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Pleistocene Exchange Networks as Evidence for theEvolution of Language

duction sequences. The model focuses on the relation-ship between hominid communication systems andthe ability of hominid groups to exploit resources. Us-ing raw-material movement data as a parallel inquiryinto the emergence of modern human abilities suchas language it is possible to refine and strengthen theargument for the emergence of modern human be-haviours in Africa sometime before 100,000 years ago.

Distances of raw-material transfer are comparedfrom African and European sites between 2.5 mil-lion to 20,000 years ago. An ‘occurrence’ of a raw-material transfer is defined by one or more associatedartefacts made from a raw material that can besourced to a specific location. For example, one oc-currence can be a single chert artefact that is sourcedto an outcrop 5 km away, or several hundred piecesof obsidian in the same stratigraphic context that canbe sourced to an outcrop 40 km away. I define lan-guage as communication that involves syntax, use ofarbitrary bi-directional symbols and expression ofdisplacement (Aiello 1998, 23). Syntax is the hierar-chical structuring of words or phrases within sen-tences so that relationships between multiple subjects

Ben Marwick

Distances of raw-material transportation reflect how hominid groups gather and ex-change information. Early hominids moved raw materials short distances, suggesting a home-range size, social complexity and communication system similar to primates in equivalentenvironments. After about 1.0 million years ago there was a large increase in raw-materialtransfer distances, possibly a result of the emergence of the ability to pool information byusing a protolanguage. Another increase in raw-material transfer occurred during thelate Middle Stone Age in Africa (after about 130,000 years ago), suggesting the operationof exchange networks. Exchange networks require a communication system with syntax, theuse of symbols in social contexts and the ability to express displacement, which are the featuresof human language. Taking the Neanderthals as a case study, biological evidence and theresults of computer simulations of the evolution of language, I argue for a gradual rather thancatastrophic emergence of language coinciding with the first evidence of exchange networks.

Recent work by archaeologists has focused on howthe first evidence of modern human behaviours suchas symbol use may be evidence for language (Noble& Davidson 1996; Mithen 1996). While the pursuit ofsymbolic behaviours in the archaeological recordleads to mostly robust claims about language emer-gence, they risk producing a rather coarse-grainedscenario. Renfrew’s (1996) Sapient Behaviour Para-dox suggests that while a group may be capable of acertain level of cognitive ability, individuals maynever manifest those abilities in a way that will bedirectly recognizable by archaeologists. As a conse-quence, the dated evidence for ‘sapient’ behaviourmay be much more recent than the first appearanceof this behaviour.

The aim of this article is to present a model forthe evolution of language using distances of raw-material transfer. The model is based on Whallon’s(1989) suggestion that language and alliance net-works co-evolved during the Upper Palaeolithic. Thisprovides an alternative to those models focusing ontraditional evidence of modern human behavioursuch as symbolic artefacts and complex artefact re-

Cambridge Archaeological Journal 13:1, 67–81 © 2003 McDonald Institute for Archaeological Research

DOI: 10.1017/S0959774303000040 Printed in the United Kingdom

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(Semaw 2000). There are 14 hominid sites with stoneartefacts in equatorial Africa dating between 2.5 and1.9 million years ago (Feblot-Augustins 1997, inven-tories 1 & 2). The distances of raw-material transferat these sites are either not documented or less thanone kilometre.

After 1.9 million years ago the first Homo habilisfossils appear in the East African rift valley (Klein1999). The most significant distinguishing feature ofHomo habilis is an increase in relative and absolutebrain volume (Elton et al. 2001). Also dating to about1.9 million years ago are the oldest examples of raw-material transfers greater than 1 km. During the pe-riod 1.9–1.6 million years ago there are data on 26instances of raw-material transfers from 12 sites orlayers at Olduvai Gorge (Tanzania) and Koobi Fora(Kenya) (Feblot-Augustins 1997, inventory 3–4). Mostof these transfers were over a distance of three kilo-metres or less, with a small number of transfers atgreater distances to a maximum of 13 km (Fig. 1).Over 95 per cent of artefacts are made on stone col-lected from a distance of 3 km or less (Feblot-Augustins 1997, inventory 4).

The 13 km distance is a reasonable approxima-tion for the minimum home-range radius of latePliocene hominids. Individual late Pliocene homi-nids were probably able to procure raw materialdirectly from 13 km as part of their ranging activity.Whether the hominids moved the raw material inone trip or in a series of small transports is not acrucial point. The significant detail is that the latePliocene hominids had the cognitive capacity to ac-quire raw material and hold on to it until they were13 km from the source. Steele (1996) has predictedhominid home-range sizes from regression equationsinvolving measurements of adult body mass, brainvolume, group size and home-range diameter. For alocal group of 25 Homo habilis individuals, Steele(1996, 249) predicts a maximum home-range radiusof 13 km. This independently confirms the reliabilityof raw-material transfer distance as an indicator ofhome-range size for late Pliocene hominids.

Primate home range and object transfer data

The suggested home-range size for late Pliocenehominids, is similar to the home-range radius ofprimates in equivalent environments. Chimpanzeesat Mt Assirik (Senegal) occupy an arid environmentthat is a patchwork of riverine forest, open and closedwoodland, scrub and dry and wet grassland(McGrew et al. 1981). Pollen, faunal and sedimenta-tion data suggest that Plio-Pleistocene East Africa

Figure 1. Transfer distances of raw materials (n = 26) at12 African sites or layers, 1.9–1.6 Ma.

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and objects can be expressed. Arbitrary bi-directionalsymbols are things (in the context of language thisrefers to expressions such as utterances and ges-tures) that represent other things without resem-bling those things (non-iconic) or pointing to them(non-indexical). The expression of displacement isthe ability to refer to actions, objects and ideas be-yond the immediate context or beyond the ‘here-and-now’. Protolanguage is harder to define, but probablyincluded basic symbolic reference to perceived phe-nomena and the ability to communicate about themin simple topic-comment strings. Protolanguage neednot have syntax, the ability to express displacementor regular context-free symbol use. I argue here thatprotolanguage possessed long-term stability but lim-ited expressive power and that extensive use of sym-bols was not common amongst protolanguagespeakers.

The model proposes that the distances of raw-material transfers for late Pliocene hominids 2.5–1.9million years ago suggest they used primate com-munication, status-based negotiation, and had someplanning ability. Raw-material transfer distances fornon-modern hominids 1.9–0.2 million years ago showan increase at about 1.0 million years ago, indicatingthe emergence of a protolanguage, the ability to ne-gotiate face-to-face and to pool information in a localgroup. The emergence of the protolanguage mayhave been selected for by a climatic change towardsincreased aridity. For modern humans, languageabilities become visible after 130,000 years ago inAfrica, and after 100,000 years ago in Europe. Usingthe Neanderthals as a case study, and evidence fromcomputer simulations, I show that language evolu-tion was a gradual process with at least three dis-tinctive stages.

Late Pliocene hominids

The oldest stone artefacts currently known come fromGona, Ethiopia and date to 2.5 million years ago

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had an equivalent patchwork environment (Reed1997; Sikes 1994). The Mt Assirik chimpanzees havea home-range size of 278–333 km2, indicating a home-range radius of 10.3 km (Baldwin et al. 1982). This issimilar to the 13 km minimum home-range radiusfor late Pliocene hominids suggested by raw-mate-rial transfer and anatomical data.

While home-range size may be similar for latePliocene hominids and chimpanzees, the distancesof raw-material transfer are strikingly different. Ob-servations of chimpanzees in the tropical rain forestof Taï National Park (Ivory Coast) show that of 603transports of stone and wood hammers used for nutcracking, 83.5 per cent (n = 504) are over less than 50 m(Fig. 2; Boesch & Boesch 1984). Transport distancesof 50–500 m represent 16 per cent (n = 96), and dis-tances over 500 m represent 0.5 per cent of all ob-served transports (Boesch & Boesch 1984). The TaïNational Park chimpanzees live in a home range of27 km2, indicating a theoretical radius of 2.9 km(Boesch & Boesch 1984). Assuming 500 m as a maxi-mum raw-material transport distance, chimpanzeesmoved objects a distance equal to 17 per cent of theirhome-range radius. On the other hand, archaeologi-cal and anatomical evidence suggests that latePliocene hominids moved objects 100 per cent oftheir home-range radius.

The difference in distances of raw-materialtransfer between chimpanzees and late Pliocenehominids may partly be due to ecological differ-ences, but a more significant factor is the increasedcapacity for planning the use of objects. While achimpanzee is able to pick up a rock with the inten-tion of using it as a hammer 500 m away, chimpan-zees do not demonstrate the capacity to plan for tooluse more than 500 m away or more than a few min-utes into the future. Late Pliocene hominids, by con-trast, were able to pick up a rock with the intentionof using it 13 km away, or at least after one day’sranging. This difference in raw-material transfer pro-

vides evidence of cognitive abilities that distinguishlate Pliocene hominids from chimpanzees.

Late Pliocene hominids did not have language

Although late Pliocene hominids have a greater ca-pacity for planning than chimpanzees, the distancesof raw-material transfer do not suggest that theyused language. Raw material transfers indicate ahome-range size similar to that of chimpanzees in anequivalent environment to Plio-Pleistocene Africa.Data on dental microanatomy and brain size fromlate Pliocene hominids suggest a short maturationperiod and a short life-span similar to those of largeprimates (Smith & Tompkins 1995). Maturation pe-riod, life-span and brain size in primates are corre-lated with social complexity, measured as a functionof group size (Dunbar 1992; 1993; Joffe 1997). Thesimilarity in home-range size and life history be-tween late Pliocene hominids and primates supportsthe analogy of primate social organization and com-munication for late Pliocene hominids.

Chimpanzee social organization, while fluid andflexible, is typified by dominant males who lead themovement of groups. Goodall’s (1986, 207–30) ob-servations of the ranging patterns of the chimpan-zees at Gombe (Tanzania) shows that the movementsof social groups (composed of close kin) are control-led by a dominant individual’s response to the dis-tribution of food and water, the availability of femalesin oestrus, the size and movement of neighbouringcommunities and the presence of predators or otherdangers. A similar pattern of behaviour was observedby Tutin et al. (1983) at Mt Assirik where chimpan-zees formed large, stable, mixed-sex groups for trav-elling. Although Tutin et al. (1983) do not state thatthe group was led by a dominant individual, Goodall(1986, 409–42) observes that large mixed-sex groupstypically have a male dominance hierarchy led by analpha male. Given the similarities in home-rangesize and life history, the chimpanzee model of domi-nant individuals controlling group movement is areasonable proposition for late Pliocene hominids.

The significance of chimpanzees and latePliocene hominids sharing this form of social or-ganization is that it implies that they also sharedequivalent forms of communication. Chimpanzeecommunication consists of sounds, postures and fa-cial expressions that they use to influence the behav-iour of other individuals. Chimpanzee communicationobserved in the wild lacks the three crucial qualitiesof syntax, regular use of symbols and expression ofdisplacement that define human language.

Figure 2. Distances of 603 transports from 4 years ofobservations of wild chimpanzees in the Taï NationalPark (tropical rainforest).

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Dominant individuals in chimpanzee commu-nities act on the basis of private information theyhave acquired through their individual experienceof the environment, and public information acquiredthrough a parasitic process of observing the behav-iours and activities of conspecifics (Garber 2000, 271–2). The dominant individual does not directly seekinformation from other individuals, and other indi-viduals do not have the communicative facility toimpart information relevant to group movement pat-terns. The majority of chimpanzee communicationoccurs between related individuals, with communi-cation between strangers often a long and uncertainprocess that includes display, fighting and injury(Wrangham 1987, 66–8; Goodall 1986, 331, 488–534).The outcome of these factors is that moving groupsof related chimpanzees are led by an individual whonegotiates with other individuals through the use ofstatus and relies on the contents of its own brain tomake decisions.

According to the primate analogy, the earlyhominid communication system was one of non-syntactic expressions with limited use of symbols,produced to alter the behaviour of other individualsin the immediate context. Early hominids lacked theability to express displacement and engaged in the

Figure 3. Transfer distances of raw materials (n = 45) at 14 African sitesor layers, 1.6–1.2 Ma.

Figure 4. Transfer distances of raw materials (n = 41) at 24 African sitesor layers, 1.2–0.2 Ma.

majority of their communicative behaviours withintheir local group. Early hominids depart from theprimate analogy with their increased distances ofobject movement. The increase in absolute brain sizeof early hominids after 1.9 Ma may be responsiblefor the increased capacity for planning suggested bythe transfer evidence. Environmental data suggeststhere were no major selective pressures for largebrains or planning ability at 1.9 million years ago(deMenocal 1995), although recent analysis ofendocasts suggests that brain expansion began a mil-lion years earlier with Australopithecus (Falk et al.2000). An earlier increase in brain size may coincidewith a shift to arid conditions indicated by marineeolian records and faunal records at 2.8 million yearsago (deMenocal 1995). This suggests the possibilityof 13 km transfers from a much earlier period thancurrently available, possibly coincident with the firststone artefacts at 2.5 million years ago.

Non-modern hominids

For the period 1.6–1.2 million years ago there aredata on 45 raw-material transfers from 14 East Afri-can sites or layers (Fig. 3; Feblot-Augustins 1997,inventories 6 & 7). The majority of raw material was

acquired from sources near the pointof discard: 98 per cent of stone forartefacts was procured from a dis-tance of 4 km or less (Feblot-Augustins 1997, inventories 6 & 7).The maximum distance of raw-ma-terial transfer is 15 km, indicatingsimilar strategies of raw-materialprocurement and landscape use tothose of the period 1.9–1.6 millionyears ago where the maximum dis-tance was 13 km. After 1.2 millionyears ago, however, maximum trans-fer distances increase from 15 km to100 km (Fig. 4). Data on 46 transfersfrom six East African sites or layersshow six occurrences of raw-mate-rial transfer between 15 and 100 km(Feblot-Augustins 1997, inventory10). The significance of this increaseis that it demonstrates that after 1.2million years ago, hominid groupshad information about larger areasthan earlier hominids. This indicatesthe appearance of a new ability toexploit larger landscapes for hominidsafter 1.2 million years ago .

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Figure 5. Schematic representation of the three major categories ofraw-material transfer distances and associated communicationabilities. The single hexagon represents the area about which adominant primate or late Pliocene hominid possesses information. Thegroup of seven hexagons represents the area about which a non-modern hominid dominant individual possesses information. This isgreater than that of the late Pliocene hominid because informationcollected by (in this case six) other individuals is pooled through theuse of a protolanguage. The honeycomb represents exchange networkssimilar to those ethnographically observed in hunter-gatherpopulations. These networks permit wide area exchange throughmultiple groups.

Non-modern hominids used aprotolanguage

Anatomical data for non-modern hom-inids suggest a home-range radius of17–49 km (Steele 1996, 249); raw-mate-rial distances, however, suggest a home-range radius of up to 100 km. It is clearthat for non-modern hominids a newvariable has appeared that invalidatesthe anatomical determinism that limitedthe home-range size of early hominids.Data from the periods 2.5–1.2 and 1.2–0.2 million years ago come from the sameareas of equatorial East Africa so thereis no change in ecological conditions(from rainforest to savanna, for exam-ple) that might otherwise explain theincrease in raw-material transfer dis-tances.

I propose that this new variable isthe ability to pool information collectedby individuals through face-to-face ne-gotiation and the use of a protolanguage.The dominant individual could plan anddecide on the movement of the groupwith the benefit of information on amuch larger area than that individualalone could acquire from private andpublic sources (Fig. 5). Mathematicalmodelling by Reynolds & Zeigler (1979)shows that without the ability to poolinformation into a centralized decisionmaker the maximum region accessible toa group is strongly limited by the infor-mation gathering of its individual mem-bers. After the appearance of a proto-language the information collectioncapacity of individual members is nolonger a significant limiting factor, hav-ing been replaced by the limitations ofsocial organizational structure, scalar

Primate and late Pliocene hominidgroup home range and raw-materialacquisition area

Non-modern hominid group homerange and raw-material acquisitionarea

After ~ 130 kya

Section of modernhuman raw-materialacquisition areaindicating raw-material flow throughmultiple groups

protolanguage need not have syntax, the ability toexpress displacement or regular context-free symboluse, and is therefore distinct from modern humanlanguage. The stability of the 100 km home-rangeradius for one million years suggests that the proto-language had long-term stability, while the absenceof any evidence of symbolic behaviour in the ar-chaeological record suggests that extensive use ofsymbols was not common with non-modern hominidsand the expressive power of the protolanguage wasvery limited.

stress and the protolanguage (Reynolds & Zeigler 1979;Johnson 1982).

The exact nature of the protolanguage is notevident from these data and it is not possible todetermine if it was analytic (Wray 2000) or synthetic(Bickerton 1981; 1998). Nevertheless, the attributesrequired for pooling information to increase the ef-fective home range include basic symbolic referenceto perceived phenomena and the ability to commu-nicate about them in simple topic-comment strings(Whallon 1989, 437; Bickerton 1981, 268–9). The

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Further evidence of a protolanguage for non-modern hominids

Coinciding with the increase in transfer distancesare the first signs of Eurasian colonization. Archaeo-logical sites in Europe such as Atapuerca, Ceprano,Monte Poggiolo and Orce and in West Asia such asUbeidiya and Gesher Benut Ya’aqov suggest a ho-minid presence around or just after 1.0 million yearsago (Klein 1999, 314–27). The evidence at these sitesindicates non-intensive and short-term occupation.Although the first traces of colonization appear atthe same time as the increases in raw-material trans-fer distances, the most persuasive evidence of Euro-pean colonization by non-modern hominids occursafter 500,000 years ago. After 500,000 years ago thereare signs of intensive long-term occupation at Euro-pean sites such as Boxgrove, Ambrona, Torralba,Cagny-la-Garenne, Fontana Ranuccio, Isernia LaPineta, Karlich G and Miesenheim 1 (Roebroeks 2001).

The delay in the intensive occupation of Eu-rope from the early attempts at 1.0 million until500,000 years ago is not related to language abilitiesbut probably to the presence of giant hyenas andsabre tooth cats in Europe. Giant hyenas (Pachycrocutabrevirostris) and sabre tooth cats (Megantereon whitei)are carnivorous predators whose dental anatomysuggests that they were hunters of large animals(Arribas & Palmqvist 1999). The presence of thesepredators and the carcasses they discarded providean ecological niche that the first hominid occupantsof Europe at 1.0 million years ago were able to ex-ploit without Acheulean technology (Arribas &Palmqvist 1999). After the giant hyenas and sabretooth cats disappear from the European faunal recordat 500,000 years ago, however, a more stable and pro-ductive hunting niche opened up for hominids usingAcheulean technology (Turner 1990; 1992). Althoughthe human role in faunal assemblages is ambiguousat first, the three 400,000-year-old throwing spearsfrom deposits at Schöningen found in associationwith hundreds of horse bones, many of them withsigns of butchery, provide a compelling case that thesehominids occupied the niche of a hunter (Thieme 1997).

The appearance of a protolanguage amongstnon-modern hominid groups in Africa coincides withenvironmental changes that may have generated se-lective pressure favouring the ability of individualsto expand their group’s home-range size. Oxygen iso-tope evidence of global ice volume and analysis ofwind-blown dust sediments from ocean bed coresindicate a shift in African climate variability from41,000-year glacial cycles to 100,000-year cycles at

1.0 million years ago (deMenocal 1995). Coincidentwith the change to 100,000-year glacial cycles, the Afri-can sediment records suggest a marked increase inglacial amplitude (deMenocal 1995). Further evidenceof an increase in cool and dry conditions in Africa atthis time comes from the fossil record of African bovidaedocumenting increased proportions of arid-adaptedspecies nearly 1.0 million years ago (Vrba 1995).

This intensification of aridity may have pro-vided conditions that selected for more complex com-munication systems. Hurford (1989) and Nowak &Komarova (2001) have used evolutionary gametheory to show that arbitrary bi-directional signswill be selected in preference of other schemes overevolutionary time. The results of Hurford’s (1989)simulation indicate that the Saussurean strategy ofthe arbitrary bi-directional sign can become the domi-nant strategy of communicative behaviour whenthere are selective advantages for successful com-munication. Chimpanzees trained or raised by hu-mans appear to demonstrate greater powers ofsyntactic comprehension and symbol-use than wildchimpanzees, but never greater than that of a twoyear old child (Savage-Rumbaugh et al. 1998). Just aswild chimpanzees demonstrate greater competencein symbol use when trained, so may stressful condi-tions at around 1.0 million years ago have selectedfor hominids capable of using symbols to communi-cate information on resources over a wide area.

Anatomically modern Homo sapiens

From about 500,000 to 70,000 years ago the patternof raw-material transfers in Europe resemble thosein Africa after 1.0 million years ago, with the major-ity of transfers occurring within 15 km of the discardlocation although some occur up to 80 km away (Fig.6). The first evidence of raw-material transport be-yond the 100–120 km barrier occurs in Africa duringthe Middle Stone Age (MSA, c. 250–40,000 years ago).Songhor, Muguruk, Nasera Rock Shelter, GvJm-16,Mumba Rock Shelter (dated by U-series to 100–130,000 years ago) and Porc Epic are excavated sitescontaining MSA stone artefact assemblages with ar-tefacts made from obsidian sourced between 140 and340 km away (Fig. 7; McBrearty & Brooks 2000, 514–15). At GvJm-16, Prospect Farm and Prolonged Drift,the raw material for the majority of stone artefactscomes from local obsidian sources, raising the ques-tion why the occupants of the site acquired obsidianindistinguishable in appearance and mechanicalproperties from distant sources (Merrick et al. 1994, 43).

Transfers of raw materials over 100–120 km,

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half less than 50 km (Hewlett et al. 1986). It is highlyunlikely that Aka individuals would transfer an ob-ject a linear distance of 300 km in the course of theirhabitual activities. Wobst’s (1976) study of matingnetworks amongst recent hunter-gatherers indicatesa maximum distance of 300 km between the mostdistant local groups involved in closed-system mar-riage networks. He predicts that beyond 300 km it ismaladaptive for groups to engage in food sharing,joint ritual and exchange of sufficient intensity tomaintain mate-exchange relations (Wobst 1976, 52).

In light of the ethnographic data, a probableexplanation for raw materials moved over 140–300km is that they moved through networks of exchangeinvolving neighbouring groups. The five AfricanMSA sites with evidence of raw-material transferdistances of 140–340 km therefore suggest the exist-ence of exchange networks (Merrick et al. 1994, 43).

Figure 6. Transfer distances of raw materials at 57 European sites or layers in Europe from Lower Palaeolithic (LP, n= 76) and Early Middle Palaeolithic (EMP, n = 79) 500–70 ka.

such as those observed during the African MSA,suggest indirect procurement. A global sample of 70hunter-gatherer cultures indicates a maximum terri-tory radius of 140 km (mode 15 km, range 3–140 km,mean 32 km, std 24 km) (Kelly 1983; 1995). Thismaximum figure is only approached by groups inthe Arctic regions, such as the Nunamiut andBaffinland Inuit, and the Crow whose mobility isaided by the use of horses (Kelly 1995, 128–9). Rawmaterial sourced to more than 140 km is thereforeunlikely to have been procured during the seasonalmovements of a group. Raw material from 300 kmaway is double this distance and implies access to ahome-range territory more than four times the maxi-mum ethnographically observed.

Ethnographic data summarized by Feblot-Augustins & Perlès (1992) indicate that althoughmovement of around 100 km might be within therange of deliberate forays by mobile foraging groups,transports of raw material over more than 300 kmresult from exchange between groups. Studies of themovement of hunter-gatherer peoples and the spa-tial extents of their alliance networks also indicateexchange networks when distances of around 150–300 km are involved. Ethnographic data on the Akapygmies of the Central African Republic show thatindividuals moved distances of 1 to 175 km, with 96per cent of movement being less than 100 km and

Figure 7. Long-distance raw-material transfer in theAfrican Middle Stone Age.

Site name Location Distance km Date ka Quantity %

Mumba Rock Shelter N. Tanzania 320 100–130 7Nasera Rock Shelter N. Tanzania 240 MSA 4Muguruk W. Kenya 185 MSA 2Songor W. Kenya 145 MSA 1Porc Epic Ethiopia 140 MSA 6GvJm-16 Kenya 105 early MSA 2Prospect Farm N. Tanzania 75 >120 fewProlonged Drift N. Tanzania 45 MSA 90

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Exchange networks and language

Participating in exchange networks requires the spe-cific cognitive and linguistic abilities that define mod-ern humans. Primates do not possess abilities thatallow them to form multi-group exchange networks.Primate social interaction with strangers is typifiedby the uncertainty of the outcome, which may beinjury or death. A second feature that prevents pri-mates from operating exchange networks is theirlimited capacity for exchange. Primates demonstratethe ability for only indirect exchange of goods in-volving immediate reciprocity (Paquette 1992). Forhominids to operate in an exchange network, theyneed to avoid the uncertain outcomes primates havemeeting strangers, and they need to be capable ofdirect exchange with delayed reciprocity.

The ability to express symbolic categorizationsof social systems allows individuals to identify andinteract with unrelated individuals in terms of sym-bolic categories rather than as unique individuals.This allows for relationships based on mutual rightsand obligations rather than the histories of interper-sonal relations that require renegotiation at each en-counter (Whallon 1989, 438). An example of this isthe use of biological kin categories for unrelated ordistantly related individuals in hunter-gatherer andother modern human groups. Expression of displace-ment (beyond the here-and-now) allows individualsto negotiate delayed reciprocity as well as referenceto kin relations that are not biologically-based andare specific to times and places (such as marriagerelations) (Whallon 1989, 439). Syntax is a funda-mental requirement, allowing ideas to be expressedin hierarchical sequences and reference to be madeto multiple subjects and objects, as is required forthe expression of multiple levels of intentionalityand in exchange negotiations.

Further evidence of language during the AfricanMiddle Stone Age

The archaeological record of the African MSA hasother forms of evidence that are congruent with lan-guage-using hominids. This includes the appearanceof regional diversity in the appearance of function-ally equivalent stone projectile points throughoutAfrica during the MSA (McBrearty & Brooks 2000,497–500). This stylistic diversity suggests the emer-gence of bounded ethnic groups within which pro-jectile points are exchanged, similar to exchangenetworks known from the ethnographic record. In-creased planning-depth, economic specialization and

resource scheduling are modern human behavioursthat require language-mediated organization. Faunalremains from MSA layers at Klasies River Mouth,≠Gi and Die Kelders have mortuary profiles sug-gesting species-selection and seasonal activity, as wellas skeletal element representations and cutmarksconsistent with hunting rather than scavenging (Mc-Brearty & Brooks 2000, 506–10). At Katanda (Demo-cratic Republic of Congo) there are barbed bonepoints and an assemblage of large adult catfish bonesoverlaid by sands dated by TL to >90,000 years ago(Brooks et al. 1995; Yellen et al. 1995).

There is also evidence of symbolic behaviour atAfrican sites during the MSA. Body ornaments areknown from at least three African sites dating from130,000 to 40,000 years ago. These include a perfo-rated shell from Oued Djebanna (Algeria), four de-liberately-drilled quartzite flakes from Debenath(Nigeria) and a bone pendant from Grotte Zouhra(Morocco) (McBrearty & Brooks 2000, 521). A pieceof ochre with multiple incised hatchings at Blombos(South Africa) underlies sterile dune sands dated byOSL to 73,000 years ago (Henshilwood & Sealy 1997).At Apollo 11 (Namibia) incised ostrich egg frag-ments have been dated by AAR to >83,000 years ago(Miller et al. 1999).

The evidence of modern human behaviourfound at African MSA sites does not appear in Eu-rope until the transition from the Middle to UpperPalaeolithic around 40,000 years ago (Mellars &Stringer 1989). Data on raw-material transfers fromEurope provide evidence of modern language abili-ties also at around this time. The first evidence oftransfers over distances greater than 140 km occur incentral Europe during the Late Middle Palaeolithic(100–45,000 years ago) and Early Upper Palaeolithic(45–30,000 years ago) (Fig. 8). From a sample of 24sites or layers and 82 occurrences of transfers for theLater Middle Palaeolithic in central Europe there areseven occurrences of raw-material transfers between140 km and 300 km (Feblot-Augustins 1997, inven-tory 30). During the Early Upper Palaeolithic in cen-tral Europe (including transitional industries suchas the Szeletian and Jerzmanowician) there are 55sites or layers and 223 occurrences of transfers, with29 occurrences between 140 and 420 km (Feblot-Augustins 1997, inventories 60, 62).

Evidence of transfer distances in the range 140–400 km do not appear at west European sites untilthe Aurignacian period (35–28,000 years ago), andthe material transferred is not stone but marine andfossil shell (Roebroeks et al. 1988). In the later UpperPalaeolithic (21–11,000 years ago) marine and fossil

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none’ approach to symbol-based communication andreject the notion of a protolanguage. Contrary to theabove scenarios, I propose that a more gradual evo-lution of language can be supported. While someevidence for the appearance of language in Europesuggests it arrived with hominids from Africa, otherevidence indicates that the transition from proto-language to language was occurring in Europe withinnon-modern hominid populations. Neanderthalgroups occupied Europe and west Asia from 300,000to 35,000 years ago, and archaeological evidence sug-gests that their linguistic abilities were intermediatebetween earlier non-modern hominid species suchas Homo erectus and modern humans. As Neander-thal populations span the critical period of languageemergence in Europe and there is a relatively largeamount of data on them, they make a good case forthe study of gradual versus catastrophic languageemergence.

There is ambiguous evidence for some sym-bolic capacity amongst Neanderthal populations.Ochre fragments with signs of scraping have beenfound in a number of Neanderthal sites in southwestFrance, although there is no indication of how theywere used (Mellars 1996a, 20). Over a dozen Nean-derthal burials have been recorded in France andWest Asia, although there is much contention about

Figure 8. Transfer distances of raw materials during the European Late Middle Palaeolithic (LMP, 24 sites or layers,n = 82) and Early Upper Palaeolithic including transitional industries (EUP, 55 sites or layers, n = 233) in central Europe.

shells were transported over 800 km (Feblot-Augustins 1997, figs. 81–4). These very long-distancetransfers suggest the presence of open networkswhere the importance of objects is transformed fromthe functional to the social and ritual realms as theyare circulated through the networks (Feblot-Augus-tins & Perlès 1992). Further developments related tolanguage include the appearance of the first Euro-pean cave paintings and portable art after 30,000years ago, in particular the highly-stylized andwidely-distributed Venus figurines (28–21,000 yearsago) (Klein 1999, 545–53). The production of art andthe very long-distance transfers suggest use of sym-bols, which is a crucial feature of language.

Gradual or catastrophic emergence of language?Neanderthals as a case study

Previous authors have suggested that the emergenceof language was a catastrophic process. Mellars(1996a,b) argues that it is coincident with the behav-ioural transformation that he refers to as the ‘UpperPalaeolithic Revolution’. Bickerton (1998, 354) sug-gests that the transition from protolanguage to lan-guage was a ‘cognitive explosion’ that occurred afterthe emergence of modern humans in Africa. Noble& Davidson (1996, 8) argue in favour of an ‘all-or-

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the role of taphonomic and site-formation processes(Gargett 1989; 1999). Most archaeologists agree thateven if Neanderthals did bury their dead, the ab-sence of convincing grave goods in the burials, andsymbolic artefacts generally, indicates that ceremo-nial and symbolic behaviour was not widespread(Chase & Dibble 1987). A number of sites have in-scribed, perforated or worked bone pieces associ-ated with Neanderthals although there is muchambiguity concerning the role of intentionality andsymbolism in their production (Villa & d’Errico2001; Hayden 1993; Chase & Dibble 1987; 1992).Sites in western Europe, such as Arcy-Sur-Cur andSt Cesaire, and in central Europe, such as Vindijaand Velika Pecina, show associations of Nean-derthals with Upper Palaeolithic technologies thatare variously argued to result from imitation, accul-turation or trading with modern human populations,or to stratigraphic mixing (Karavanic & Smith 1998;Hublin et al. 1996, 226; Lévêque et al. 1993). To sumup the archaeological evidence, Neanderthals wereprobably closer to modern humans that other non-modern hominid species, although they never dem-onstrated the full panoply of modern behavioursobserved in the African MSA and the European Up-per Palaeolithic.

The raw-material transfer data currently doesnot have the resolution to distinguish between mate-rial moved by the last Neanderthals or the earliestmodern humans in central Europe during the Mid-dle–Upper Palaeolithic transition. The hominids as-sociated with the central European transitionalindustries are currently uncertain (Bolus & Conard2001). However, the transitional industries in west-ern Europe (e.g. Châtelperronian) have transfer pat-terns resembling non-modern hominids withdistances not exceeding 70 km (Feblot-Augustins1997, inventory 32). The problem here is that trans-fer data suggests the Neanderthals used a proto-language similar to other non-modern hominids,whereas other archaeological evidence suggests alevel of cultural and cognitive complexity greaterthan previous non-modern hominids. What sort oflanguage lies between the protolanguage of non-modern hominids and modern human language?

Computer simulations and biological evidence

A suggestion can be found in computer simulationsof the evolution of language. These show that com-plex structured languages spontaneously emerge inpopulations of learners even though the populationhas no common signalling system and is not subject

to any biological change (Kirby 2000). Many authorshave argued that syntax is a result of natural selec-tion (Pinker & Bloom 1990; Newmeyer 1991;Bickerton 1998). Recent work, however, suggests thatlanguage itself is a complex adaptive system that is‘more likely to have adapted itself to its human hoststhat the other way round’ (Christiansen 1994, 125).Kirby’s (2000, 305) simulation takes individuals thatlearn observationally (rather than through explicitreinforcement), a gradual turnover of members ofthe population over time (ensuring true transmis-sion of knowledge through the system), no selectionof individuals (death is random to ensure that lin-guistic success is unrelated to adaptive success) andan initial non-linguistic population (so that any bi-ases that emerge in the simulation are a product ofthe model). Communication begins because of ran-dom invention and noise events where an individualproduces a randomly-constructed string of symbols(phonemes or words for example) with a randomly-chosen meaning.

Although the results of Kirby’s (2000) simula-tion are the product of an explicitly non-biologicalprocess, they provide an attractive model for theemergence of syntax in human populations. The re-sults of the simulation show three stages in the evo-lution of syntax (Fig. 9). Stage One is a long andstable period where individuals are able to express asmall number of the total meanings possible in thesimulation using a small grammar. Grammars dur-ing this first stage are not sets of rules but vocabu-lary lists with meanings expressed as arbitraryunanalyzed strings of symbols. Kirby (2000, 317) de-scribes Stage One as a communication system that is‘nothing more than an inventory of calls expressingunanalyzed meanings’ with ‘an impoverished, idi-osyncratic vocabulary of one-word utterances’. Thelack of syntax and the stability of the communica-tion system in Stage One is analogous to the proto-language of non-modern hominids that emergedaround 1.0 million years ago and lasted until about130,000 years ago.

Stage Two is a period of unstable and unpre-dictable changes. The size of the grammar and thenumber of meanings expressed increases dramati-cally, but fluctuates wildly. An important changefrom Stage One is that the number of meanings be-comes greater than the number of rules in the gram-mar. Kirby (2000, 317) describes the language of StageTwo as ‘brittle . . . and liable to break and lose itsexpressive power suddenly’. He notes that the gram-mars at this stage are more complex than Stage Oneand that ‘the details of what is going on in the lan-

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100guage of the population at thisstage are hard to figure out’(Kirby 2000, 314). I believe thatthis stage is a reasonable ap-proximation of Neanderthallinguistic abilities, with their be-havioural capacity somewherebetween earlier non-modernhominids and modern humans,but raw-material transfers firmlyin the range of earlier non-mod-ern hominids. The type of lan-guage emerging at Stage Two ofthe simulation may have permit-ted more complex social organi-zation and behaviours withinlocal kin groups, but it lackedthe stability and flexibility tomaintain multi-group networksover large areas and long peri-ods. This lack of stability andflexibility may explain why Ne-

thals and modern humans probably produced dif-ferent patterns of linguistic evolution that resultedin modern humans arriving in Europe with languageand replacing the less loquacious Neanderthals.

While Kirby’s simulations suggest a gradualprocess of language evolution, and help us to under-stand the abilities of the Neanderthals, furthersimulations by Tonkes & Wiles (2002) reveal inter-esting details relating to the length of the learningperiod and the population size. Their simulationsshow that populations converge on languages re-gardless of their size, but that the time taken to con-verge is greater in larger populations. In largerpopulations, the communicative error rate is higherand the possibility of two or more different lan-guages emerging is higher, taking greater time forone language to dominate and the error rate to stabi-lize at a tolerable level. This suggests that a rela-tively small population size was optimal for theemergence of language and exchange networks.

Genetic evidence, such as segregating Alu in-sertions, mitochondrial mismatch distributions, X-and Y-chromosome microsatellite loci and proteinpolymorphism, indicate a suite of coalescent eventsbetween 180,000 and 120,000 years ago (Goldstein etal. 1995; Hammer et al. 1997; Harding et al. 1997;Harpending et al. 1993; Harris & Hey 1999; Nei &Roychoudhury 1974; Stoneking et al. 1997). Har-pending et al. (1998) and Reich & Goldstein (1998)interpret these coalescences as the result of a popu-lation bottleneck roughly coincident with a glacial

Figure 9. Kirby’s simulation of the non-biological evolution of syntax. (FromKirby 2000.)

anderthal raw-material transfer distances are similarto those of earlier non-modern hominids, and whyNeanderthals did not develop cultural behavioursthat became persistent and widespread.

Following an abrupt transition, the third stageof the simulation appears with a sudden increase inthe number of meanings that can be produced, to themaximum value allowed by the simulation and adrop in the size of the grammars (Kirby 2000, 314).There is now a regular correspondence betweenmeanings and expressions and the individual’s gram-mars are compositional and have syntactic categoriesfor nouns and verbs. This stage constitutes a simplesystem with long-term stability and great expressivepower. The third stage is an ideal analogue for theemergence of modern language, with syntax andmassive expressive power controlled by a UniversalGrammar consisting of a few general rules.

Although it seems likely that Neanderthals wereoperating with a Stage Two language, whether ornot they made it to Stage Three may never be known.Non-biological linguistic evolution and biological andcultural evolution influence each other in ways thatare difficult to predict (Kirby & Hurford 1997; 2001).Mathematical models of language evolution showthat once language abilities appear in a populationand certain demographic and information thresh-olds are reached, evolutionary processes select forlanguage in favour of other communication systems(Nowak & Krakauer 1999; Nowak et al. 2001). Bio-logical and cultural differences between Neander-

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phase peaking around 130,000 years ago (Lahr &Foley 1998, 163–4). In light of the simulations ofTonkes & Wiles (2002) the population contraction at130,000 years ago is an optimum condition for theemergence of language, allowing its spread to berapid and minimizing the possibility of maladaptiveand prolonged communicative errors and multiplemutually unintelligible languages.

These simulations also show that longer learn-ing periods vastly reduce the communication errorrate in a population. Dean et al. (2001) analyzed dailyincremental markings in enamel to calculate rates ofenamel formation in 13 fossil hominid specimensdating between 4.0 million and 120,000 years ago.They found that the slow trajectory of enamel growthduring prolonged maturation typical of modern hu-mans appeared relatively late in hominid evolution,at around 120,000 years ago (Dean et al. 2001). Thisevolution of a longer maturation and learning pe-riod (also called the critical period) may have beenthe final anatomical precondition for the emergenceof language following the lowered larynx, an appro-priately shaped hyoid bone, muscular control of thetongue and chest and an adequate angle of basicra-nial flexion.

Conclusion

Distances of raw-material transfer by Pleistocenehominids show three important stages that relate tolanguage ability. The first stage begins at about 1.9million years ago with a maximum raw-materialtransfer distance of 13 km and shows early hominidsto have had a capacity for planning greater thanchimpanzees. The second stage occurs at about 1.0million years ago when the maximum transfer dis-tance increases to 100 km, suggesting the presence ofa protolanguage that facilitates pooling of informa-tion. This enabled African non-modern hominidgroups to exploit much larger territories than before.The protolanguage allows basic topic-comment ex-pressions and symbolic reference, and simulationssuggest that it was analytic rather than synthetic (cf.Wray 2000). The protolanguage may have been se-lected for during the intensified aridity of the Afri-can climate 1.0 million years ago.

The third stage is marked by maximum trans-fer distances of >300 km, first appearing in Africa130,000 years ago and after 100,000 years ago inEurope. This third stage represents the emergence ofexchange networks that require a communicationsystem allowing expression of displacement and sym-bolic categorization of social systems, namely hu-

man language. At around 130,000 years ago biologi-cal evidence suggests small population sizes and theappearance of a delayed maturation in human lifehistory, features that computer simulations indicateare optimum conditions for the evolution of language.

I have argued using archaeological evidenceand computer simulations that language evolutionwas a gradual process. A computer simulation pro-duced by Kirby (2000) shows that non-biological evo-lution can transform a protolanguage into a language.I propose that the intermediate stage of languages(Kirby’s Stage Two) that are highly unstable andhighly variable in their complexity and expressivepower may explain the paradox of the Neanderthalswho may have been capable of some near-modernbehaviours but did not use exchange networks. Asignificant detail of Kirby’s simulations is the impor-tance of non-biological linguistic evolution. This in-troduces a third factor that I have attempted toinclude in my model, along with biological and cul-tural evolution. Given the lack of genetic change orspeciation events in hominid populations during theMSA, it is possible that linguistic and cultural evolu-tion were the main forces behind the emergence oflanguage.

Although in early stages of development, thenarrative presented here has the advantage over pre-vious ones of being capable of testing through thecollection of additional data on raw-material trans-fers in Africa, Europe and Asia. If the timing andpatterning of the crucial thresholds of 13 km, 100 kmand 300 km are shown to be unreliable and fail to beconfirmed in future research (which should considerdata from China, central Asia and southeast Asia)then the narrative proposed here can be rearrangedor rejected altogether. Alternative methods for cal-culating home-range sizes with raw-material trans-fer distances could also be used to test this model,such as minimum convex polygons and the adaptivekernel methods (Gamble & Steele 1999).

Acknowledgements

Versions of this paper were presented at the FourthInternational Evolution of Language Conference2002, the Australian Functional Systemic LinguisticsAssociation Conference 2002 and the UWA Instituteof Advanced Studies Language in Time Symposium2002. Thanks to the organizers of these events for theopportunity to present this work and obtain feed-back. Thanks to Jane Balme for reading an earlierversion of this article. Thanks also to Michael Arbib,Iain Davidson, Terrance Deacon, Huck Turner, Janet

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Wiles, Simon Kirby, Jim Hurford and John Hender-son for their comments on presentations of this arti-cle. Thanks to one of the referees for some acuteobservations.

Ben MarwickCentre for Archaeology

University of Western Australia35 Stirling Hwy

Crawley 6009Western Australia

Email: benmarwick@hotmail.com

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Author biography

Ben Marwick has studied archaeology at the University ofMichigan and the University of Western Australia wherehe recently completed a MA thesis in Australian Aborigi-nal archaeology. His research interests include the evolu-tion of modern humans and Australian Aboriginalarchaeology. Ben is currently a tutor at the University ofWestern Australia Centre for Archaeology.

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