7 Discussion and conclusions
7.1 Mortuary variabilitynext section
A rough division can be made in three groups as far as the depositions of the human skeletal remains are concerned: inhumation graves, cremation remains in settlement context and scattered human bones. The inhumation graves show diversity in the disposal of the dead. There were single, double and multiple inhumation graves and the remains were either complete or incomplete.
From the Mesolithic period burials are scarce and appear to have been either isolated or in small burial grounds for instance at Vedbæk and Skateholm in Scandinavia, at Téviec and Hoëdic in Brittany (Albrethsen & Brinch Petersen 1976; Larsson 1990; Péquart & Péquart 1929, 1934, 1954; Péquart et al. 1937). The most frequent burial posture is supine with stretched limbs. Burials in which the deceased was buried in a sitting position, like one burial at De Bruin, are also attested at several other European sites, Bäckaskog in Skåne and Lummulunda on the isle of Gotland, Sweden (Stenberger 1962, 36; Newell & Constandse Westermann 1979). We may deduce that the observed traditions seem to be in accordance with those in northwest Europe for the late Mesolithic period. At Swifterbant and Urk the same burial posture is attested.
A change from a stretched to a position on the side with flexed limbs evidently took place before or around c. 3500 BC. This phenomenon is known from several burials associated with the Michelsberg culture in the south (Ilett & Coudart 1983). Stable isotope analysis has shown that two individuals from Schipluiden probably originate from other areas including the southern regions. This indicates either migration and/or other contacts. Liaisons with these people may have been at the root of new traditions including the treatment of the dead.
Most sites have yielded scattered, unarticulated, human bones and bone fragments as well as formal burials. These remains can indicate a variety of processes and actions. They can be the result of taphonomic processes, related to an archaeologically invisible above-ground treatment of the dead for which again many options exist. One is a mortuary ritual like excarnation in the open, on a platform. After a certain period the bodies are decomposed or defleshed and (secondarily) buried or discarded. Secondly, there may have been fighting between members of the group or with outsiders, leading to discarding of the remains of slain enemies, to trophy hunting, or even cannibalism. Thirdly, an unnatural death or mysterious disease can also lead to a different manner of handling the body resulting in the observed spectrum. Furthermore postdepositional disturbances of formal burials can cause the dispersion of bones as well.
There are several restrictions in reconstructing the composition of prehistoric populations on the basis of the present evidence. First of all there is the question of representativeness of the human remains for the population at large. The demographic investigation is frustrated by the apparent different treatment of young children and infants, and especially by the archaeologically elusive above-ground treatment of the dead. Postdepositional processes like preservation circumstances have caused loss of bone material as well. The scattered bones, moreover, offer limited opportunities for sex and age diagnosis, so a large part of the groups of individuals concerned remains unspecified.
Demographic studies are often directed at the establishment of the growth rate of populations – were they stable, declining or growing – in spite of the fact that age distributions of skeletons are often biased. A rise in the percentage of subadults between 5 and 19 years from c. 20 to 30%, as based on skeletal evidence for 68 European Mesolithic and Neolithic populations, would indicate population growth for the early Neolithic period (Bocquet-Appel & Dubouloz 2004). Jackes et al. (2008) argue for a stable Mesolithic population and a growing Neolithic one based on the fertility parameters of the populations of among others Lepenski Vir and Vlasac in the Ðerdap/Iron Gates gorge in south-east Europe. In view of the general background the data at our disposal from the populations in the Lower Rhine Basin are presented in table 6 in reference to other European Mesolithic and Neolithic series. This table is condensed after Bocquet-Appel (2002) and adapted using data from Jackes et al. (2008) and our populations from the Lower Rhine Basin.
Generally the Neolithic skeletal series display a higher proportion of juveniles between 5-19 years (based on the table published by Bocquet-Appel 2002). The values presented in table 6 show a mean ratio for the immature individuals of 0.189 (sd = 0.061) for the Mesolithic and 2.214 (sd = 0.078) for the Neolithic groups. The series of Hardinxveld-Giessendam and Swifterbant/Urk show a low proportion of immatures, with values well below 0.2. This could be indicative of a declining population, but these cases probably display biased distributions. These data are therefore interpreted as not representative of the underlying groups, but they are a welcome basis for the (qualitative) assessment of the group composition. The pooled data for Ypenburg and Schipluiden on the other hand show a proportion of juveniles of 0.267, which is well above average in comparison with other Neolithic groups. The mortality for the age interval 0-4 years is considerable as well at c.21%. We can conclude that these data are representative for the population at large and tentatively indicate population growth.
Table 6 Demographic parameters of Mesolithic and Neolithic populations (data partly derived from Bocquet-Appel 2002).
The skeletal remains from the Ypenburg population are the most informative on the topic of health in comparison to the other groups in the Lower Rhine Basin. The pathological traits show a variety, of which degeneration of the joints and the spine is the most common. This can be related to a sedentary lifestyle and physical labour (Baetsen 2002).
For comparison the information on stature of various Mesolithic and Neolithic groups is presented in table 7 (after Formicola & Gianecchini 1999). The values of the Ypenburg population are comparable to those of Skateholm, Téviec and Hoëdic. The data from Hardinxveld-Giessendam and Schipluiden resemble those of Bandkeramik farmers. Although data are sparse we can deduce that the stature at Ypenburg was rather low compared to several other Mesolithic and Neolithic European groups (table 7). Conclusions on the health status of the populations of Hardinxveld, Swifterbant and Schipluiden cannot be made due to the restricted data. There are, however, several indications of the health of the Ypenburg population to be able to draw tentative conclusions. These are a rather high infant mortality, low stature, and skeletal markers of physical stress. Although fertility was indicative of a growing population this leads us to question whether living conditions were as favourable, as has been suggested by the zooarchaeologists (De Vries in Koot et al. 2008).
Table 7 Stature of Mesolithic and Neolithic populations (data partly derived from Formicola & Giannecchini 1999).
As strontium values are bound to geological formations the results can be less distinctive as we would like because the underground formations of a region can be quite homogeneous. Multiple isotope analyses of additional elements like – especially – oxygen improves the possibility to discriminate between locals and non-locals. This is illustrated by one immigrant at Swifterbant, which shows deviant Sr but local O values and two individuals at Schipluiden with normal Sr but deviant O values. Lead isotope analyses are in accordance with these findings and therefore strengthen the interpretation.
The combination of the various isotope studies on provenance and diet offer the possibility to elucidate inter-individual variety in diet as well. This is shown by the fact that some of the immigrants displayed a diet lower in fish. When relating these observations to the burial ritual it appears that all the people in the graves at Schipluiden were of local origin, and that both immigrants are represented by isolated molars only, bearing witness to an above-ground treatment of the dead. Differences with respect to gender cannot be studied as females are underrepresented in Schipluiden. A future isotope study of the Ypenburg population would be desirable and a valuable addition to this topic.
The Mesolithic samples show a distinct aquatic component, but the diet seems to have been mixed and rather complex, perhaps to be associated with a variable habitation regime throughout the year, the river area in winter and (possibly) the higher areas at other times of the year. Mesolithic diets in Denmark also display a complex nature with a terrestrial and aquatic component (Richards et al. 2003b). In the Meuse valley the Mesolithic diet was mixed with a major terrestrial signature (Bocherens et al. 2007).
The population of Swifterbant had a diet with a larger proportion of protein from terrestrial sources, but also with an aquatic element. The 13C values are comparable with the Mesolithic samples but the 15N values are more modest. The utilization of local food sources, both aquatic and terrestrial in nature, is not fully in agreement with the environment and may point to a similar seasonal exploitation of upland territory as the Late Mesolithic Hardinxveld series.
The coastal situation of Schipluiden, near the estuary of the Meuse, favoured the consumption of marine food. This is evident from the isotope values as well. Both 13C and especially 15N are indicative of a largely marine/aquatic diet. The presence of sturgeon may have been important in this case.
The high proportion of marine and aquatic protein in the diet of the Schipluiden people is in line with the archaeozoological evidence, showing that these people practised an ‘extended broad spectrum economy’, combining the traditional exploitation of a wide range of natural resources with the ‘new’ crop farming and animal husbandry, but estuarine fishing must have been of far greater importance than reflected in the recovered remains. The residues from food vessels at Schipluiden confirm this conclusion as having contained aquatic food. The results of Schipluiden are comparable to those of the two millennia older Iron Gates gorge sites of Lepenski Vir and Vlasac, where the consumption of sturgeon and fish roe probably played an important role in the diet as well (Fig. 14; Bonsall et al. 1997, 2000; Borić et al. 2004). The data derived from the Danish and Portugese Mesolithic and Neolithic sites show a clear change in time in favour of terrestrial food sources (Richards et al. 2003b; Lubell et al.1994). The N values are lower compared to our populations of the Lower Rhine Basin indicating the consumption of food from sources that held a lower position in the food chain.
This demonstrates that Neolithisation was still in an initial stage as far as diet is concerned even as late as 3500 BC, almost two millennia after agriculture was introduced by the Bandkeramik farmers in the loess zone of the Rhineland, Limburg and Belgium, less than 200 km to the south.
Fig. 14 Stable isotope ratios δ13C and δ 15N for human bones from Hardinxveld, Schipluiden and Swifterbant (cf. figure 11) compared to those from the Iron Gate sites Lepenski Vir, Vlasac and Schela Cladovei, from Portugal (after Lubell et al. 1994), and from Denmark (after Richards et al. 2003b).
The richness in aquatic food sources present in the Lower Rhine Basin shows up in the isotopic signature of the populations studied. The composition of the diet with respect to proteins seems to be highly related to the exploitation of the natural surroundings, more than on the available knowledge of food production. Some outsiders display a more terrestrial diet, which is understandable when they originated from other regions with other resources, but some locally born and grown people had a more terrestrial diet. One can think in those cases of a special social position, food taboos or personal tastes which led to a diet lower in fish.