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Chronology of Ksar Akil (Lebanon) and Implications forthe Colonization of Europe by Anatomically ModernHumans

Katerina Douka1*, Christopher A. Bergman2, Robert E. M. Hedges1, Frank P. Wesselingh3,

Thomas F. G. Higham1

1 Oxford Radiocarbon Accelerator Unit, Research Laboratory for Archaeology and the History of Art, University of Oxford, Oxford, United Kingdom, 2 URS Corporation,

Cincinnati, Ohio, United States of America, 3 Naturalis Biodiversity Center, Leiden, The Netherlands

Abstract

The Out-of-Africa model holds that anatomically modern humans (AMH) evolved and dispersed from Africa into Asia, andlater Europe. Palaeoanthropological evidence from the Near East assumes great importance, but AMH remains from theregion are extremely scarce. Egbert, a now-lost AMH fossil from the key site of Ksar Akil (Lebanon) and Ethelruda, arecently re-discovered fragmentary maxilla from the same site, are two rare examples where human fossils are directlylinked with early Upper Palaeolithic archaeological assemblages. Here we radiocarbon date the contexts from which Egbertand Ethelruda were recovered, as well as the levels above and below the findspots. In the absence of well-preserved organicmaterials, we primarily used marine shell beads, often regarded as indicative of behavioural modernity. Bayesian modellingallows for the construction of a chronostratigraphic framework for Ksar Akil, which supports several conclusions. The model-generated age estimates place Egbert between 40.839.2 ka cal BP (68.2% prob.) and Ethelruda between 42.441.7 ka calBP (68.2% prob.). This indicates that Egbert is of an age comparable to that of the oldest directly-dated European AMH(Pestera cu Oase). Ethelruda is older, but on current estimates not older than the modern human teeth from Cavallo in Italy.The dating of the so-called transitional or Initial Upper Palaeolithic layers of the site may indicate that the passage fromthe Middle to Upper Palaeolithic at Ksar Akil, and possibly in the wider northern Levant, occurred later than previouslyestimated, casting some doubts on the assumed singular role of the region as a locus for human dispersals into Europe.Finally, tentative interpretations of the fossils taxonomy, combined with the chronometric dating of Ethelrudas context,provides evidence that the transitional/IUP industries of Europe and the Levant, or at least some of them, may be the resultof early modern human migration(s).

Citation:Douka K, Bergman CA, Hedges REM, Wesselingh FP, Higham TFG (2013) Chronology of Ksar Akil (Lebanon) and Implications for the Colonization ofEurope by Anatomically Modern Humans. PLoS ONE 8(9): e72931. doi:10.1371/journal.pone.0072931

Editor:Carles Lalueza-Fox, Institut de Biologia Evolutiva Universitat Pompeu Fabra, Spain

ReceivedMay 9, 2013; Accepted July 15, 2013; Published September 11, 2013

Copyright: 2013 Douka et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits

unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Funding:The dating component of this research was funded by a NERC-NRCF (UK) grant (NF/2008/2/2). During the period this work was undertaken, KD wasfunded by the State Scholarships Foundation (I.K.Y., Greece/www.iky.gr) and the A.G. Leventis Foundation (www.leventisfoundation.org) with two separatepostgraduate scholarships. KD and TFGH are members of the European Research Council Grant PALAECHRON (ERC-2012-AdG324139). The funders had no rolein study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests:Dr. Christopher Bergman works as a consultant for a private corporation, URS. All of his research for this article was conducted between1976 and 1985, while a student at the American University of Beirut and the University of London. All work on this article was conducted entirely outside of hisactivities at URS. Dr. Bergman is not aware of any conflicts or competing interests related to his involvement in this article. This does not alter the authorsadherence to all the PLOS ONE policies on sharing data and materials.

* E-mail: [email protected]

Introduction

Significant changes in human behaviour, cognition and

innovation become sharply evident in the archaeological record

of Eurasia at 45,000 years BP and demarcate the end of theMiddle Palaeolithic and the onset of the Upper Palaeolithic

period. The material cultures associated with the latter include the

so-called transitional technocomplexes (e.g., the Chatelperro-

nian of Franco-Cantabria, the Uluzzian of Italy and the

Bachokirian of Bulgaria), and the subsequent Early Upper

Palaeolithic (EUP) technocomplexes, namely the (Proto- and

Early) Aurignacian found throughout the continent. In the Eastern

Mediterranean region (hereafter, the Levant) the earliest Upper

Palaeolithic includes the Emiran and Initial Upper Palaeolithic

(IUP) entities, and the succeeding EUP, locally known as the Early

Ahmarian, technocomplex. When compared to the Middle

Palaeolithic record, these technocomplexes exhibit technological

and typological diversification in stone tools made on blades,

occasional production of organic implements from bone and

antler, and importantly, the sudden appearance of personal

ornamentation in the form of marine shell beads. These were not

part of the behavioural package of previous human populations

(Neanderthals) living in the same region.

Transitional/IUP and EUP assemblages, both in Europe and

the Levant, have been attributed to the expansion of AMH and

the replacement of local Neanderthal populations [13], although

there are widely acknowledged limitations expressed in these

linkages [4,5], especially since there is such scanty fossil evidence

in association. In addition to being extremely rare, human fossils

from the period are usually fragmentary and difficult to

characterize morphologically with certainty [6,7], in some cases

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they lack an archaeological context (e.g., as at Pestera cu Oase),

and/or are intrusive and of much younger (Holocene) age [8,9].

Recently, the initial colonization of Europe by AMH has been

shown to be earlier than previously thought, dating to ,43

45,000 BP, or even earlier [10,11]. This early presence, along with

subsequent and probably more substantial movements of AMH

towards Europe, e.g., during the Aurignacian, are thought to have

occurred along two different trajectories, both starting or passing

through the Near East [2,3] and following a path either along theMediterranean rim and/or up the Danube fluvial corridor.

The Levant represents a land bridge connecting Africa, Asia

and Europe [12] and has often been viewed as a region of high

palaeoanthropological significance, a starting point where one

might expect to find some of the earliest AMH fossils alongside

EUP assemblages [13], and possibly IUP assemblages, as well.

Indeed, important examples of human fossils in such contexts were

recovered 75 years ago at Ksar Akil in Lebanon. The site and the

fossils, however, lacked a secure absolute chronology, which is the

focus of the present paper. We believe these data may help furtherour understanding of the timing and geographic context of the

dispersal of AMH into Europe.

ContextKsar Akil is the reference Upper Palaeolithic site for the Near

East. It was excavated by the American Jesuits Doherty, Ewing,

and Murphy in 193738 and 194748 [14,15], and later by Tixier

between 19691975 [16] (Text S1 (SI Section I)). It contains a 23 mstratigraphic succession traditionally divided into 36 levels, I-

XXXVI from top to bottom (Fig. 1; see also Text S1 (SI Section I)).During the most recent excavations by Tixier, many more levels

and sub-divisions were established due to more advanced and

thorough recovery procedures. Unfortunately, Tixiers excavations

stopped before ever reaching the important IUP and EUP levels,

due to political instability in Lebanon in the mid-1970s.

The earliest occupation at Ksar Akil, from level XXXVI to level

XXVI at the base of the sequence, is of Middle Palaeolithic

(Mousterian) affinities ([1718]; see also Text S1 (SI Section I)). The

sequence continues with an intermediate archaeological phase,which represents the transition from the Middle to Upper

Palaeolithic period. Assemblages exhibiting similar characteristicsare currently referred to as IUP [1920]. At Ksar Akil, the IUP

phase occupies levels XXVXXI ([2122]; see also Text S1 (SISection I)). The subsequent archaeological levels XXXVI display ashift in some of the characteristics of material culture and lithic

assemblages towards a classic Upper Palaeolithic manifestation,

known as the Ahmarian, specifically the Northern facies of the

Early Ahmarian ([23]; see also Text S1 (SI Section I)). Levels XV

and XIV contain little evidence for human presence and are

thought to represent an occupational hiatus, possibly reflecting an

episode of intensive soil weathering during a wet climatic phase

[14,17]. The upper portion of the Ksar Akil sequence comprises

levels XIIIVI that span approximately 7.25 meters of deposit.

Previously referred to as Levantine Aurignacian A, B, and C [24],recent studies [2529] have avoided this descriptor due to a lack of

clarity surrounding what constitutes the Aurignacian presence in

the Levant. This upper portion of the Ksar Akil sequence is

stratigraphically and culturally complex and is summarized in

Text S1 (Section II), Table S1. It is very likely that the lower

portion is equally complex; however, detailed studies have not

been undertaken yet.

An interesting feature in the long stratigraphy of the site is the

presence of three, well-defined geological formations referred to as

Stone Complex 1, 2 and 3. These are tripartite layers of

cemented angular stones separated by sterile red clay (an in situsoil

formation, product of limestone weathering) found at 1.5 m, 10 m

and 15 m below datum, respectively. They are traditionally

interpreted as indications of a significant environmental instability,e.g., increased precipitation during a wet phase, affecting the

pedostratigraphy of the site.

Ksar Akil 1: EgbertIn 1938, Dohertys team discovered the skull and postcranial

remains of a juvenile Homo sapiensreferred to as Ksar Akil 1, andmore commonly known as Egbert [1415,30]. The remainswere found close to the rockshelter wall, 11.46 m below datum in

square F 3, in level XVII (or XVIII). These levels are associatedwith the Early Ahmarian, a classic Upper Palaeolithic industry in

the Levant. Egbert was covered by a pile of water-worn boulders,

which seem to indicate deliberate internment. An additional

maxilla and some rib fragments were found very close to the body,

indicating that a second individual may have been buried at the

same location. The fossils were poorly preserved and mostly

encased in breccia [30]. Only the skull was extracted and

reconstructed [31]. A metre above the burial(s), a break in the

geological and cultural sequence, a cemented formation referred

to as Stone Complex 2, separates the Early Ahmarian of levels

XXXVI from the subsequent later Upper Palaeolithic levels

XIIIVI [14,2122].The Egbert fossil is currently known only from descriptions,

photographs and reconstructed casts of the skull. Based on the

British Museum casts EM 274 and EM 275, Bergman andStringer [30] confirmed Ewings initial assessment [14,15] that

Egbert is an anatomically modern specimen belonging to a young

individual, possibly female, of about 79 years age at death [30].

The cranium is small and delicately built and there is no visible

supraorbital torus development. The zygomatic and maxillary

areas, as well as the vault and the mandible, reveal an

anatomically modern shape [30].

Ksar Akil 2: EthelrudaDuring the second field campaign at Ksar Akil, between 1947

and 1948, a partial maxilla was recovered from a levelstratigraphically deeper than Egbert. Ksar Akil 2 (referred to as

Ethelruda) was found in level XXV, three meters from the face of

the cliff, 15 m below datum. Level XXV was described as a red

clay, part of the lowest Stone Complex 3 and Ewing [32,33] noted

that the maxilla was definitely associated with an important

change in geology and lithic tradition, now understood to

represent the start of the IUP, the transitional industry of northern

Levant ([20]; see also Text S1 (SI Section I)). Interestingly, a singleatypical Emireh point from Ksar Akil, the fossile directeur for theindustry, was also discovered in level XXV. Ethelruda was thought

to be lost for many years, but the fossil has recently been located in

storage at the National Museum in Beirut (Directorate General of

Antiquities in Lebanon, Serial Number: 25724; see [34]).

The fossil consists of part of the right maxilla, and a small

portion of the left. It lacks all teeth, with the exception of the rightcanine root [32]. Ewing [32] attributed the specimen to a

Neandertaloid female adult on the basis of comparative metric

analysis with the fossils from Tabun I, Skhul IV and V, Gibraltar

and Chapelle-aux-Saints. This attribution however has been

questioned in recent years. According to Metni [35], the published

measurements of the maxilla fall within anatomically modern

ranges, which Ewing did not consider in his study. In addition,

Ewing reported that the Ethelruda fossil was morphologically

similar to Skhul V, which at the time was thought to be a

Neanderthal. Currently, Skhul V is considered to be an archaic

form of modern human [36], dating to between 11090 ka [37] or

Ksar Akil Chronology and Modern Human Expansion



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later [38]. Metni [35], Copeland and Yazbeck [34] and Yazbeck

[39] have suggested, therefore, that Ethelruda may be an

anatomically modern human. Further analytical work on the

fossil is planned (C. Stringer pers. comm.) and this will finalize the

taxonomic status of the fossil.

With the exception of about 10 teeth from the IUP and EarlyAhmarian levels of Ucagzl Cave in southern Turkey, most likely

belonging to Homo sapiens[4041], Egbert and Ethelruda are the

only other human fossils in the Near East directly linked to EUP

and IUP assemblages, respectively.

The lack of a firm chronostratigraphic framework for the Ksar

Akil sequence and the fact that neither the IUP nor the Early

Ahmarian levels of the site have been dated before, means that

great deal of uncertainty surrounds the age of the fossils and their

contexts. Their relationship, whether ancestral, contemporaneous

or descendant, to the Upper Palaeolithic European technocom-

plexes and to other EUP humans of Eurasia and Africa remainsunknown.

Materials and Dating Methods

Initial attempts to date bone material from Ksar Akil were

unsuccessful due to the complete absence of collagen (Text S1 (SISection II)). Both faunal remains, as well as modified bone objectsand tools, the latter sampled by our team in 2008 at the University

of Bordeaux (Inv. numbers: KA-73/9, KA-72/62, KA-74/59,

KA-72/43, KA-75/49, KA-74/26, KA-75/69, KA-72/42, KA-

72/55, KA-70/7273; with the permission of Prof. Fr. dErrico),

preserved no organics. Since no charcoal was available from Ksar

Akil, another type of material was required for dating purposes.

In the late Middle Palaeolithic, but mainly during the Upper

Palaeolithic periods, marine shell was regularly transported to the

site from about 610 km away for use as personal ornaments, tools

or for food [4244]. The molluscan collection from Ksar Akil is in

Figure 1. Stratigraphic and photographic documentation of the Ksar Akil excavations. (a) Stratigraphic sequence as established by theearly excavations of Boston College. The section drawing of the 23 m-deep stratigraphy illustrates both the archaeological levels (in Latin numerals)and the broad techno-typologically distinct phases (Mousterian, Initial Upper Palaeolithic, etc.) that these levels have been ascribed to; (b) Thediscovery of Egbert (Ksar Akil 1) in 1938. Close up of the skull in situ. Image copyright Pitt Rivers Museum, University of Oxford (accession number:1998.294.820); (c) Inferior view of the partial right maxilla of Ethelruda (Ksar Akil 2), modified after [32].doi:10.1371/journal.pone.0072931.g001




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fact one of the largest ever discovered at a Palaeolithic site. It

contains impressive numbers of both marine and terrestrial snails

(,2000 specimens), the vast majority of which carry evidence of

human modification such as perforation for suspension, burning,

polishing, snapping, and ochre residues.

Recent research into ways of addressing contamination when

dating shell carbonates [45] has led to the development of a new

pre-treatment and pre-screening protocol [46], which was used

here to date the Ksar Akil marine shells. This research [45] hasalso identified that the selection of aged gastropod shells was

very limited during the Upper Palaeolithic period, possibly due to

the poor quality of weathered marine shell for piercing and

manufacture into beads. We, therefore, consider the age of the

shell material used for beads to be closely related in the majority of

the cases to its selection and use by humans, as well as its

subsequent deposition at the site. No ornaments were found in

direct association with the human remains from Ksar Akil despite

the fact that large numbers of shell beads were discovered a few

centimetres above and below Egberts location, in levels XVII and

XVIII. Some of these beads were radiocarbon dated and are used

below to statistically constrain the age of the fossil.

Radiocarbon dating was performed at the Oxford Radiocarbon

Accelerator Unit (ORAU). The methods employed in dating shell

and charcoal material in the ORAU have been reviewed byDouka et al. [45,46] and Brock et al. [47], respectively. Overall,

we dated 26 shells from Ewings levels XXVIIIX obtaining 30

new AMS dates (Text S1 (SI Section II), Table S3). All dated

specimens were located at the Naturalis Natural History Museum

(Leiden, The Netherlands) and their inventory numbers are: RGM

550233, 550238, 550219, 550220, 550221, 550223, 550215,

550198, 550200, 550216, 550226, 550197, 550225, 550195,

550227, 550222, 550196, 550228, 550230, 550199, 550231,

550232, 550236. All necessary permits were obtained for the

described study, which complied with all relevant regulations.

Of the sampled material, twenty-one dated gastropod shells had

been transformed into beads, while five were of bivalves with

evidence of human manipulation (Fig. S2). The dated samples

were generally well preserved and no major mineral substitutionswere observed after thorough screening of the carbonate matrix

using X-Ray diffraction.

One charcoal sample from Tixiers excavations, dated in

Oxford in the late 1980s using a less-refined method (ABA), was

subjected to a harsher pre-cleaning protocol (ABOx-SC). This

protocol has been shown to provide more reliable results,

especially for old (.30 ka BP) charcoal [4849]. All radiocarbon

determinations were calibrated using the IntCal-Marine09 curve

[50] on the OxCal 4.1.7 software [51]. Bayesian statistical

methods were employed to analyse the results [51] (Text S1 (SISection III), Figs. S4S5). Comparisons to the NGRIP d18O record

[52] were used for broad climatic correlations.

Results

The new AMS dates on shell range from 39.5 ka BP for the late

Mousterian level XXVIII to ,3029 ka BP for level VIII (TextS1

(SI Section II), Table S3). An additional measurement on charcoal,

dated previously at the ORAU at 29.360.8 ka BP, was re-dated

after pre-treatment with a more rigorous protocol (ABOx-SC) at

30.260.17 ka BP. The new date is statistically identical, but has a

significantly higher measurement precision, and should be

considered more reliable.

Bayesian methods allow the formal incorporation, along with

the calibrated radiocarbon likelihoods, of all lines of evidence

pertaining to the chronostratigraphy of a site, such as breaks in the

sequence and the succession of archaeological levels. In the case of

Ksar Akil, two Bayesian models were built to account for the

degree of variation observed in the radiocarbon results, as well as

the uncertainties regarding the attribution of shell beads to

particular levels.

Initially, most of the old and all of the new determinations were

incorporated in a model structured around the individual levels

from which the dated samples derive. In the second model, the

individual levels were combined within five broad techno-typologically distinct phases and the results were grouped in

them; the assigned depth for each shell was not taken into account

since it only refers to the top of each level (often 12 m thick) and

not the actual position of the shell therein (for further model

specifications see Text S1, (SI Section III)). The second model is

more flexible and allows for a certain degree of material

movement through levels found in close proximity. It also

incorporates most available data with less statistical outliers. It

should be pointed out that the stratigraphy is defined in geological

layers that did not necessarily align with the archaeological levels

and their accompanying artifacts. In addition, several closely

associated levels (e.g. XVIIIXVIIXVI), often indistinguishable

in the field, are regarded as being developmentally very closely

related. Modelling these levels as a single Phase, therefore, does

not distort the archaeological association of the material.

Bayesian modelling outputThe output of the two models described above is very similar

(Fig. 2). Eleven outliers are identified in Model 1 (,28%, Fig. S4)

and 9 in Model 2 (,23%, Fig. S5). This is higher than expected

through statistical variation alone. One species of shell, Columbellarustica, gave consistently variable results and may be seriouslyaffected by post-excavation mixing (Text S1, SI Section III).Excluding determinations of this species, the number of outliers

in Model 2 drops to about 12%.

The age of the basal part of the Ksar Akil sequence is effectively

unknown and probably greater than 50 ka BP. According to the

modelling output (both iterations), the Mousterian terminates at

43.242.4 ka cal BP (68.2% confidence level) and is followed bythe IUP (Ksar Akil Phase 1 of Ohnuma and Bergman). No dates

exist for the lowermost IUP levels XXVXXIV; the phase appears

to be brief and lasts until about 41.640.9 ka cal BP (68.2%;

Model 2), or a millennium later based on Model 1, when the Early

Ahmarian begins. The largest difference in the modelling output

concerns the end of the Ahmarian and the start of the later Upper

Palaeolithic phases (Phases 36 of Williams and Bergman). In the

first scenario (Model 1), the end boundary of the Early Ahmarian

is estimated at ,40.139.5 ka cal BP, while in the second (Model

2) it is at 3937.5 ka cal BP (Fig. 2). Stratigraphically, the Early

Ahmarian is succeeded by sterile level XIV and Stone Complex 2.

Interestingly, the modelled span for the formation of Stone

Complex 2 coincides in both cases with the climate deterioration

during Heinrich Event 4, centred around 40 and 38 ka cal BP

(Fig. 2 and Figs. S4S5). This confirms the assessment of earlygeologists [19] that this geological formation represents a period of

significant climatic variability. Ksar Akil Phase 3 starts immedi-ately after, in Model 1 at 40.039.3 ka cal BP and in Model 2 at

38.134.6 ka cal BP (Fig. 2 and Figs. S4S5).

We used the Date function of OxCal to calculate a

probability distribution function (PDF) for the fossils likely age

within the modelled sequence. The determinations from the Early

Ahmarian layers XVII and XVIII, where Egbert was found, as

well as the determinations from above and below these layers

constrain the probable age of the specimen. In addition, the

modelled age for the beginning of Stone Complex 2 provides a




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terminus ante quemfor the deposition of the fossil. This PDF is based

on the assumption that Egbert was excavated in its original

location and is not intrusive from much higher levels. We believe

this to be true based on photographic documentation and other

lines of evidence. For example, there was no visible pit to suggest

downwards intrusion from a much higher level, and part of the

body was found protected by large water-worn and carefully

placed boulders, which may suggest that the child was buried at

about the same level as the occupation floor. The boulders

covering the body at the back of the rockshelter limited major

post-depositional disturbances, as did the presence of intact Stone

Complex 2 directly above the burial.

The same can be claimed for Ethelruda, discovered within the

middle clay layer of Stone Complex 3, and covered by a layer of

angular limestone flakes [32]. Ewing initially claimed that the

maxilla belonged to level XXIV, on the assumption that XXV was

sterile and a purely geological stratum [32]. In 1966 however, hepublished a corrigendum [33] where he acknowledges that

following Hooijers study [53], level XXV was not sterile, but

instead contained substantial amounts of faunal remains [33] as

well as evidence for hearths (D. Garrod photographic archive).

Consequently, the stratigraphic position of Ethelruda was

reinstated to level XXV [53]. In the Bayesian model, the

determinations from the uppermost Mousterian levels, as well as

the ones from the IUP were used to constrain the age of the fossil.

The calculated PDF for the age of Egbert corresponds to

40,85039,200 cal BP (68.2% prob.) or 41,05038,300 cal BP

(95.4% prob.) (Figs. 23). We have run more than 10 variations of

Bayesian models to assess the sensitivity of our modelled results. In

these, the priors were slightly changed, e.g., determinations were

grouped, un-grouped, moved across contexts or completely

excluded, and in all cases the particular PDF falls sharply between

4139 ka cal BP. Our conclusion is that the age estimate for

Egbert is robust.

For the oldest specimen, Ethelruda, the calculated PDF is earlier

and corresponds to 42,40041,750 cal BP (68.2% prob.) or

42,85041,550 cal BP (95.4% prob.). The results from both

models presented above are identical. In the case of Ethelruda, our

estimate is constrained by only a small number of determinations

above and below the fossil. We acknowledge that the addition of

further measurements may alter this estimate, possibly towards

earlier dates. For the moment, however, this is the most reliable

age estimate for this fossil.

Discussion

Comparison of the Ksar Akil specimens with directly andindirectly dated modern humans

In the past three decades, several AMH remains from across

Eurasia and Africa have been directly dated between 5030 ka

BP, although many of these determinations are potentially

problematic due to insufficient decontamination methods used in

the past. Only a small number of human bones have recently been

directly dated using up-to-date methodologies; these include the

skeletal remains from Kostenki 1 and Kostenki 14, Sungir 2 and 3,

Figure 2. Comparison of the start boundaries for each archaeological phase, produced by the two Bayesian models for Ksar Akil(shown in Text S1(SI Section III), Figs. S45). The boundaries, undated events, reflect the most likely age for the beginning of each of the majortechnocomplexes. Models are shown in different colours. The only area of significant discrepancy is the start boundary of the late Upper Palaeolithicphase (Phase 3), starting with layer XIII directly following Stone Complex 2. The start boundary for the Mousterian is very tentative, since there are nodeterminations from the lowermost part of the Mousterian phase. The boundaries and PDFs are compared to the NGRIP d18O record [52] and theGreenland Interstadials are numbered, as are the two relevant Heinrich Events 3 and 4.doi:10.1371/journal.pone.0072931.g002




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Figure 3. Comparison of the modelled ages (Probability Distribution Function; PDF) obtained for Egbert and Ethelruda with ageestimates of AMH from other Palaeolithic sites between 50,00030,000 years ago. The PDFs for the Ksar Akil fossils (Model 1 in green,Model 2 in black), as derived from the Bayesian modelling (Text S1 (SI Section III), Figs. S45), are plotted against the currently availabledeterminations for AMH from Europe and Africa [9,10]. The likelihoods for the directly-dated specimens are shown in dark grey, whereas the PDFs forthose dated indirectly, in light blue. Egbert is contemporaneous with the oldest directly-dated European modern human (Pestera cu Oase, [54]) andfalls within the earlier part of the ranges for both Nazlet Khater and Hofmeyer, the African AMH; these dates, however, are very imprecise. The Pesteracu Oase date is a mean of two determinations, one ultrafiltered and one not. The age estimate for Ethelruda is broadly similar to that for the AMHmaxilla from Kents Cavern, but not older than the AMH teeth from Cavallo in Italy. The radiocarbon determinations were calibrated with theINTCAL09/ Marine09 curve [50] and the modelling was performed using OxCal v.4.1.7 [51].doi:10.1371/journal.pone.0072931.g003




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Pokrovka, Pestera cu Oase and Pestera Muierii, Cioclovina, Buran

Kaya (partially) and Paviland (see references in [910]).

Important new evidence for the early presence of modern

humans in Europe has been generated in recent years through

indirect dating of human fossils using methods identical to those

employed here, namely Bayesian statistical modelling of chrono-

metric determinations and PDFs. A modern human maxillafragment (KC4) from Kents Cavern in Great Britain, associated

with only a very small number of chronologically non-diagnosticimplements, is placed between 44,20041,500 cal BP [10]. In

Italy, two deciduous molars from the transitional Uluzzian levels of

Grotta del Cavallo were ascribed to AMH, and not Neanderthals

as originally thought, and on the basis of direct radiocarbon dating

of shell beads from the same layers, the PDF for the most likely age

of the teeth was determined to be 45,00043,000 cal BP, and

possibly earlier [11]. Currently these are the oldest, indirectlydated, fossils in Europe.

Comparison of the PDF generated here for the Ksar Akil

specimens with the PDFs for the indirectly dated AMH fossils from

Cavallo and Kents Cavern, as well as with radiometric ages of the

directly dated European and African AMH, allows for an overall

assessment of their antiquity and inferred phylogenetic relation-

ships with these human fossils (Fig. 3). The PDFs for Cavallo and

Kents Cavern [10,11] clearly predate that of Egbert. Interestingly,the age estimate for Egbert overlaps significantly with the oldestdirectly-dated AMH fossil in Europe, the Pestera cu Oase

mandible from Romania [54] (Fig. 3). Unfortunately, the Pestera

cu Oase remains are devoid of an archaeological or cultural

affiliation. The age estimate for Egbert is in accordance with

current dating evidence for the appearance of the fully Upper

Palaeolithic technocomplexes in Europe [55,56], widely accepted

as the result of the establishment of AMH populations on the

continent.

Ethelruda is older and its age appears close to that of contexts

where Cavallo C and KC4 were recovered. It is worth noting that,

just as with the Ksar Akil specimen, Cavallo C also comes from a

transitional (Uluzzian) context.

The vast majority of the remaining directly dated modern

human remains (Fig. 3) are considerably younger. However, as

previously noted, only a few were dated with state-of-the-art

methodologies. Constant improvements in the methods used for

the dating of old and potentially contaminated samples, and their

application to such specimens (e.g. [57]), are needed if we are to

verify their age.

The Levant as a dispersal routeEgbert is clearly not associated with the onset of the Upper

Palaeolithic at Ksar Akil, but Ethelruda appears to be. The

determinations we have obtained from the site for the beginning of

the IUP at around 4142 ka cal BP correspond well with those of

other, recently-dated transitional industries in Europe, but they are

not older than these. This observation has potential implications

for the position of the Levant during the Middle to UpperPalaeolithic transition and in the process of the colonisation of

Europe by modern humans.

Despite increasing archaeological and genetic data in support of

an African origin for modern humans, there is little consensusabout the exact timing or about the route or routes taken during

migration(s) out of Africa and into Asia and Europe [58]. The

notion that modern humans dispersed first into the Near East and

then directly into Europe, is a common perception amongst

palaeoanthropologists and prehistorians. It is currently accepted

that modern humans migrated from Africa in several waves,

probably using a number of dispersal routes. Garcea [59]

distinguishes two Out of Africa movements by AMH, on the

basis of individual features and of being separated by a long time

span. The earlier wave or Out of Africa 2a took place between

about 130,000 and 80,000 years ago, while the second Out of

Africa 2b occurred at ,50,000 years ago, after an apparent gap

of about 30,000 years [59,60].

In the Levant, the archaic modern humans from Qafzeh and

Skhul, manufacturing Middle Palaeolithic tools and dating to

between 13080 ka BP [37] (but see [38]), form the basis of anearly exodus of modern humans through the region. Spatially

explicit modeling of the expansion of AMH allied with climate

reconstructions over the past 120 kyr [61] suggests that population

movement mainly occurred along the southern route, crossing into

the Arabian Peninsula at its most southerly point. Other research

supports this conclusion, (e.g. [62]). However, it is thought that this

early modern human genetic lineage became extinct, possibly at

the transition from MIS 5a to MIS 4 (,74,000 years ago) and did

not contribute to the much later AMH colonization of Europe

[63]. What occurs therefore tens of millennia after the early

expansion and the details of the second (re-)population of the

Levant by AMH, remains unclear and the archaeological record of

the region is at best sparse and difficult to interpret.

Following Qafzeh and Skull, all other fossils that have been

recovered in the Levant belong to Neanderthals until the time ofEthelruda and the likely-modern teeth from Ucagzl [40,41], to be

followed later by Egbert. The last two cases, and Ethelruda if

proved to be a modern human, may be seen as representatives of

the second wave of AMH human expansion in the region

(Garceas Out of Africa 2b). By then, fully anatomically and

behaviourally modern human groups appear to possess an Upper

Palaeolithic toolkit identified with the IUP and EUP technocom-

plexes.

Dating evidence from IUP and EUP sites in the wider Near

East, such as Ucagzl Cave in Turkey may be compared with our

new results from Ksar Akil. Based on the currently published dates

[40] and the output of Bayesian modelling, the IUP (layers IF) in

Ucagzl starts between 44.343.5 ka cal BP (68.2%) and the Early

Ahmarian (layers E (?)B) starts around 41.640.3 ka cal BP(68.2%). The IUP in Ucagzl seems to precede that of Ksar Akil

by 12 millennia, despite significant similarities between the lithic

assemblages. It should be remembered, however, that the

lowermost IUP levels (XXVXXIV) in Ksar Akil have not been

directly dated and there is a wide degree of chronological overlap

between the IUP at both sites. The Early Ahmarian is roughly

contemporaneous at both Ksar Akil and Ucagzl.

In Umm el Tlel (Syria), levels III2a and IIbase, described as

Paleolithique intermediaire, have been dated rather later, at

36.562.5 ka by TL on burnt flint, and at 34.560.89 ka BP with

AMS dating [64].

Much earlier dates, however, are often cited for the beginning of

the IUP in southern Levant, all from the open-air site of Boker

Tachtit [65]. There, basal level 1 is associated with four

conventional radiocarbon determinations on charcoal (SMU-580: 4728469048, SMU-259: 4693062420, SMU-184.45570,

GY-3642.34950 BP). These ages were produced almost 30 years

ago with old pre-treatment protocols and are very imprecise,

possibly reflecting the low amount of carbon in the dated samples,

an indication of possible sample heterogeneity. No effort has been

made to reproduce or add to these original dates from Boker

Tachtit, which have become central in the discussion of the early

arrival of AMH in the Levant.

Another set of early charcoal dates from Kebara Cave [13,66]

place the start of the EUP, specifically the Early Ahmarian Unit

IV, at ,4846 ka cal BP. Kebara is currently the only site where




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such early determinations have been obtained for a classic Upper

Palaeolithic assemblage. The site, unlike Ksar Akil and U cagzl,

lacks an IUP layer between the late Middle Palaeolithic Unit V

and the Early Ahmarian Unit IV, but instead an unconformity is

present at this interface. Complex site-formation processes and

erosion-induced sloping surfaces at the interface of these adjacent

stratigraphic units, as well as burrows and a large channel cutting

through the Middle Palaeolithic and Early Ahmarian units

[13,66], render the association of the dated charcoals with thearchaeology they are thought to date potentially problematic.

Some inconsistencies observed between charcoal determinations

produced with the routine (ABA) and more rigorous (ABOx-SC)

pretreatment methods [66] may be suggestive of: (i) complex

chemical processes affecting the samples and/or; (ii) charcoal

groups of different ages existing within adjacent units V and IV.

Rebollo et al. [66] state assuming that in the future such [early] dateswill be supported by samples from Ksar Akil, the Levantine IUP and EUP

assemblages herald the diffusion of UP technologies into Europe. Ksar Akilwith its long record of Upper Palaeolithic occupation, and

Ucagzl, have both yielded determinations that are considerably

younger, by at least 35 millennia, and do not support such a

simple unidirectional model of cultural and/or demic diffusion.

Clearly more work is needed to determine whether the Early

Ahmarian dates from Kebara, as well as those from the IUP layersof Boker Tachtit, are accurate and can be corroborated by data

from nearby sites.

The new chronometric results and Bayesian model from the

reference Palaeolithic site of Ksar Akil suggest that: (i) both the

IUP and the EUP of the northern Levant are roughly

contemporaneous with, and not older than, their corresponding

(transitional and Proto- or Early Aurignacian) technocomplexes in

Europe and; (ii) neither Ethelruda nor Egbert are ancestral to

European fossils associated with transitional and classic Upper

Palaeolithic contexts, respectively.

While the Levant appears an obvious route in and out of Africa

based solely on its geographical position, there is, as yet, no

evidence for significant human and animal migrations during the

Pleistocene ([67], and papers therein), let alone during the short

time window of the Middle to Upper Palaeolithic transition or

during the Out of Africa 2b scenario. The current evidence for

contemporaneity in the appearance of both transitional/IUP and

EUP technocomplexes in Europe and the Levant implies that the

northern Mediterranean Levantine coast might not be the point of

origin for the dispersal of the earliest Upper Palaeolithic outwards

and into Europe. This, in turn, suggests to us that current models

based on old assumptions regarding the pathway(s) of human

dispersal require further testing and, possibly, revision.

The makers of the IUPThe Levantine late Middle Palaeolithic is solely associated with

Neanderthals [68], and Ewings attribution of Ethelruda to a

Neandertaloid individual has helped shaping a generalized view

that Neanderthals may have been involved in the making of thetransitional/IUP layers, at least in its earliest phases (e.g. [5]). The

most recent archaeological and palaeoanthropological data from

Ksar Akil with regards Ethelruda (e.g. [35]), as well as the likely-

modern teeth from Ucagzl, where Mousterian levels have not

been identified, may provide a contrary view to traditional

assumptions on the authorship of the IUP by Neanderthals. Of

course, it is wise to remain cautious on the taxonomic status of

both Ethelruda and the teeth from Ucagzl until more detailed

scientific work has been undertaken using state-of the-art

methodologies. Further work is also urgently required to address

whether other technocomplexes exhibiting similar characteristics,

such as the Balkan Bachokirian (e.g. level 11 of the eponymous

site, containing fossil remains; [69]) or the Bohunician (or Emiro-

Bohunician; [70]) of Central Europe, fall into the same category.

Supporting Information

Figure S1 Location of the Ksar Akil site, Lebanon, a fewkms NE of Beirut.

(TIF)

Figure S2 Examples of the dated shell specimens fromKsar Akil. The vast majority consists of beads of Nassariusgibbosulus/ circumcinctus while KA 30 is an example ofColumbellarusticashell. KA 54, an Ostreasp. shell, is one of the very few shellscoming from Middle Palaeolithic layers.

(TIF)

Figure S3 Plot of all available dates from square E4.OxA-20491 and OxA-25656 come from adjacent square (F5) and

are used here as a terminus post quem. The determinations areplotted here together in order to check the chronological variation

among specimens deriving from the same excavation square. The

dates are consistent with the stratigraphic position. Assuming

constant sedimentation (an over-simplified scenario), we may

calculate an accumulation rate of 0.88 m of sediment deposited atthe site every 1000 years.

(TIF)

Figure S4 Bayesian Model 1. Initial Bayesian plot with allnew dates, as well as previously obtained ones from the Tixier

excavations. The model is structured around individual layers and

phases. Of the 39 determinations, 11 are flagged as outliers.

(TIFF)

Figure S5 Bayesian Model 2. Second modeling iterationcontaining most available dates from the Early Upper and Middle

Palaeolithic levels of the site, including previously obtained dates.

Here, individual layers are grouped together within broad

industrial phases (see text for details). Of the 39 determinations,

9 outliers are identified.

(TIFF)

Table S1 Archeological correlation of the Ksar Akilsequence, Boston College excavations (19371938, 19471948) and Tixier excavations (19691975).

(DOC)

Table S2 Previous chronometric determinations fromKsar Akil. The majority of the dates relate to the late UpperPalaeolithic layers and were obtained on material from Tixiers

excavation.

(DOC)

Table S3 New radiocarbon determinations from KsarAkil and details for stratigraphic details for eachsample. KA 51 was dated twice as it underwent mineralogical

separation (see [32]) due to the presence of calcite in the originalfraction. In the last column the percentage of secondary calcite in

the shell matrix, established by XRD analysis, is indicated. The

differentiation between Nassarius gibbosulusor Nassarius circumcinctuswas not always possible due to the preservation state of the shells;

here they are all tentatively ascribed to the former species. The

d13C value is also given when this was unusual for marine shells,

therefore indicating either some degree of meteoric diagenesis or

other technical issues. The 3 determinations marked with an

asterisk were not used in the modeling since they are most

certainly problematic (see text).

(DOC)




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Text S1.

(DOC)

Acknowledgments

We would like to thank the staff of the Oxford Radiocarbon Accelerator

Unit (ORAU) at the University of Oxford for the support throughout this

project. Chris Stringer and Corine Yazbeck are kindly thanked for

information on the current work on the Ksar Akil fossil specimens. The Pitt

Rivers Museum, University of Oxford, and Christopher Morton, are

thanked for providing an archival picture from the early excavations in

Ksar Akil.

Author Contributions

Conceived and designed the experiments: KD REMH TFGH. Performed

the experiments: KD. Analyzed the data: KD CAB TFGH . Contributed

reagents/materials/analysis tools: FPW. Wrote the paper: KD CAB

TFGH.

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SUPPORTING INFORMATION

Section I: The site of Ksar Akil and further details of the archaeological

sequence

Section II: Radiocarbon dating

Section III: Bayesian-based chronological framework

References


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"

Section I:

Ksar Akil: The site and archaeological sequence

a. Location and history of research

The Ksar Akil rockshelter (other spellings include: Ksar 'Akil, Ksr 'Akil, Ksar 'Aqil) is

located 10 km northeast of Beirut (Fig. S1), just above the coastal plain in the foothills of the

Lebanon Mountain range. The site is situated at the base of a high limestone cliff on the

north bank of the Antelias River valley.

The investigations at Ksar Akil have now spanned nearly 90 years, beginning somewhat

inauspiciously when the owner of the land probed the site for treasure in 1922 and dug

through 15 meters of deposits. It was not until 1937 that the first large-scale and scientific

excavations began on the advice of the Abb Henri Breuil [1]. The archaeological team

came from Boston College, Massachusetts and was directed by Joseph G. Doherty, S.J. [2,

3]. Doherty, a student of Dorothy Garrod at Cambridge University, was assisted by J.

Franklin Ewing, S.J., of Fordham University who joined the team as paleontologist and

anthropologist in June 1938 [2, 3]. Ewing assumed the directorship of the project for the

1947-1948 field seasons, suggesting these early investigations by the Jesuit priests actually

represent the efforts of both Boston College and Fordham University.

An extensive series of photographs illustrating the 1937-1938 excavations was published by

Bergman [4, 5], using images supplied to Garrod by Doherty [6]. Some of these have now

become publicly available through the Pitt Rivers Museum, University of Oxford, after the

recent digitization of D. Garrods photographic archive (http://web.prm.ox.ac.uk/garrod/).

Based on the surviving documentation, it is apparent that the field methodology does not

measure up to modern standards, although for the time it was relatively rigorous.

The excavation grid was mapped out in 16 two-meter squares, with alphabetic letters

designating the east-west axis, and numbers designating the north-south axis [3, 5]. Shovel

skimming was the primary means of excavation [5] along with troweling of wall sections,

while delicate objects were examined with brush and trowel [5]. Sediments were sieved

through a medium mesh and the artefacts boxed or bagged by provenience unit [5]. Since

most specimens were heavily encrusted with breccia, each artefact was brushed, scraped and

washed [1]. It is estimated that perhaps as many as 2,000,000 lithic artifacts, bone and antler

tools, elements of personal ornamentation, such as shell beads, as well as faunal remains

were recovered in the two field seasons.


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"

Doherty, guided by the profile visible in the 1920s-era treasure-hunters pit, used geological

layers to define the stratigraphy. These were often of substantial size, often with a thickness

of between 1 and 2 meters, and did not necessarily align with the archaeological levels [7,

8]. These excavations reached 23 meters below datum, and revealed 36 levels, I-XXXVI,

from top to bottom (Fig. 1, Main Text).

In the subsequent 1947-1948 field seasons, Ewing developed a more refined stratigraphy

and concentrated on collecting a greater variety of artifacts, specifically the miniscule

bladelets common in the upper portions of the Ksar Akil sequence [8, 9]. For the later

Upper Palaeolithic levels, this resulted in Dohertys original stratigraphy involving only

eight levels (XIII-VI) being subdivided into 27 levels [8].

In 1969, Tixier began a series of investigations at Ksar Akil [7, 10, 11]. Using careful

excavation techniques, such as the three-dimensional recording of artifacts, he established a

finely divided stratigraphy and recognized a series of sols dhabitat near the shelter wall.

During the course of work that ended prematurely in 1975, Tixier reached a depth of nearly

9 meters and identified 30 different levels. His vastly refined stratigraphy is evidenced by

the fact that he identified 12 discrete levels within the equivalent elevations of Level VIII

from the 1937-1938 investigations. Based upon the published sections from the Boston

College and the 1969-1975 excavations, it would appear that the deepest level excavated by

Tixier between 1969 and 1975 is equivalent to levels X-IX of the 1937-1938 investigations,

or levels XI-Xc of the 1947-1948 season [5, 8].

Overall it is estimated that about 700 m3 of deposit have been removed from the site.

According to the geological observations of Wright [12, 13], there is strong evidence that

climatic variability affects soil formation and occupation patterns. The three Stone

Complexes may be indicative of this.

The actual processes responsible for the formation of the Stone Complexes have been seen

as the result of the effect of pluvial glaciation on the weakening of limestone surfaces

[12]. Ewing himself and other subsequent researchers supported that the intercalated red

clay deposit represents disintegrated and decalcified limestone that separates stony levels

above and below, the latter coming from the overhanging roof of the shelter and therefore

very likely being the result of varying conditions of humidity (and seasonal variations of

temperature) [12]. Azoury [1], on the other hand, suggests that since there is alluvial sand

and pebbles in the deposits below a depth of 16 m (in the MP levels just below Stone

Complex 3), the red clay deposit may have been introduced by the stream rather than having

been developed in situ by soil weathering process. In our opinion, both explanations remain


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"

tentative and need to be substantiated by further in situ observations and modern analytical

techniques.

b. Archaeological Sequence

Middle Palaeolithic :1937-1938 Season, XXXVI-XXVI

The first Middle Palaeolithic occupation, from level XXXVI to level XXVI (19.415 m

below datum, respectively), took place while the rockshelter was intermittently flooded by

the nearby stream [12]. The alluvial deposits stop between -17 m and -16 m when the course

of the stream changed and habitation of the rockshelter became more stable and dense [14].

Copeland [5] assigned the assemblage to Phase 3/ Layer B (and possibly Phase 2/ Layer C)

Tabun Mousterian, while Marks and Volkman [15] assigned the lower levels (XXVIIIB and

XXVIIIA) to Phase 1/ Tabun D Mousterian based on the presence of ovoid blanks, Levallois

and discoid cores, and Mousterian tool types, while the uppermost levels (XXVIIB to

XXVIA) were assigned to Phase 2/ Layer C type Mousterian due to the presence of blade

and point forms.

Initial Upper Palaeolithic: 1937-1938 Season, XXV-XXI / Ksar Akil Phase 1

The earliest Upper Palaeolithic occupations at Ksar Akil, levels XXV-XXI, have been

regarded as part of the transition from the Middle to Upper Palaeolithic [16, 17]. It should

be noted that many authors have used the term Transitional to describe similar industries,

while recognizing the Upper Palaeolithic character of both the technological operating

chains and tool typology [18, 19]. We agree with recent characterization of these

assemblage types as Initial Upper Palaeolithic (IUP) by scholars [20]. A possible

occupational hiatus in levels XXV-XXIV, identified as Stone Complex 3, possibly

indicates abandonment of the site and separates the latest Mousterian and first Initial Upper

Palaeolithic levels.

There seem to be two distinct stages represented in the Initial Upper Palaeolithic layers,

which collectively are referred to as Upper Palaeolithic Phase I by Ohnuma and Bergman

[17]. The sample from levels XXV-XXIV is small, but characterized by opposed platform

cores with parallel sides. Levels XXIII-XXI, on the other hand, contained numerous single

platform blade cores with faceted platforms and converging sides. The triangular shape of

the cores cause blade removals to converge, resulting in the production of blanks

morphologically similar to elongated Levallois points. The blow used to detach the blades in


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these levels is well on to the striking platform (non-marginal flaking), resulting in relatively

thick blanks with large butts. An analysis of the ventral surfaces of the blanks in these levels

suggests that most blades were detached with soft hammers [17].

The assemblages in levels XXV-XXI are almost entirely composed of Upper Palaeolithic

tool types including varying percentages of chamfered pieces. This artifact type, generally

rare in the rest of the Levant, is made by a tranchet blow at the proximal or distal end of a

flake or blade [21]. Other components of the tool kits include end-scrapers and truncation

burins, which are always more numerous than the dihedral types [6]. Outside of the

Lebanese sites situated along the coastal plain, such as Abu Halka in northern Lebanon,

good comparative material for the Initial Upper Palaeolithic at Ksar Akil has been found at

agizli cave, southern Turkey [19, 22].

Early Ahmarian: 1937-1938 Season, XX-XVI / Ksar Akil Phase 2

Although no clear-cut technological distinction exists between level XX and those

immediately preceding it, there is a shift from cores with single, faceted platforms and

converging sides to parallel-sided cores with opposed, plain platforms [17]. Cresting and the

core tablet technique begin to be used more often for preparation and maintenance. The

blade blanks tend to be much thinner than in levels XXV-XXI and are produced by striking

quite close (marginal flaking) to the edge of the core platform, resulting in tiny butts. In

order to avoid damaging the platform, abrasion is used extensively to remove overhang and

thicken and strengthen the edge. The blades in these levels are believed to have been

detached with soft hammers, probably by direct percussion.

Levels XX-XVI, Ksar Akil Phase 2, have tool assemblages consisting of end-scrapers and

retouched blades and bladelets including backed and partially backed blades, as well as

robust el-Wad points (over 15% of the tool kits) and pointes face plane. Thepointe face

planeat Ksar Akil [4, 6] is a leaf-shaped piece formed by invasive retouch, which has also

been recognized in a remarkably similar Early Ahmarian assemblage at agizli Cave by

Kuhn et al. [19, 22]. A curious feature of all these levels is the relative scarcity of burins;

the burin index for levels XVIII-XVI ranges between 1 and 1.5 [6]. It is widely agreed that

Phase 2 fits the description of the Leptolithic lineage, Ahmarian industry, and has recently

been described as its northern facies [8, 17, 18, 23].

Stratigraphic Hiatus: 1937-1938 Season, XV and XIV


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Above level XVI is level XV, part of Stone Complex 2, while the following level XIV

represents a major break in the occupation of the site [6]. Both were quasi-sterile. Herbert

Wright [13] indicated that at about 10.5 meters below datum there was a distinct layer of

red clay about 30 cm thick overlain by a layer of angular stones of equal thickness. The red

clay has the appearance of the typical terra rosa developed on the limestone in the Jurassic

bedrock [and]is considered to be a soil developed in situ in the rock shelter. The exact

palaeoclimatic significance of Stone Complex 2 was difficult for Wright to interpret, but he

felt that it may represent an episode of intensive weathering, such as during a pluvial phase,

coinciding with a period when the rockshelter was not occupied allowing for development of

the soil. Regardless of the mechanisms of formation, Stone Complex 2 coincides with a

break in the cultural sequence that separates the Early Ahmarian industries of levels XX-

XVI from the later Upper Palaeolithic levels, XIII-VI [4].

Later Upper Palaeolithic :1937-1938 Season, XIII-VI; 1947-1498 Season, XII VI a and b /

Ksar Akil Phases 3-6

The upper portion of the Ksar Akil sequence, comprising levels XIII-VI of the 1937-1938

field seasons and levels XII-VIa and b of the 1947-1948 field season, spans approximately

7.25 meters of deposits from 10.65 meters to about 3.40 meters below datum. Currently the

descriptor Aurignacian has been removed from these layers and researchers (e.g. [8])

prefer the phase designations as summarised in Table S1.

This upper portion of the sequence is stratigraphically and culturally complex (Table S1).

While the Early Ahmarians at Ksar Akil successfully produced the full range of blanks

required for tools within the framework of blade core reduction (e.g., flakes, core tablets,

blades and bladelets), this is seemingly not the case for later Upper Palaeolithic people at the

site. Specifically, each of the levels incorporated into Phases 3-6 is characterized by

multiple operating chains for the production of blades and/or bladelets with twisted profiles,

as well as straight or curved profiles. These involve objects clearly intended for use as

cores, as well as multifaceted burins and a variety of scrapers such as the carinated and thick

nosed and shouldered types, all of which occur in varying frequencies in levels XIII-VI. As

suggested by the work of Chiotti [24] and Hays and Lucas [25], carinated and multifaceted

burins and nosed and shouldered scrapers appear to be multipurpose, serving as both cores

and tools.

There have been considerable problems aligning the upper part of the Ksar Akil sequence

with the rest of the Levant with the notable exception of levels VIII and VII (Phase 5) and


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level VI (Phase 6). These are widely considered to represent the Levantine Aurignacian,

sensu stricto, and the Atlitian, respectively. Whether the blade and bladelet dominated

industries of Phase 3 (Levels XIII-XI) and Phase 4 (Levels X and IX) represent

developmentally earlier stages of the Aurignacian, as posited by Tixier and Inizan [7, 26],

still remains a matter of debate.


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BOSTON COLLEGE EXCAVATIONS TIXIER EXCAVATIONS

Ksar Akil

Phases

(Boston

College

Excavations)

1937-1938

Field

Season

Levels

1947-1948

Field

Season

Levels

Assemblage Characteristics

Ksar Akil

Phases

(Tixier

Excavations)

1969-1975

Excavation

Levels

Outils Caracteristiques

7 Not studied VIb, VIa

Multiple reduction strategies

including typical

blade/bladelet manufacture

and twisted bladelet

manufacture from lateral

carinated pieces; numerousretouched bladelets; burins

and scrapers present in nearlyequal numbers.

IIICouche7

8a

Numerous retouched

bladelets, scrapers and

burins; burins typically flat-

faced and multifaceted, and

burins on truncation arelarger; end-scrapers on

unretouched blades

6 VI

IXa, VIIIc,

VIIIb,VIIIa,

VIIh, VIIg,

VIIf, VIIe,VIId, VIIc,

VIIb, VIIa

Multiple reduction strategies,

twisted bladelet manufacturewith lateral carination and

twisted bladelet cores,

elevated burin index, burinson concave truncation,

Dufour bladelets

IVCouche

8ac-10a

Truncation burins on small,

thick flakes


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Ksar Akil

Phases

(Boston

College

Excavations)

1937-1938

Field

Season

Levels

1947-1948

Field

Season

Levels


Ksar Akil

Phases

(Tixier

Excavations)

1969-1975

Excavation

Levels


Not

identified

Notidentified

IXb, IXa,VIIIc,VIIIb,

VIIIa


twisted bladelet manufacture

with lateral carination andtwisted bladelet cores,

elevated burin index, burins

on concave truncation,

Dufour bladelets

VCouche10b-10g

Flat-faced multifaceted

burins (i.e.

Laterallycarinated pieces) and sharprise in bladelets with semi-

abrupt, alternate retouch (i.e.Dufour bladelets)

5VIII and

VII

Xb, Xa,

IXf, IXe,

IXd, IXc

Multiple reduction strategies,flake production,

predominantly blades andbladelets with straight or

curved profiles, but twisted

dbitage also frequent,

elevated scraper index,nosed and shouldered

scrapers, tiny retouchedbladelets, bone and antler

tools

VICouche

10h-11bc

Nosed, shouldered and

carinated scrapers, various

side-scraper types, decline in

retouched bladelets, althoughstill abundant

4 X and IXXIb, XIa,

Xc


blades and bladelets with

straight and curved profiles,

reduction in twisted dbitage,elevated scraper index,

VII Couche 12

El-Wad points, simple end-

scrapers, nosed and

shouldered scrapers, rare

Aurignacian blades, and fewburins


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Ksar Akil

Phases

(Boston

College

Excavations)

1937-1938

Field

Season

Levels

1947-1948

Field

Season

Levels


Ksar Akil

Phases

(Tixier

Excavations)

1969-1975

Excavation

Levels


retouched bladelets, el-Wad

points and variants

3 XIII-XI XII


twisted blades and bladelets,

elevated burin index, flat-faced carinated burins, lateral

carinated scrapers and burins,twisted el-Wad points

Notexcavated


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"

Section II:

Radiocarbon dating

a. Previous chronology for Ksar Akil

Prior to this work there were 26 radiometric dates from the site, from the later Upper

Palaeolithic and the Middle Palaeolithic layers but none from the IUP or Early Ahmarian

ones (SI Table S2). These dates were produced in three radiocarbon facilities (Oxford,

Groningen and Monaco) and the vast majority relate to Tixiers excavations [26]. No

radiocarbon dates existed for material from the older excavations although two radiocarbon

determinations (GrN-2579 and GrN-2195) were made on clay and shell samples,

respectively, collected in 1959 from Ewings 1948 open sections [27]. A date (Gro-

2574/75) is mentioned by Ewing but no other record exists for it; it is very likely that this is

the same date as GrN-2579. Finally, four U-series dates on two Mousterian bones from the

bottom of the sequence were produced by van der Plicht et al. [28], but the results were

inconclusive.

During the late 1980s, a series of bones from Ewings excavations submitted to Oxford for

AMS radiocarbon dating but failed to produce any collagen. Similarly, in 2008, we sampled

10 bone points recovered by Tixier and curated at the University of Bordeaux I. We

analysed the points for their N content and calculated the C:N atomic ratios, both used as a

proxy for collagen presence and state of preservation. Again no collagen was identified in

any of the sampled implements and the analytical values ranged much beyond accepted

levels (%N=0.2-0.21 and C:N=20-91; where accepted values are %N=>0.75-1 and

C:N=


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Table S2 Previous determinations from Ksar Akil. The majority of the dates relate

to the late Upper Palaeolithic layers and were obtained on material from Tixiers

excavation.

Lab. code C Level/ depth Material Excavator

OxA-1791 23170 400 3 upper Charcoal Tixier

OxA-1792 22850 400 3b major Charcoal Tixier

OxA-1793 22050 360 3b lower Charcoal Tixier

OxA-1794 22480 380 3bb Charcoal Tixier

OxA-1795 22850 380 3c Charcoal Tixier

OxA-1796 21100 500 7bb Charcoal Tixier

OxA-1797 26900 600 8a Charcoal Tixier

OxA-1798 29300 800 8ac Charcoal Tixier

OxA-1803 30250 850 9a Charcoal Tixier

OxA-1804 31200 1300 10 lower Charcoal Tixier

OxA-1805 32400 1100 11bm Charcoal Tixier

MC-1191 26500 900 8ai Charcoal Tixier

MC-1192 32000 1500 12.0 m Charcoal Tixier

MC-410 24400 900 3b/ 2.80-2.90 m Landsnail Tixier

MC-411 14100 500 C/ 3.50-3.55 m Bone Tixier

MC-? 28600 680 Phase V n/a Tixier

MC-686-88 27000 Phase V n/a Tixier

MC-679 27350 Phase VI Charcoal Tixier

MC-574-

580

? ? Dates not

published

Shell? Tixier

GrN-2195 28840 380 6-7.5 m Shells Ewing, 1948open section

GrN-2579 43750 1500 XXVI orXXVII/ 16 m

Clay treated ascharred matter

Ewing, 1948open section

Gro-

2574/75

44400 1200 XXVII/ 16 m

Red clay

beneath StoneComplex 3

Clay Ewing, 1948

open section.

Same asabove ?

G-88174 47000 9000 XXVI BE V U-series/ bonesurface

1947-8?

G-88173 19000 5000 XXVI BE V U-series/ bone

bulk

1947-8?

G-88177 51000 4000 XXXII FV U-series/ bone

surface

1947-8?

G-88178 49000 5000 XXXII FV U-series/ bone

bulk

1947-8?


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"

b. New radiocarbon chronology

Materials for dating

The Upper Palaeolithic molluscan collection of Ksar Akil contains impressive numbers of

both marine and terrestrial landsnails. The shells from the early excavations, about 2000

specimens, were studied initially by Altena Van Regteren [31] at the Rijksmuseum van

Natuurlijke Historie in the Netherlands, where the material was sent by Ewing himself.

Inizan and Gaillard [32] studied about 200 shells from Tixiers recent excavations, from the

upper stratigraphic levels. Forty-five molluscan species were identified; Nassarius

gibbosulus, Columbella rustica, Osillinus turbinatus and Glycymeris sp. are the most

abundant throughout the sequence. Ewing [33] mentions thousands of shells of the terrestrial

snailHelixsp., as well as marine shells ofPatellasp. and Trochussp., from 13 m. (~XIX)

upwards. These are not accounted for in the aforementioned studies nor are currently present

in such numbers in the surviving collection. It is possible that only a portion of the

invertebrate remains made their way out of Lebanon. An interesting comparison of the

molluscan assemblage from Ksar Akil with that of a!zl, in the northern Levant, was

reported by Kuhn et al. [34].

In 2007, the material studied by Altena Van Regteren (31) and lost since, was located by

us at the Naturalis Natural History Museum (Leiden, The Netherlands). The shells appear to

derive from both 1937-38 and 1947-48 excavations, since, according to Hooijer [35],

material from the former campaign is only accompanied by depth (3-15.4 m) and square

information (E5, F3, F5), while material from the latter season has been ascribed level

information too.

We favoured samples with the best possible recording and with the best preservation state.

We selected 54 shells from levels VXVIII, of which 26 were dated (Fig. S2). Most of these

are beads on gastropods, either Nassarius gibbosulus or Columbella rustica, but a few

bivalves (Glycymeris and Acanthocardia sp.) were also dated to check inter-species age

differences and to elucidate modes of exploitation. Many shells preserved original

pigmentation, while some had ochre residues on them (e.g. KA 31 and KA 51, Fig. S2). A

Glycymeris bimaculata(KA 9) bore traces of deliberate edge modification, possibly for use

as a scraper [36].

The pretreatment methods used to date the samples in Oxford were briefly described in the

main text, as well as in recent publications [30, 37].


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"#

Results

Overall, 30 new radiocarbon dates were produced: 29 on shell (KA 51 was dated twice and

KA 54 thrice) and one on charcoal. The new determinations are shown in Table S3 along

with the calibrated ranges obtained using the latest calibration curve, IntCal09 for the

terrestrial charcoal sample and IntCal09-Marine for the shells [38]. A constant marine

reservoir of 400 14C years is included in the marine curve and, in addition, we corrected the

shell measurements for the Mediterranean local reservoir (!R=58 8514C years; [39]).

The lowermost stratigraphic unit for which four dates were obtained, is the Mousterian level

XXVIII, at 16.6 m below datum, just below Stone Complex 3. An Ostrea sp. valve was

dated three times due to problems identified with the carbonate mineral, and produced three

different results (OxA-X-2344-23: 35900 400; OxA-X-2361-17: 33810 180; OxA-

20491: 39310 330 BP). The "13C values for the first two, which are also the youngest,

ranged from -2.6 to -3.8. This suggests some degree of meteoric diagenesis and

incorporation of terrestrial carbon compounds. Unfortunately, shells of Ostrea sp. are

predominantly calcitic in nature and XRD screening cannot help discriminate secondary,

post-depositional mineral formation, such as low-Mg calcite. OxA-20491, the third date,

was produced on a sample taken from a different part of the valve (away from surface layers

sampled before and closer to the thicker umbo area) and this is the oldest determination.

This is considered the most reliable of the three and its "13C value falls within the expected

range for marine carbonates (1.6). In order to determine securely the age of layer XXVIII,

we obtained a second Ostrea sp. valve,

douka_etal_2013_chronology of ksar akil-plos one with si

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