Abstract

The late Middle Pleistocene period is characterized by significant climatic fluctuations, alternating between glacial conditions (ice ages) and interglacial periods similar to the present day. Four distinct interglacials are apparent within the British late Middle Pleistocene geological record; early human populations were able to colonize Britain during three of these temperate periods, but were conspicuously absent during the most recent, the Ipswichian interglacial.

The deposits preserved in the famous gravel pits around Swanscombe, Kent, have yielded some of the most important evidence for hominin occupation during the Hoxnian interglacial (~440 ka), the temperate period that immediately followed the major Anglian glaciation. The site is most notable for the discovery of a human skull, a rarity within the British Palaeolithic record. Furthermore, two distinct assemblages of stone tools suggest that separate groups of early humans colonized the Thames valley.

The fossiliferous sediments at Swanscombe have preserved rich molluscan and vertebrate assemblages which allow reconstructions of the prevailing climatic and environmental conditions. They also allow inferences about sea level and palaeogeography to be made. An important element of the molluscan succession at Swanscombe is the so-called ‘Rhenish suite’ of aquatic snails, now found in central and southern Europe, which suggest that the Thames was confluent with continental rivers during the early part of the interglacial. The onset of estuarine conditions in the Lower Thames, implying a rise in sea-level in the North Sea, is indicated by the appearance of ostracod and fish species that inhabit brackish water.

These data have important implications for understanding the palaeoenvironmental conditions under which humans were able to colonized Britain and northwest Europe.