Radiocarbon dating of the plant material is important for chronology of archaeological sites. Therefore, a selection of suitable plant samples is an important task. The contribution emphasizes the necessity of taxonomical identification prior to radiocarbon dating as a crucial element of such selection. The benefits and weaknesses of dating of taxonomically undetermined and identified samples will be analysed based on several case studies referring to Neolithic sites from Hungary, Slovakia and Poland. These examples better illustrate the significance of the taxonomical identification since plant materials of the Neolithic age include only a limited number of cultivated species (e.g. hulled wheats) and typically do not contain remains of late arrived plants (e.g.
- plant materials
- taxonomical identification
- radiocarbon dating
It is stating the obvious that the dating with radiocarbon methods is one of the most important tools ordering our knowledge of the past. It allows the cultural and environmental phenomena from the past to be placed on a timescale. It also makes it possible to establish absolute chronology (Bronk Ramsey, 2001; Buck
However, radiocarbon dates obtained from plant material are often regarded with caution, because, for a number of reasons, they do not provide reliable results. Among these reasons one should mention the following:1) lack of connection between plant material and archaeological context, 2) different fossilisation of plant remains within the same sample, 3) lack of taxonomic identification of plant remains, 4) impact of the ‘old wood’ problem.
This last factor requires a brief comment. The effect in question may stem from burning old, dead wood from a tree that had grown in a given area much earlier than it became settled. But problems may also stem from dating a charcoal sample originating from a trunk belonging to one of long-lived tree species. The trunk might have been cut and used in the cultural context that we want to date (Schiffer, 1986, 1996), but the ‘old wood’ effect results in the dates being inevitably older than the context from which the sample was taken. As a result, the chronology of the dated site or prehistoric phenomenon will be to a smaller or larger extent incorrect.
This danger becomes fully apparent when we compare the dates obtained from charcoal with those obtained from other organic substances, in which the discussed effect does not appear, and which originate from the same context. This was very convincingly demonstrated in a classic study by W. Stöckli (2002: fig. 13), where three Linear Band Pottery culture (
The problem of the ‘old wood’ has been raised many times in archaeological literature (Schiffer, 1986; Nowaczyk, 1990; Whittle, 1990; Lityńska-Zając, 1994; Housley, 1999; Dobrzańska
An example of dangers associated with the lack of such identification may be the Upper Palaeolithic site Egerszalók-Kővágó, in northern Hungary (Kozłowski
Similar examples provided the Upper Palaeolithic site of Kostienki 12 (near Voronezh in western Russia), where among the charcoals of coniferous wood, like
Certainly, charcoals and seeds or fruits are an integral component of archaeological data set that is as important for reconstruction of past reality as e.g. ceramics or lithics. In other words, besides the absolute chronology of archaeological features and artefacts, radiocarbon dating of identified plant remains might significantly contribute to the history of local vegetation and food production systems of a given prehistoric or historic community.
The benefits and weaknesses of dating of archaeobotanical samples will be analysed based on some case studies from Hungarian (Nagykörű, Polgár-Bosnyákdomb, and Polgár-Csőszhalom), Slovak (Moravany), and Polish (Ludwinowo and Mozgawa) archaeological sites, referring to Early and Middle Neolithic periods (Fig. 1).These case studies have been performed by authors of the presentation within several research projects.
Nagykörű, located in the central part of the Great Hungarian Plain, is the site of the Körös culture (Raczky
The radiocarbon dating of the site (Fig. 2) was based on four undetermined charcoal fragments (VERA-3052, VERA-3474, VERA-3476, VERA-3540 – Raczky
Therefore, the start and end of the settlement should be set at approx. 5900/5800 and 5700/5600 cal BC, respectively. Consequently, the thesis about the existence of the settlement already in the 60th century BC, which is in contradiction with current views on the spread of the Körös culture, should be rejected. In other words, we consider the date VERA-3476 as an effect of ‘old wood’.
The dating of
In the village of Moravany, in the Eastern Slovak Lowland, there is a settlement of the early and partly the middle phase of the Eastern Linear Pottery culture (
Twenty radiocarbon dates were obtained from undetermined taxonomically charcoals (Fig. 3: 1) gathered in anthropogenic features of that culture at the settlement of Moravany (Nowak, 2015). These dates are characterized by a great dispersion, from the Last Glacial Maximum until the beginning of the Eneolithic period. Obviously, this is a time span far beyond the span of the entire AVK (
In contrast, dates obtained from the
By way of a kind of interpolation, we presume that all datings older and younger than the Early Neolithic should be associated with plants untypical for the mid-Holocene environment. Their presence in anthropogenic features demonstrates that cultural and natural post-depositional processes, which influenced content of these features, were active in the area of the site. Older charcoals, could get there, firstly, during digging of pits, as a result of cutting lenticular concentration of the Late Glacial charcoals. The occurrence of such concentrations within the site was observed in geomorphological trenches. Besides, this idea is confirmed by the fact that charcoals of the presumable Late Glacial chronology mostly come from samples collected in the border zone of the lower sections of archaeological features and natural layers. Such samples usually contain some amount of yellow, clayey sediment. Secondly, older charcoals could be deposited there during the usage of the features, and – thirdly – after leaving the settlement. In turn, only the last option can explain the delivery of the younger charcoals.
Consequently, it was considered reasonable to eliminate all the charcoals of trees that provided above-mentioned early and late dates, from the overall reconstruction of environmental context of the Early Neolithic settlement at Moravany (Lityńska-Zając
The series of dates obtained at Moravany, even after the above elimination procedures, is the largest one in the entire eastern Slovakia, regarding the local Early Neolithic. These dates, which by interpolation can be hypothetically considered as made exclusively on oak samples, give a compact and relatively certain chronology of
We deal with a slightly similar situations in the case of two Late Neolithic sites situated in the Upper Tisza river basin: Polgár-Csőszhalom (Raczky
The anthracological analysis from these sites were conducted in order to reconstruct woodland vegetation near Polgár settlements during the Middle Neolithic occupation (Moskal-del Hoyo, 2013; Moskal-del Hoyo and Lityńska-Zając, 2016). Taxonomical analyses revealed the presence of single charcoal fragments belonging to
Worthy of mention is the date obtained from a fragment of awns of
Ludwinowo is situated in north-central Poland, in the territory of Kuyavia. It is one of many local sites of the LBK, which is the first Neolithic unit in Central Europe. The settlement concentration of the LBK in Kuyavia is exceptional in lowland territories of Central Europe due to high number of recorded sites (
At Ludwinowo three 14C dates were obtained from taxonomically identified plant remains, which occurred in two features situated in the south-western part of the site (Mueller-Bieniek
Perhaps the most interesting is the third date, made on seeds of
These three dates from annual plants are mutually compatible,
The site at Mozgawa, in southern Poland, belongs to the Funnel Beaker culture (
So far, eleven dates were obtained from plant material found in features of the TRB at Mozgawa. One of them refers to the early Bronze Age and corroborates the operating of post-depositional processes, later than Neolithic. Other dates (Fig. 7) are congruent to each other and indicate settling of the village around 3600–3400 cal BC, and possibly, perhaps with a lesser intensity, in the later part of the fourth millennium cal BC. This perfectly corresponds to chronological characteristics of archaeological findings. In these findings, mainly in pottery, characteristics of the so-called classical phase of the south-eastern group of the TRB, placed around mid-fourth millennium cal BC, can be recorded (Włodarczak, 2006; Nowak, 2009). On the other hand, pottery with elements of the so-called Beaker-Baden assemblages, dated to the turn of the 4th and 3rd millennia BC (Zastawny, 2008, 2015), were also noticed. It is also worth noting that Beaker-Baden assemblages were discovered first and foremost in eastern part of the Western Lesser Poland less uplands (Kruk and Milisauskas, 1999: 171–215),
Among these ten dates, nine were made on annual plants, of which seven on wheat grains. One date comes from
One date was obtained from pine charcoal (Fig. 7: 2). It also correlates very well with other dates. This is not surprising, as the morphologically identified branchwood was purposefully handed for dating. As it turns out, once again, the date of charcoal not necessarily has to be too young, if made on suitably selected samples.
The case studies presented above illustrate a number of benefits flowing from the proper selection of plant material for radiocarbon dating.
The dating of annual or biannual plants makes it possible to obtain dates that usually overlap and produce a narrow time range, which correlates well with the chronology established on the basis of other, ‘reliable’ materials,
Of course, apart from information of a strictly chronological nature, dates of that kind obtained from domesticated plants reveal what species were cultivated by a given community. On the other hand, dates from shortlived wild plants or those that were not cultivated in the Neolithic can convincingly demonstrate their attribution to the Neolithic context, as for example with
The dating of plant remains representing species uncommon for the environment in which given human groups developed (here: Early and Middle Neolithic communities) and which were identified by archaeobotanical analysis often results in the dates which diverge greatly from what might be expected based on the archaeological context. Apart from providing confirmation for our assessment of what is and what is not typical for the flora of a given territory and time, such dating (reliable as it indeed is) allows us to demonstrate the operation of post-depositional processes which, be they cultural or natural, transform the original contents of anthropogenic features, introducing to them older or younger artefacts and natural substances (Schiffer, 1996). The operation of such processes should be taken into account in the case of plant remains, too. The discussed dates are one more, and very convincing, proof that anthropological features discovered on archaeological sites are not closed assemblages (also with respect to plant remains), the fact still quite often ignored by archaeologists, archaeobotanists, and scholars from other disciplines directly or indirectly interested in the human past.
The dates obtained from plants ‘atypical’ of the Neolithic, and which considerably diverge from the expected ranges, should be eliminated from the analysed cultural context. The dates that remain offer a reliable chronology, consistent with hitherto findings concerning the chronological position of particular archaeological materials. The best example of such a situation is the Moravany site.
On the other hand, the dates of the discussed type enrich our knowledge about the environmental conditions in other periods, as demonstrated in Moravany and the two sites from the Polgár quoted above.
The dating of young shoots, branchwood, and external rings brings similar results,
The chronology of ‘short-lived’ wood correlates with radiocarbon chronology based on materials other than wood, where such materials are available (
The examples presented above, along with their discussion, clearly indicate that a number of factors need to be considered when selecting samples for radiocarbon dating. First of all, one should bear in mind that “radiocarbon laboratory dates the sample we submit, not the feature we want to date with that sample” (Lityńska-Zając and Wasylikowa, 2005: 59). Therefore, the connection of the analysed sample with a feature and layer should be each time determined, and possible contaminations eliminated.
It is best to date single, “large” specimens, known as plant macroremains, such as fruits, seeds, buds, leaves, and other vegetative parts (Wasylikowa, 1986), including also those of wild plants. For obvious reasons, the dates obtained from the remains of annual or biannual plants, whose lifespan is limited to one or two vegetative seasons, are closest to reality. They give a compact period of time, usually narrower than the chronology based on charred wood fragments, and consistent with chronological suggestions based on pottery, chipped lithics, stone artefacts,
The situation is different in the case of long-lived organisms such as trees. As regards charcoal, fragments determined as twigs, branches, and external rings should mainly be taken into account, while those belonging to long-lived elements of trees should be avoided. Then it turns out that such dating does not differ in terms of precision from the dating obtained from other materials.
These dates, as well as the above-mentioned dates of fruits and seeds allow for the rejection of some of the dates made on undetermined charcoals, usually the earliest ones in a given situation.
The presence of unexpected taxa from the perspective of the history of local flora and cultivation practices may indicate some taphonomic and stratigraphic problems. These taxa illustrate the significance of the detailed botanical identification, since plant materials of the Neolithic age include only a limited number of cultivated species and typically do not contain remains of late arrived and late used plants. In other words, there is a big risk of getting dates later than the Neolithic. But such dates are also valuable. They are important for the history of local vegetation, and demonstrate the operation of a variety of cultural and natural post-depositional processes within a given archaeological site.
To finally recapitulate, our contribution emphasises the necessity of taxonomical identification of plant remains prior to radiocarbon dating as a measure for choosing the most relevant materials. The most appropriate specimens should be selected using the knowledge about plants typical for each chronological period in a given region, including wild and cultivated ones. If we want to properly date a feature or a site, and not only the sample, then we have to choose what is the most typical for specified time and place.