Union Académique Internationale

Project nº92, adopted in 2017

Since the origins of prehistoric research, variations in climate and its influences on the peopling of the early humanities have appeared to the pioneers of prehistoric archaeology as the proof of the earliest age of humanity. Edouard Lartet discovered in 1864 during his excavations of the rock-shelter of La Madeleine in Perigord, a mammoth engraved on a fragment of ivory tusk of mammoth. It thus demonstrates the cohabitation of the human species with an extinct species living under a glacial climate. At the end of the 19th century, discoveries of cold and warm faunas have multiplied, showing that humanity had to successfully cope with significant climate changes revealing the alternation of glacial and interglacial periods. At the beginning of the 20th century, the glaciology work of Penck and Brückner on the remains of glacier front moraines in the Alps, highlight for the first time the succession of ice ages called Würm, Riss, Mindel, Gunz. The research extends to rivers, which, due to alternating climates, by siltation or over-digging, create valleys with terraces, thus proving the very old age of the discoveries of Casimir Picard and Boucher de Perthes in the Somme Valley between 1830 and 1860.

It is not surprising, then, that prehistorians became the first paleoclimatologists in the history of science. The spectacular cores in the inlandsis of Greenland and the Antarctic continent should not overshadow the many other methods of climate reconstruction, which allow the computation of palaeo-temperature curves, palaeo-precipitation curves or other curves: sequences of lœss and fossil soils (on the periphery of ice sheets), sand sequences and fossil soils (in desert areas), oceanic and Mediterranean cores (from the inventory of mineral-skeletal species, such as foraminifera or coccolithoforids, particularly sensitive to changes in ocean temperature), stratigraphic sequences of rock-shelters and caves, cores in volcanic lake sediments (maar), in mountain lakes, in marshes (bogs) to extract pollen, altitudes of fossil shore lines, travertin, speleothems, coral reefs, etc.

Modern palaeoclimatology was born in the 1970s, with the multiplication of deep cores. This new science is multidisciplinary using deep core engineering (from the oil industry), sampling (air bubbles, pollens, fossils, etc.), fossil species determinations, isotopic measurements (for the O18/O16 curve), magnetic susceptibility measurements, geochemical measurements (oxygen, nitrogen and CO2 of air bubbles), absolute dating (to synchronize sequences), signal processing (to compare curves obtained having differential sedimentation and gaps), statistical treatments (to calculate transfer functions), mathematical modeling (atmospheric circulation model, climate transition model, etc.).

For hunter-gatherers, during the last million years of the Pleistocene, the peopling in a geographical region, the location of archaeological sites, the territory of traveling of human groups, the food resource management during the annual cycle, the material culture (lithic industry, bone, ivory and deer wood industry), figurative animal art (as in the Sahara), the crossing or not of passes and straits, are all information that helps to highlight the adaptation of human groups to climate changes.

For farmers/breeders, the climatic variations of the last twelve thousand years of the Holocene were numerous: hot and humid early Holocene, 8200 BP cold event, 4200 BP arid event, 2400 BP arid event, optimum of the Roman empire (200 BC – 400 AC), medieval climatic optimum (10th-12th century), small ice age (13th - 19th century). These variations had considerable consequences for sedentary agro-pastoral societies: desertification of the Sahara, emigration from the Middle East and neolithization of Europe, abandonment of agriculture for pastoralism, landscaping for irrigation (Nile reservoirs, irrigation canals in Central Asia and Mesopotamia, drainage of deltas, terraces of mountain slopes, etc.). The need for such a community work is probably at the origin of the first state ownership of societies. But these still fragile structures were also victims of cold and arid episodes that caused collapse as for the 8200 BP and 4200 BP episodes.

It is the studies of the relationship between human societies from the origins to the early historical times that are the subject of the project that the UISPP proposed to the UAI.