ImageNo, not some new dieting fad – what beetles, lentils and anchovies have in common is their value as indicators of ancient climate change. In a special issue of the journal Fisheries Research (Volume 87, November 2007), an international group of ecologists and historians have drawn upon archaeological material, tax accounts, church registers and monastic account books to present a picture of marine life in the North Sea from 7000 BC to the present.

They found that warm-water species, including anchovy and black sea bream, once thrived around Britain’s shores – notably during the warm Atlantic period that lasted from around 7000 to 3900 BC. When this warm period ended, these species rapidly disappeared from the archaeological record.

More recently, archival records from fishing communities around the North Sea indicate that the ‘Little Ice Age’, which lasted from the 16th century to the mid 19th century, had two sub-periods of particularly severe cold – 1675-1683 and 1685-1696 – when herring spawned later in the year, so that the fishing seasons started later and were shorter in duration, with substantially lower catches.

During this same mini Ice Age, nettle bugs (Heterogaster urticae), so named because they feed on stinging nettles, were absent from the North of England, whereas prior to this they are commonly found in archaeological deposits dating from the Roman and Anglo-Scandinavian periods in York. Harry Kenward, writing in The Archaeologist, says that they have become very common again in Yorkshire since 1990, after a gap of four centuries, and are now heading in the direction of Scotland.

Chris Stevens, of Wessex Archaeology, also reveals in The Archaeologist (Winter 2007) that lentils are not just the staple of recent vegetarian diets, but have been cultivated in the UK whenever their favoured growing conditions – warm summers and mild winters – have permitted. Their presence in the archaeological record in the form of charred remains at rural sites in southern, eastern and central England correlates pretty precisely to the presence of nettle bugs in the north, indicating periods of climatic warming in the period AD 800 to 1350, peaking towards the end of the 10th century, and their absence after 1300.

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