General comments on sampling strategies at a site level

The sampling strategies that have been applied at each site are diverse (there is abundant literature on this topic, see e.g. Orton 2000, Jacomet et al. 2009) . Only part of the sites were sampled by or supervised by myself, while the rest were sampled either by the archaeologists themselves (without any advice) or in collaboration with other archaeobotanists. The sites in which I collaborated in some way in the formulation of the sampling strategy or the recovery of the samples are: La Draga, Can Sadurní Cave, Sant Llorenç Cave, Camp del Colomer, Espina C, Pla del Gardelo, El Collet, Serra del Mas Bonet, 120 Cave and La Dou.

The sites that were sampled by other archaeobotanists are Bòbila Madurell and Sardo Cave. Codella, Gavà Mines, C/Reina Amàlia 31-33, CIM “El Camp” and Cova Fosca were sampled on the sole initiative of the archaeologists.

Firstly, it is necessary to briefly state the target population that one aims to sample. Ideally, this should be the total quantity of seed and fruit remains that were discarded in an archaeological site. Of course, reaching this target depends on what proportion of these remains have preserved in the archaeological sites/features that have been excavated (what other authors may call the “sampled population” (van der Veen 1985)).

Usually, especially in dryland sites, this is a very small proportion and, as stated by other researchers, only a modest part of the assortment of plants used in these sites will be known through this analysis (e.g.

(Jacomet, Brombacher & Dick 1989, Out 2009). In any case, all interpretations that will be elaborated from the archaeobotanical data presented in this work necessarily assume that there is, to a certain extent, some positive correlation between what is preserved and what was obtained, processed, consumed and discarded in the past. Otherwise, this work would be meaningless. Many works have targeted the chances of plant macroremains of getting charred, basically as refuse of the processing and consumption of cultivated plant foods (e.g. (Willerding 1971, Hillman 1981, van der Veen 2007), or by using dung as fuel (Miller 1984, Charles 1998, Valamoti & Charles 2005, Valamoti 2013). The process of carbonization allows their long-term preservation in dry mineral sites.

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The desired number of plant macroremains that should be obtained in each sample is c. 400 items (after (van der Veen & Fieller 1982). If the sample was obtained in a representative way (from all the surface of the context, rather randomly taken), this population gives representative proportions of the better-represented taxa (= over 10% of the total) with an accuracy of 95% ± 5%. In the majority of occasions, such number of remains was impossible to obtain at a sample or context level. This is a frequent case for dryland sites (with the exception of burnt storages). In that case the target was aimed for each chronological phase of a site (partly following van der Veen 1985).

Previous works in sites with anaerobic preservation demonstrated that the botanical diversity is much larger than in dryland situations and that larger subsamples are needed in order to have a reliable proportion of the most significant taxa. The desired number of items per sample, then, was increased to around 800 items (400 per sieve fraction) (Hosch & Jacomet 2001). This number could rise even more when the recording of the whole botanical diversity of a rich sample is aimed (Vandorpe and Jacomet, unpublished). It must be noted that, ideally, these numbers should be obtained through a random sampling of the whole site. This was hardly viable in any of the sites that were included in this work, since excavations never affected complete settlements. Consequently, systematic samples were taken as far as possible in order to obtain data that can be considered as representative of the excavated area.

The different existing types of archaeobotanical samples were clearly described by M.K. Jones (Jones 1991):

- grab sampling: which includes the study of chance finds and data from past frameworks of research;

- judgement sampling: these samples are taken on the basis of assumptions concerning the

“population” that is being sampled;

- interval sampling: taken with an even spacing across a “population” of material;

- and probabilistic sampling: through which the probability that the sample reflects the population from which it came can be statistically assessed.

Figure 3.21 shows the types of sampling strategies that have been used and the sites where they have been used. type of context, the richness of organic content of the sediment, etc.

Serra del Mas Bonet, Camp del Colomer, C/Reina Amàlia 31-33, La Dou, Codella, El Collet, Espina C, Pla del Gardelo, CIM “El Camp”, Gavà Mines Probabilistic sampling: 20% of the sediment of

all contexts

Cova del Sardo Grab sampling: manual collection and

judgement samples

Cova Fosca

Fig. 3.21. Sampling strategies applied per site.

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These sampling strategies resulted in very different quantities of volume of soil processed: from less than 15 litres in Fosca Cave to an unknown volume of over 1000 litres in Bòbila Madurell. Consequently, very different results were obtained: from 1 item up to 49322 remains. Some sites produced very large amounts of items even though a relatively low volume of sediment was sampled, like La Draga, while other sites yielded very few remains despite the large volumes of sediment that were processed (for instance, Sant Lorenç Cave, CIM “El Camp” or Sardo Cave).

Seventeen sites and thirty-four settlement phases have been analysed in this work (for an overview, see Fig.

3.22). The total number of samples that have been taken is close to 1200. Unfortunately, more than 400 were either not possible to ascribe to any chronological phase or belonged to other chronological periods (from the Upper Paleolithic to the Modern Ages). This affected quite dramatically the numbers presented for some particular sites like Sant Llorenç Cave or CIM “El Camp”, where the chronological classification of the samples was particularly complicated. Only those samples that have been chronologically ascribed to the Neolithic period will be considered. Some other sites with structures or layers from the Neolithic period were sampled and processed but they either yielded no seed and fruit remains, or had very few remains and only identified to family level, or were not ascribed to any particular phase within the Neolithic period. That is the case of Pesseta Cave (Antolín 2008a), Camí dels Banys de la Mercè (Antolín 2007), Cingle del Mas Nou (Alonso and Antolín, unpublished) and Can Roqueta – Can Revella (Antolín 2008c), respectively.

These sites were not included in the analysis.

The average number of samples per settlement phase is 22.4 (being 1 the minimum and 243 the maximum).

The average volume of sediment is somewhat above 200 litres, 8 being the minimum and around 900 the maximum. All in all, 337 contexts were sampled, of which 213 gave positive results concerning plant remains (an average of 6.3 per settlement phase). A total number of 95148 seed and fruit remains were obtained within these samples, nearly 2800 per settlement phase (Fig. 3.22). Unfortunately, these results are not equally homogeneous and there are 26 settlement phases that did not reach the desired number of items per phase.

The volume of the samples should be in accordance with the target number of remains that one expects to recover. The size of the samples is also significant for other issues, since large items have less possibilities of being represented in small samples. Consequently, a systematic strategy based on small samples (probably below 10 litres in a dry site and below 3 litres in a wet site with waterlogged preservation) systematically neglects the representation of the larger fruits (see, for instance, Hosch & Jacomet 2001, Jacomet 2013). The optimal method is taking (and analysing) test-samples (Pearsall 1989, Buxó 1997, Alonso 1999), but this strategy was not possible, for which I relied on previous experiences. Consequently, most of the times the archaeologists were requested to sample c. 20 litres of sediment per sample at least (I never gave a maximum). But, as observed in Fig. 3.21, the strategies have been very diverse and they will be specified on a site-by-site basis in Chapter 4.

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Fig. 3.22. Number of samples, total volume of sediment, number of contexts, of contexts with positive results on archaeobotanical remains and total number of remains presented per settlement phase studied in this work (only those samples of which the archaeobotanical remains have been fully quantified are included in

this table).Early Neolithic: 5400-5000 cal BC; Late Early Neolithic: 5000-4500 cal BC; Early Middle Neolithic: 4500-4000 cal BC; Middle Neolithic: 4000-3200 cal BC; Late Neolithic 3200-2300 cal BC.