Prologue
Eugene Dubois was a Dutchman obsessed with the ”Missing Link“¸ the mythical human that was the evolutionary connection between apes and modern people. A surgeon by profession¸ in 1887¸ young Dubois even wangled a posting as an army physician to distant Sumatra in south–east Asia¸ where¸ he was convinced¸ the Missing Link would be found¸ incredible though it may seem¸ Dubois actually found what he claimed was such as ancestor on nearby Java in 1891. Digging into fossil–rich ash and river sediments as Trinil on the Solo River in northeastern Java¸ he found not only the bones of extinct animals but a human tooth¸ a thick–walled skull¸ and a human thigh bone.
Dubois was ecstatic and named his fossil Pithecanthropus erectus¸ ”ape–human which stood upright.“ This¸ he claimed¸ was the missing link between apes and humans¸ a very primitive human being. On his return to Europe in 1895¸ he was greeted with skepticism¸ then scorn. Dubois's reaction was to withdraw from the scientific arena. He is said to have kept his fossils under his bed. Modern science has vindicated Eugene Dubois¸ for he was the first to discover what is now known as Homo erectus¸ a direct ancestor of modern humanity.
THE FIRST HUMANS
Anthropologists now have evidence that the first humans appeared on the earth approximately 2,000,000 years ago. Probably the men and women who made the gigantic leap from animal to human existence lived in Africa, evolving from hominids that walked erect and learned to share food with one another. In 1995 C. E., scholars in Africa announced their latest find of bipedal hominid, Australopithecus anamnesis, which pushed back the evolutionary record even father than had previously been determined.
However, Asian origins for humanity are also possible, for researchers in China and Indonesia recently discovered skull fragments almost as old as those in Africa. No agreement among scientists yet exists on whether the first people appeared only once in a single place or whether humans appeared in different parts of Africa and Asia about the same time.
Ice Age Background
The Pleistocene began about 1.8 million years ago, after an intensification of glaciation worldwide about 2.5 million years ago. By this time great mountain chains had formed in the Alps. Himalayas, and elsewhere. Land masses had been uplifted; connection between these latitudes and southern areas was reduced, lessening their heat exchanged and causing greater temperature differences between them. Northern latitudes became progressively cooler after 3 million years, but climate fluctuations between warmer and colder climate regimens were still relatively minor during the first million years of the Ice Age. This was a critically important time, when a more advanced human form evolved in Africa and moved out the tropics into Asia and Europe.
About 730¸000 years ago the earth;s magnetic filed changed abruptly from a reversed state it had adopted about 2.5 million years ago to a normal one. This Matuyama/Brunhes boundary¸ named after the geologist who first discovered it¸ marks the beginning of constant climatic change for the remainder of the Ice Age. Deep sea cores give us a record of changing sea temperatures. They tell us that ice sheets formed gradually¸ but delectation and global warming trends took place with great rapidity. These corresponded with major sea levels rises that flooded low lying coastal areas. During glacial maxima¸ ice sheets covered a full third of the earth's surface¸ mantling Scandinavia and Alps in Europe as well as much of northern North America. Sea levels fell dramatically as a result¸ hundreds of feet below modern levels. The glaciers were about as extensive as they are today during warmer periods¸ the so called interglacials when sea levels were close to present shorelines. Much less is known about changes in tropical regions¸ although it is thought that the southern fringes of Africa's Shara Desert expanded dramatically during cold periods.
Both Homo erectus and its sucessor¸ Homo sapiens¸ evolved during a long period of constant climate transition between warmer and colder regimens in northern latitude. Experts believe that the world's climate has been in transition from one extreme to the other for over 75 percent of the past 730¸000 years¸ with a predominance of cloder climate over the period. There were at least nine glacial episodes, a major one about 525,000 years ago, when there was ice as far south as Seattle, St. Louis, and New York in North America, and sea levels were as much as 650 feet (197 meters) below modern levels. In contrast, there were periods when human settlement outside Africa expanded, as small bands of
foragers exploited the rich animal and plant resources of European and Asian river valleys and forests.
Another intensely cold cycle lasted from about 180,000 to 128,000 years ago, a cycle that coincided in general terms with the period when Homo sapiens sapiens, modern humans, were evolving in Africa. Between 100,000 and 15,000 years ago, the last Ice Age glaciation saw the spread of Homo sapiens sapiens, throughout the Old World and into the Americans. These constant climate changes played an important role in the spread of early human beings throughout temperate and tropical latitudes.
