as the Upper Palaeolithic in Europe circa 35,000 BCE, and may be the earliest proto-writing: several symbols were used in combination as a way to convey seasonal behavioural information about hunted animals. Lines (|) and dots (•) were apparently used interchangeably to denote lunar months, while the (Y) sign apparently signified "To give birth". These characters were seemingly combined to convey the breeding period of hunted animals. Changes in climate and geography The climate of the period in Europe saw dramatic changes, and included the Last Glacial Maximum, the coldest phase of the last glacial period, which lasted from about 26.5 to 19 kya, being coldest at the end, before relatively rapid warming (all dates vary somewhat for different areas, and in different studies). During the Maximum, most of Northern Europe was covered by an ice-sheet, forcing human populations into the areas known as Last Glacial Maximum refugia, including modern Italy and the Balkans, parts of the Iberian Peninsula and areas around the Black Sea. This period saw cultures such as the Solutrean in France and Spain. Human life may have continued on top of the ice sheet, but we know next to nothing about it, and very little about the human life that preceded the European glaciers. In the early part of the period, up to about 30 kya, the Mousterian Pluvial made northern Africa, including the Sahara, well-watered and with lower temperatures than today; after the end of the Pluvial the Sahara became arid. The Last Glacial Maximum was followed by the Allerød oscillation, a warm and moist global interstadial that occurred around 13.5 to 13.8 kya. Then there was a very rapid onset, perhaps within as little as a decade, of the cold and dry Younger Dryas climate period, giving sub-arctic conditions to much of northern Europe. The Preboreal rise in temperatures also began sharply around 10.3 kya, and by its end around 9.0 kya had brought temperatures nearly to present day levels, although the climate was wetter. This period saw the Upper Paleolithic give way to the start of the following Mesolithic cultural period. As the glaciers receded sea levels rose; the English Channel, Irish Sea and North Sea were land at this time, and the Black Sea a fresh-water lake. In particular the Atlantic coastline was initially far out to sea in modern terms in most areas, though the Mediterranean coastline has retreated far less,