The Late Ice Age

The Late Ice Age World (50¸000 to 15¸000 years ago)

For most of the past 45¸000 years¸ the world was very different from that of today. At the height of the Ice Age glaciation¸ some 18¸000¸ vast ice sheets mantled Scandinavia and the Alps¸ leaving a chilly corridor of open tundra between them. Sea levels were more than 300 feet (90 meters) lower than today. Britain was joined the European continent¸ the North Sea was under ice¸ and the Baltic Sea did not exist. One could walk from Turkey to Bulgaria dry–shod. Vast¸ treeless plains stretched north and east from central Europe to the frontiers of Serbia and beyond¸ a landscape of rolling scrub country dissected by occasional broad river valleys. The only signs of life were occasional large herds of big–game animals like the mammoth¸ bison¸ and reindeer¸ and they were often confined to river valleys. For humans to survive in these exposed landscapes required and layered¸ tailored clothing that could keep people warm in sub–zero temperatures.

In more temperate and tropical latitudes¸ the effects of the last glaciation are harder to detect in geological strata. Tropical regions were often drier¸ many rain forests shrank¸ and there were more open grasslands and woodlands. In Africa¸ the Sahara Desert was as dry as¸ if not drier than¸ today¸ as cold polar air flowed south of the Mediterranean. Much lower sea levels exposed enormous areas of continental shelf in Southeast Asia. Many offshore islands became part of the Asian mainland. Great rivers meandered over what were then exposed coastal plains¸ across another sunken Ice Age continent known to scholars as Sunda. Offshore lay two large land masses–Wallacea¸ made up of the present islands of Sulawesi and Timor¸ and Sahul¸ a combination of New Guinea¸ Australia¸ and the low–lying and now flooded shelf between them.

Science

Radiocabon Method

Radiocarbon method is the primary method used between 40,000 years ago and the past 2000 years. The method is based on the knowledge that living organisms build up their own organic matter by photosynthesis and by using atmospheric carbon dioxide. The percentage of radiocarbon in the organism is equal to that in the atmosphere. When the organism dies¸ the carbon 14 (14C) atoms disintegrate at a known rate¸ with a half–life of 5730 years. It is possible then to calculate the dates of an organic object by measuring the amount of 14C left in the sample. The initial quality in the sample is low¸ therefore the limit of detectibility is soon reached¸ so the oldest reliable radiocarbon dates are about 40,000 years old.

Radiocarbon dates can be obtained from many types of organic material¸ including charcoal¸ shell¸ wood¸ and hair. The beta particle decay rate is conventionally measured with a proportional counter¸ but the use of accelerator mass spectrometry has refined the procedure dramatically. Every radiocarbon date arrives with a statistical error¸ a standard deviation. For example¸ a date of 2000 (+ -) 200 years¸ that the date has a probable range of 200 years¸ a two out of three chance that the date lies between the span of one standard deviation (2400 years and 2000 years). Unfortunately¸ the concentration of radiocarbon in the atmosphere has varied considerably over time¸ as a result of alterations in solar activity and changes in the strength of the earth´s magnetic field. It is possible to correct dates by calibrating them against dates from tree rings¸ by radiocarbon date rings and developing a master correction curve. Dates as far back as nearly 9000B.C.E. can be calibrated with tree rings¸ with coral growth rings from tropical seas.