of 1°C in theAlboran sea) and aridity only occur prior the periodbetween 7·8 and 7·3 cal ka BP when possible signalsof major aridity first appear. In contrast, in the caseof the Ebro valley, other authors mark the age range8100–7900 cal BP as the most probable for this coldevent (González et al. 2009).Other climatic fluctuations can be observed around

ca. 7100–6900 cal BP (maybe the IRD 5b?), but arenot well defined in the proxy record (Cacho et al.2010). Clearly, more information is required for clari-fying both the age span of the climatic events and theirregional effects.Secondly, the radiocarbon data used here are

limited. We can increase the sample by using datafrom charcoal, but this in turn will increase the noiseso that, at the end, it is possible that we are discussingmore the processes of formation of the radiocarbonsample than population dynamics. With the availabledata used here we only can note trends and suggestideas that should be evaluated in future work. Heretoo, more quantity and quality of data is needed ifwe want to understand the possible correlationsbetween climatic events and population dynamics.Third, dynamics of occupation/abandonment

affecting sites or regions are recurrent over time andexhibit regional variability (Fig. 5). Sometimes theymatch climatic events, but in other cases they do not.These cyclic dynamics seem more common in theMesolithic than in the Neolithic. Is this due to thesample size (smaller in the Mesolithic), or to the differ-ent economic strategies of hunter–gatherers and agri-culturalists? Moreover, there is a considerable degreeof regional variability. As we are looking to explaingeneral patterns of change, we need a way to under-stand how this local variability could result in theglobal patterns of change.Fourth, in any case, it is clear that the 8·2 ka event

had no consequences for the Neolithic spread inIberia, unless we can link it with the abandonmentof some regions (like the Serpis Valleys) that sub-sequently facilitate its occupation by newcomersseveral centuries later.The settlement gap proposed in the Bajo Aragon

does not seem well supported by data currently avail-able. For the Andalusian region, the current scarcityof Mesolithic data leaves ambiguous the potentialeffects in the relocation of settlements and their sub-sequent role in the Neolithic expansion. Moreover,the possible consequences of a dry period during7·8–7·3 ka are likewise ambiguous; the same seems

true for the period 7·1 ka that has been characterisedas a dry period in some works (Cacho et al. 2010).Both could be related with the collapse of the EarlyNeolithic in some way, but there is only a chancethat the later of these periods could have had effectslocally.Fifth, global climatic events may well have had con-

sequences for human societies, but they are regionallyand locally variable. This variation is due to differ-ences reflecting the importance of biotic factors andhuman economic behaviour, especially land use.Both factors are historically contingent with respectto long-term trends of the environment and theeffects of different land use on economic, demographicand cultural changes. What we need are not only new,high-quality, well-dated and high-resolution multi-proxy records both of human and environmental con-ditions, but a way to understand how different localdynamics could result in global patterns of change,those we are looking to explain.

AcknowledgementsThis work was supported by the research projects ofgovernment of Spain HAR2009-14360-C03-01:‘Análisis comparativo de las dinámicassocioeconómicas en la Prehistoria reciente peninsular(VI-II milenios AC): la fachada mediterránea’ andHAR2012-33111 ‘MESO COCINA: los últimoscaza-recolectores y el paradigma de la neolitizaciónen el mediterráneo peninsular’. Collaborative researchin eastern Spain and the Mediterranean LandscapeDynamics project were supported by NationalScience Foundation grants: BCS-0075292,BCS-0331583, BCS-0122866, BNS-9115209, SBR-9904050, BCS-410269, BCS-638879, and BCS-543848.

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Socioecological dynamics at the time of Neolithic transition in Iberia

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