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Natural History Museum, Cromwell Road, London SW7 5BD, UK
During the Middle-Late Quaternary the British Isles have alternately been part of the Continent of Europe and separated from it by the sea. Comparison of mammalian faunas from sites on both sides of the present English Channel can contribute to the reconstruction of Britain’s island history. The most suitable chronological framework for this study is discussed. Attention is drawn to problems of applying the 1973 scheme of the Geological Society of London, which is used here only in conjunction with the more straightforward chronology of the deep-sea oxygen isotope record. Special attention is directed to events during the period of time c. 250 000 to 30 000 years BP. The chalk land-bridge that had previously joined the British Isles to the Continent of Europe had by this time been breached, and any further changes in the land connection are likely to have been the result of eustatic changes of sea-level, associated with glacial-interglacial fluctuations of climate.
Whether the British Isles became isolated from the Continent during the high sea-level phase that occurred during isotope stage 7 is uncertain from the mammalian evidence. The occurrence of human artefacts and remains of pond tortoise Emys orbicularis, which is unlikely to have tolerated salt-water, in deposits representing the earliest part of this stage, suggests a land connection then or not very long previously. Human presence continues into isotope stage 6, characterized also by the arrival of steppe rodents from eastern Europe; evidence of a further episode of low sea-level.
During the Last Interglacial, oxygen isotope stage 5e, sea-level rose once more, isolating the British Isles from the Continent. Remarkably, humans, horses and the mollusc Corbicula fluminalis, so common previously, fail to reappear, a consequence, perhaps, of being cut off by rapidly rising sea-level at the end of stage 6. A very characteristic fauna, including hippopotamus, straight-tusked elephant, narrow-nosed rhinoceros, fallow deer and abundant carnivores, did nevertheless manage to become established throughout England and Wales at this time, some as far north as Durham.
Falling sea-level associated with the Devensian (isotope stages 5d-2) re-established the land connection. Hippopotamus had by this time disappeared and been replaced with a fauna including woolly mammoth, woolly rhinoceros and reindeer. Humans and horses returned once more. It was not until sea-level rose again during the Holocene that the British Isles became finally isolated from the Continent, as they are today.
