Excavations of Derragh island in 2004 and 2005 under the Lake Settlement Project uncovered a layer of hazelnut shells preserved by the waterlogging of the site. These shells were comprehensively sampled but were then stored for the intervening years. They have now seen the light again and been subject to a recent study aimed at deciphering the reasons for their deposition as well as studying what the shells themselves can tell us about the Mesolithic hazelnut economy.

Once washed of the peat matrix that had kept them preserved for the past 6000 years the shells were broadly categorised into three groups: whole hazelnuts; hazelnut shells that represent half a longitudinally split hazelnut; and chips of hazelnut shells. The group comprising half shells was by far the largest and these, along with the whole hazelnuts, were measured for comparison with other assemblages and modern material. It was also noted that the chips had likely come from broken halved hazelnuts since very few fragments comprised either the complete top or bottom of the shell or would have straddled the split.

Small patches and the discolouration of light charring were noted on all shells, this is in contrast to other archaeological hazelnut shell assemblages which have been heavily charred. Charring preserves shells however the need to be charred in order to survive leads to significant taphonomic biases. The waterlogging of the Derragh hazelnuts therefore preserved nuts which may not otherwise have survived and gives a much fuller picture as to the Mesolithic treatment of hazelnuts which were a valuable source of energy over the winter months.

Hazelnuts are traditionally tricky to remove from their hard shells and most archaeological hazelnut shells are found as small fragments from where the nuts have been smashed, usually between two stones to shatter the shell. The excellent condition of the Derragh shells, the large size of the shell chips, the predominance of half shells, and the existence of a certain percentage of whole hazelnuts led to the suggestion that these hazelnuts had been sprouted. Sprouting splits the shell longitudinally as the kernel grows out.

Measurements confirmed that the whole hazelnuts were typically the irregularly shaped nuts or the smaller nuts. If the nuts had been sprouted their exclusion may have been due to immaturity, deformation or simply being blind and containing no kernel to sprout and would have been immediately identifiable. However, they may also have been the ones least likely to be selected during manual hazelnut shell breaking.

The presence of light charring suggests that at some point, probably after sprouting, the nuts were roasted. This heat would have killed off the germination of the nut and left it within the jaws of the shell which could then have been easily prised apart without resorting to hitting with stones. This task requires little more than fingernails and could easily have been carried out by the otherwise less able members of the group. It also leaves the kernel intact and the shells tidy, especially as compared to the process of bashing shells with stones whereby the kernels and sharp shell fragments are liable to fly off and become lost. When compared to individually opening the shells between stones, prising apart sprouted shells is also significantly quicker.

There is also a possibility that this 'malting' may have contributed to the taste and storage capabilities of the nuts. Light roasting is known to extend the lifespan of a hazelnut into springtime and improve the flavour. But these hazelnuts could have been allowed to dry out during winter storage and then restored during the germination process, extending their usability well past spring. The taste is little affected, whereas dried nuts are unpleasant to the point of being inedible, 'malted' hazelnuts have a smooth, rich flavour and could have been eaten whole or used in cooking. Malted grains also hold an important part in modern life in that they are essential in the brewing process.

Finally, the deposition of the shells within the layer where the curving surface of the nut was upwards may have seen the shells taking on another role, that of constructional material within the Derragh Island Mesolithic platform site.