The ages of the modern cockle collections were plotted on the line graphs shown below in Figure 11. There are distinct differences between the commercially exploited population from Wales and the unexploited population from Scotland. The graphs for Lincolnshire and Essex show cockle populations at different stages of recovery after a depletion caused by commercial over exploitation.
Figure 11: Modern cockle collection age classes
Top left: Wales commercially exploited population
Top right: Scotland undisturbed wild population
Bottom left: Essex recovering population after 2 years' suspension of collection
Bottom right: Lincolnshire recovering population after 1 year's suspension of collection.
The following results were obtained when the archaeological cockles were plotted against the modern age class curves.
Figure 12: Krabbesholm 7737 age classes plotted against the modern Welsh and Scottish age curves 
Top left: Pocket 6a
Top right: Layer 7
Middle left: Layer 8
Middle right: Layer 10
Bottom: Layer 15
Few of the age curves in Krabbesholm 7737 closely resemble the modern cockle curves. The closest match to the modern undisturbed curve is in layer 15, although this has a peak in age class 5 which may indicate a preferential collection of larger cockles from an essentially undisturbed population. Table 3 presents a summary of the collection patterns from Krabbesholm 7737.
Figure 13: Krabbesholm 7738 age classes plotted against the modern Welsh and Scottish age curves
Top left: Layer 2
Top right: Layer 4
Middle left: Layer 10
Middle right: Layer 12
Bottom Layer 13
The curves from the Krabbesholm 7738 most closely resemble the modern recovering and commercially exploited age curves, which could indicate an intensifying of anthropogenic exploitation of this resource at this site in the late Early and Middle Neolithic. A summary is shown in Table 3.
Table 3: Summary of the Krabbesholm cockle collection patterns demonstrated by age range
| Krabbesholm 7737 | Krabbesholm 7738 | ||
|---|---|---|---|
| Layer | Type of modern age curve closest to the archaeological age curve | Layer | Type of modern age curve closest to the archaeological age curve |
| 6a | Commercially exploited | 2 | Recovering |
| 7 | Commercially exploited/undisturbed | 4 | Recovering |
| 7 | Commercially exploited/recovering | 10 | Commercially exploited |
| 10 | Commercially exploited/recovering | 12 | Commercially exploited/undisturbed |
| 15 | undisturbed | 13 | Commercially exploited |
The Norsminde age curves as plotted against the modern curves show an interesting pattern, especially the two Mesolithic layers, which are closer to the modern commercial curve than the unexploited modern curve. The later Mesolithic curves are much more akin to the modern undisturbed population curve and this raises some interesting questions regarding the intensity of cockle exploitation in the earlier Mesolithic at this site (see Figure 14).
Figure 14: Norsminde age classes plotted against the modern Welsh and Scottish age curves
Top row 1 left: Layer 1
Top row 1 right: Layer 2
Row 2 left: Layer 3
Row 2 right: Layer 4
Row 3 left: Layer 5
Row 3 right: Layer 6
Row 4 left: Layer 7
Row 4 right: Layer 8
Row 5 left: Layer 9
Row 5 right: Layer 10
All the Neolithic curves at Norsminde are closer to the modern commercially exploited or recovering population age curves. A summary is shown in Table 4.
Table 4: Summary of the Norsminde archaeological cockle collection patterns demonstrated by cockle age
| Neolithic | Mesolithic | ||
|---|---|---|---|
| Level | Type of modern curve closest to the archaeological age curve | Level | Type of modern curve closest to the archaeological age curve |
| 1 | Commercially exploited but returning to unexploited | 7 | Unexploited |
| 2 | Commercially exploited | 8 | Unexploited |
| 3 | Recovering population | 9 | Most akin to commercially exploited |
| 4 | Commercially exploited | 10 | Most akin to commercially exploited |
| 5 | Between commercially exploited and unexploited | ||
| 6 | Between commercially exploited and unexploited | ||
The cockles in the lower Mesolithic layers at Norsminde were expected to display age curves most similar to the unexploited modern age curve and the two latest Mesolithic layers, 8 and 7, do so. However the two earliest Mesolithic layers, 10 and 9, are much more like the modern commercially exploited curve. This may indicate a natural cockle population crash caused by local environmental change or could be a sign of intensive human exploitation. Layers 8 and 7 appear to indicate a stable cockle population under no undue environmental stress and on which human collection made no significant impact. What is really interesting is the changing pattern in the Neolithic layers to a profile more indicative of intensive exploitation (by analogy with the modern curves), which suggests a degree of intensification of gathering, or some environmental change.
The evidence from Krabbesholm is more difficult to interpret. This may reflect the smaller sample sizes and the lack of whole cockle valves in many of the layers. There is no cockle age data for the Mesolithic layer at this site. Of the Neolithic layers where there are sufficient valves, the age curve patterns are closer to the modern commercially exploited population, especially in the later layers.
In sum there appears to have been an intensification of cockle collection in the Neolithic which does not sit well with the isotopic research on human bones from that period, which appears to indicate that marine foods were more or less abandoned in favour of terrestrial resources (Tauber 1981; Lubell et al. 1994; Richards et al. 2003a), although this evidence is disputed by several archaeologists (Milner et al. 2004).
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Last updated: Tues Oct 2 2007