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`Fish-tail' projectile points and megamammals: new evidence from Paso Otero 5 (Argentina).

Introduction

Recently, archaeological knowledge of early human occupations in the Pampean region of Argentina has improved through new archaeological sites dated to c. 10,000-11,200 BP. Archaeological research carried out in Tandilia Serrana Area, at sites such as Cerro El Sombrero and Cerro La China (Flegenheimer 1980; 1986-87; Zarate & Flegenheimer 1991), as well as Cueva Tixi, Los Pinos, Burucuya and Cueva La Brava (Mazzanti 1996; 1999), have yielded significant archaeological contexts related to the Pleistocene-Holocene transition containing the so-called `fish-tail' projectile points. In the grasslands of the Interserrana Bonaerense Area the situation is quite different because only two sites can be related to the Pleistocene-Holocene transition: Arroyo Seco 2 (Politis 1997) and the recently excavated Paso Otero 5 (Martinez 1997).

The objectives of this paper are to summarize the results obtained from Paso Otero 5 (Pampa Humeda subregion, Pampean region, Argentina) and to discuss their contribution to the knowledge of projectile points and megamammals related to early human occupations in southeastern Buenos Aires Province. The so called `fish-tail' projectile points have played a particularly important role in South American prehistory, given the fact that they have been used as cultural and chronological markers in monitoring the dispersal of early hunter--gatherers (see discussion in Nami 1997 & Politis 1991). The presence in this archaeological context of a good record of extinct megamammals also raises the issue of the behavioural implications of the management and procurement of these species and the impact of humans on processes of extinction and survival of megamammals into the Holocene (see Politis & Gutierrez 1998).

Background information: Paso Otero 5

The Paso Otero 5 site (38 [degrees] 12'08"S/59 [degrees] 06'58"W) is located in the middle basin of the Quequen Grande river (Necochea District) in the Interserrana Bonaerense Area, a grassland plain surrounded by the Ventania and Tandilia mountain ranges (FIGURES 1 & 2). The site was found on the right bank of the river in 1994, when a concentration of burned and non-burned megamammal bones was recorded projecting from the bank, suggesting the presence of an archaeological site. Subsequently, three excavation seasons were carried out from 1995 to 1997, covering an area of 20 sq. m (Martinez 1997).

[ILLUSTRATIONS OMITTED]

The stratigraphic sequence in the middle basin of the Quequen Grande river is composed of sediments of the Lujan Formation, which in turn consists of the late Pleistocene Guerrero and the early to middle Holocene Rio Salado Members (Tonni & Fidalgo 1978). The former consists of fluvial and aeolian facies and the latter is a stratified fluvial deposit that records a pattern of alluviation-stability-alluviation (Johnson et al. 1998). The Rio Salado Member is formed from lagoons and swamp deposits. Diatomaceous deposits are also recorded in different parts of the basin (Zarate et al. 1998: 139). In Paso Otero 5, the sedimentary column of this member shows six periods of landscape stability represented by the development of buried `A' horizons (FIGURE 3). The sixth stabilization surface (Ab6), a palaeosoil named Puesto Callejon Viejo that separates the two members of the Lujan Formation, is placed on the transition from the Pleistocene to the Holocene. With the exception of a few isolated items present in the contacts between Ab6 and the Rio Salado and Guerrero Members, the archaeological de posit was recorded within this buried `A' palaeosoil (Holliday et al. forthcoming; Martinez 1997).

[ILLUSTRATION OMITTED]

Lithics

Forty-seven lithics have been found, among which fine-grained quartzite predominates (60.8%), with some basalt and chert. The procurement of raw materials such as quartzite and chert was carried out in the Tandilia hills (50-70 km northward), while basalt probably came from the Atlantic coast.

Very small flakes and debris are the most frequent artefact category (93-5%), although two formal tools were found. The most important tool is a so-called `fish-tail' projectile point. Despite the stem and the tip being partially fractured, the shoulders can be clearly observed. It is important to note that the remaining piece of the stem shows marginal grinding edges and considerable thickness, attributes that are diagnostic of the `fish-tail' projectile points (Flegenheimer 1986: 3; see Nami 1997). This tool was made from `red chalcedony' (silica micro-cryptocrystalline), shows a lanceolate form and was manufactured by unifacial marginal reduction. The other is a red quartzite tool, classified as multi-purpose, with a borer-like point, two large notches and a marginally retouched edge.

In summary, technological evidence indicates that the lithic flakes and debris are the internal by-products of the knapping of blanks prepared in advance and transported to the site, and thus do not contain remnants of cortex. The scarcity of artefacts and tools at the site, as well as the fact that the majority of flakes and debris are small, suggests a lithic production related to the final stages of preparation, secondary trimming, resharpening and possibly replacement of artefacts (Martinez 1999).

Faunal remains

To date, c. 3000 bone fragments have been analysed. Of these, only 32 were identified to species level (TABLE 1):Megatherium americanum (giant ground sloth), Equus neogeous (American horse), Toxodon sp. (Toxodon), Hemiauchenia (extinct camelid), Lama guanicoe (guanaco), Glossotherium sp. (ground sloth)(1), Xenarthra and Pilosa indet. Furthermore, the presence of Glyptodon sp. (giant armadillo) is indicated by an armour plate. It is remarkable that at least six species are present at the site, five of which were megamammals. The best represented species is Megatherium americanum (59.3%). The majority of skeletal parts of all recorded taxa belong to the appendicular skeleton (62-5%). Considering the stages of dental eruption and epiphysis fusion, it is possible that Equus neogeous is represented by two individuals (mature and juvenile) while the rest of the taxa are represented by at least one individual (Martinez 1999).
TABLE 1. Quantification of Paso Otero 5 faunal remains.

taxa N (%) axial appendicular

Megatherium Americanum 19 (59.3) 5(*) 13
Toxodon sp. 2 (6.25) -- 2
Glossotherium sp. 2 (6.35) 1 1
Equus neogeous 2 (6.25) 1 1
Hemiauchenia sp. 1 (3.1) -- 1
Lama guanicoe 2 (6.25) -- 2
Xenarthra indet. 3 (9.32) -- --
Pilosa indet. 1 (3.1) 1 --
total 32 8 20
 (25%) (62.5%)

taxa N (%) indeterminate

Megatherium Americanum 19 (59.3)
Toxodon sp. 2 (6.25)
Glossotherium sp. 2 (6.35)
Equus neogeous 2 (6.25)
Hemiauchenia sp. 1 (3.1)
Lama guanicoe 2 (6.25) 3
Xenarthra indet. 3 (9.32) 1
Pilosa indet. 1 (3.1) 4
total 32 (12.5%)

(*) including one tooth fragment


A sample of the unidentified small bones (N=562 or 63%) shows evidence of exposure to fire, demonstrated by mixed stages of nonburned, burned, carbonized and calcined bone structures, as well as combinations of these stages (Joly pers. comm. 2000). A further re markable feature was a concentration of burned bones surrounding a calcaneous (Megatherium americanum) and a megamammal vertebra (Xenarthra) (FIGURE 3).

The amount, variety and size of fire-modified bones requires special attention regarding the cause of the burning. It is argued that the burned bones of Paso Otero 5 were not produced by a natural fire. First, the existence of natural fires is unlikely in a palaeosetting, characterized by a buried `A' horizon formed in moist conditions near lagoons or river banks (e.g. floodplains). Secondly, data collected from natural grassland fires indicate that the heat is not great enough for a long enough period to alter bone colour beyond scorching (Seabloom et al. 1991; Johnson pers. comm.). Therefore, the variety of burning stages and colours recorded at Paso Otero 5 strongly suggest human-induced burning. Furthermore, the idea that the burned bones are only the result of cooking, consumption and discard is difficult to support. Given the intensity of combustion revealed on the bone surfaces, it is suggested that bone was primarily used as fuel, as well as indicating the possible consumption of prey at the site.

The high degree of bone combustion resulted in high fragmentation, which in turn makes it difficult to observe extensive bone surfaces in order to record patterns of modification (exfoliation, root-etching, carnivore gnawing, cutmarks, etc.) to determine the presence and frequency of either post-depositional processes or human action. In the consideration of evidence of animal exploitation, bone fracture pattern has been a better analytical device for dealing with human activities. A tibia of Hemiauchenia sp. presents a helical fracture pattern; other megamammal diaphysis fragments exhibit blow marks and radial intersecting fracture fronts. Thus, at the present time, only one species presents direct signs of being exploited, probably for marrow extraction.

Interpretation of the archaeological context

Two burned bone fragments of megamammals taken from the bone concentration were dated to 10,190 [+ or -] 120 BP (AA-19291) and 10,440 [+ or -] 100 BP (AA-39363) (FIGURE 3). Organic matter sample (humates) taken from the Ab6 soil at Paso Otero 5 gave an age of 9399 [+ or -] 116 BP (DRI-3573; Holliday et al. forthcoming). The sample taken from this soil in the Paso Otero 1 site (located on the opposite bank of the river to Paso Otero 5) yielded a date of 9950 [+ or -] 65 BP (DRI-2834; Johnson et al. 1998: 20). Taking into account that [sup.14]C ages obtained from organic matter fractions from soils are always interpreted as `minimal ages' (see discussion in Holliday et al. forthcoming), the date from the Ab6 in Paso Otero 5 is therefore highly consistent with both the AMS ages obtained from bones of this site and with those obtained from the same soil at Paso Otero 1.

On the basis of the evidence provided by faunal and lithic remains in association with a buried soil developed in an unstable setting such as a floodplain, it is suggested that Paso Otero 5 represents a specific purpose site, where activities were probably related to the small, ancient river bed. Such activities would have included procurement, primary and secondary processing of megamammals killed nearby, and artefact production involving the final stages of the lithic reduction sequence (e.g. secondary trimming and edge reactivation).

An aspect that requires further study is the presence of at least five species of megamammals in this archaeological context. Given the size of these animals, the idea of simultaneous procurement is difficult to support. Although further study of the site formation processes is essential, it is proposed that the site was not formed through a single event but rather by several hunting/scavenging tasks, suggesting that the same place in the landscape was reoccupied by hunters. The fact that bone was used as fuel implies the possibility of a procurement strategy of bone raw material near the site, which would explain the large number of taxa in the archaeological deposit.

Discussion and conclusion

For the early archaeological occupations of the southeastern part of Buenos Aires Province, most of the earlier sites such as Cerro El Sombrero, Cerro La China, Cueva Tixi, Abrigo Los Pinos, Cueva La Brava and Cueva Burucuya were found in the Tandilia mountain ranges, and have a chronological span of 11,200-8000 BP (Flegenheimer & Zarate 1997, Mazzanti 1999). In the Interserrana Bonaerense Area, the site of Arroyo Seco 2 has an occupation range of c. 11,200-7300 BP (Politis 1997) and Paso Otero 5 of c. 10,200-10,450 BP. Taking into account these two areas, sites located in the Tandilia hills contain assemblages with a large number and variety of lithic artefacts, among which the `fish-tail' projectile points are well represented (e.g. Cerro La China 1 y 2, Zarate & Flegenheimer 1991; Cerro El Sombrero Abrigo 1 and Cerro El Sombrero hill-top, Flegenheimer 1991; Abrigo Los Pinos, Mazzanti 1999).

Although there have been surface finds of this type of projectile point in the Interserrana Bonaerense Area (see Flegenheimer & Bayon 1996; Politis 1991), the specimen found at Paso Otero 5 is the first recorded in a clear stratigraphic context, associated with other human activity (burned and intentionally broken bones, lithics, etc.) and with a chronology related to the Pleistocene-Holocene transition.

Due to problems of preservation and probably site functionality, the finding of faunal remains in the Tandilia range is rare. One exception is the earliest occupation of Cueva Tixi(2) where 16 genera of extinct and modern species were recorded (Mazzanti & Quintana 1997). Bones belonging to extinct mammals such as Eutotus seguini (extinct Dasypodidae) and Canis D. avus (extinct Canidae) were found in association with modern species. By contrast, a good record of species has been obtained in the Interserrana Bonaerense Area. In the Arroyo Seco 2 site, 24 species were recovered from the lower component, nine of which belonged to extinct megamammals: Eutatus seguini, Mylodon sp., Glossotherium sp., Toxodon sp., Macrauchenia sp., Glyptodon sp., Hippidion sp., Equus sp. and Megatherium sp. (Miotti & Salemme 1999). Good representation of faunal remains in the Interserrana Bonaerense Area is also shown in the early Holocene component (c. 7000-7500 BP) of the La Moderna site, where specimens of Doedicurus clavicaudatus and other modern species were also found (Politis & Gutierrez 1998).

There are clear differences in presence and spatial distribution of `fish-tail' projectile points and archaeological contexts with megafauna within the southeastern portion of Buenos Aires Province. Megamammal bones are much better represented in the plains, while lithic assemblages containing `fish-tail' projectile points predominate in the hills. The exception which bridges both patterns is Paso Otero 5, where both types of evidence were recorded associated in the same archaeological context. As such, the archaeological record recovered from this site provides important information which not only increases the available knowledge of early occupations of the plains, but also allows important comparisons to be made with the archaeological record of other areas in the Pampean region.

Acknowledgements. I thank Gustavo Politis, Maria Gutierrez, Eileen Johnson and Benjamin Alberti for their valuable comments and suggestions. Gustavo Gomez assisted the preparation of figures. The project INCUAPA (UNCPBA) supports the research at the site.

(1) Elsewere (Martinez 1997), clue to the presence of dermal bones, it was suggested that Scelidotherium sp. or Mylodon sp. were probably present at the site. However, through new analysis carried out on recently recovered bone specimens it has been possible to identify Glossotherium sp. Consequently, it is more probable that the dermal bones belong to this last genus.

(2) Additionally, there is a Eutatus seguiniplate recovered from the Cerro La China 1 site (Flegenheimer 1986-1987).

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GUSTAVO A. MARTINEZ, CONICET-INCUAPA, Facultad de Ciencias Sociales, UNCPBA, Del Valle 5737, (B7400JWI) Olavarria, Provincia de Buenos Aires, Argentina. gmartine@soc.unicen.edu.ar

Received 11 January 2001, accepted 22 Feburary 2001; revised 1 June 2001
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Author:MARTINEZ, GUSTAVO A.
Publication:Antiquity
Article Type:Statistical Data Included
Geographic Code:4EUUK
Date:Sep 1, 2001
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