Geology and archaeology: submerged landscapes of the continental shelf: an introduction

Sea-level change has influenced human populations globally since prehistoric times. Even in early phases of cultural development, human populations were faced with marine regression and transgression associated with the glacial–interglacial climatic cycle, amplified by glacio-isostatic adjustments in some regions. Global marine regression during the last glaciation changed the palaeogeography of the continental shelf, converting former marine environments to attractive terrestrial habitats for prehistoric human occupation, and adding an extensive new increment of land, in the case of Europe amounting to an additional 40% of the existing land area, and on a global scale to some 20 million km of additional territory that is now submerged. These areas of the shelf were used as hunting and gathering areas, and as pathways of dispersal between regions and between continents, until they were resubmerged by the post-glacial marine transgression. They also most probably witnessed the earliest developments in seafaring, marine exploitation and permanent settlements. Based on modern marine research technologies and the integration of large databases, proxy data are now becoming available for the reconstruction of these submerged Quaternary landscapes. Concerted efforts are also now being devoted to the search for prehistoric archaeological sites and artefacts on the seabed, often in collaboration with marine scientists. This search has been stimulated by the increasing amount of material that has demonstrably survived inundation, often with excellent preservation of organic remains, by closer collaboration with offshore industry, and by the growing realization of the importance of these submerged data for understanding human prehistoric developments during periods of rapidly changing climate and environment. Moreover, these new research trends are not simply being driven by an archaeological need for scientific and technological input from other disciplines, but by collaborations involving genuine mutual benefit, in which all partners have something to gain. Archaeological problems often pose new questions about geological change, stimulating new techniques of observation, new technologies and new investigations, which in their turn can offer new data, often at higher resolution and with better dates, in relation to geological and environmental issues such as sea-level change and palaeoclimatic variability on the continental shelf. The expansion of early human populations to occupy new territory and new continents is one of the great narratives of human evolution. It is currently a theme of wide interest and topicality, and has received significant impetus and publicity from the new science of palaeogenetics. Together with ongoing discoveries of new fossil and archaeological material, and new studies of palaeoclimate and palaeoenvironment, the field itself is rapidly expanding, leading to new discoveries and new controversies (Grine et al. 2009; Gamble 2013; Smith & Ahern 2013). All the current indications are that the human species originated in Africa, with at least two major episodes of dispersal. The earliest, some time after about 2 myr ago, led to the expansion of Homo ergaster/erectus populations across southern Europe and Asia, extending from Britain in the west to China and Indonesia in the east and south. The second involved our own species, Homo sapiens (Anatomically Modern Humans or AMH), and took place some time after about 200 ka. This resulted in the replacement of earlier hominin populations in Europe and Asia, and expansion further afield: into New Guinea and Australia, certainly involving sea crossings over distances of at least 50 km, by about 50 ka; to the higher latitudes of northern Eurasia, with entry into the Americas by at least 15 ka; and into new territory exposed by the melting of the northern hemisphere ice sheets less than 10 kyr ago. Anthropological and archaeological investigations of these processes are directly connected