Chapter 15
THE SUNDA SHELF
During the Pleistocene ice age, water froze and covered a large part of the northern hemisphere landmass with ice and glaciers on a gigantic scale, which resulted in the level of the seas and oceans falling. At one hundred and twenty metres below today’s sea level, the Sunda Shelf emerged to form a continuous land mass with what is now South East Asia, called Sundaland by geologists.
During this same period Homo erectus left Africa, advancing slowly, kilometre by kilometre with each generation, until he finally crossed into Sundaland and spread across the region into what is now Java by about 1.9 million years ago. Who was Homo erectus? Paleoanthropologists seem agree that he had evolved from Homo habilis according to the evidence of the fossils found at Lake Turkana in Kenya, which dated back two million years, and showed transitional characteristics between the two species.
Homo erectus walked in an upright position in much the same manner as modern man. However, the skull bore many primitive features, such as heavy brow ridges and other features. The bipedal gait had in fact been inherited from his ancestor and was in fact not a new characteristic in hominids, which according to fossil evidence found in Kenya, goes back six million years.
When the Dutch military doctor, Eugene Dubois, discovered in the 1890’s a fossil skullcap and the thighbone of a hitherto unknown type of human at the site of Trinil in Java, he called it Pithecanthropus erectus, which means upright ape-man. Today these fossils are considered by paleoanthropologists to belong a species baptised erectus and part of the genus Homo. The age of the fossils were then estimated to be around 750,000 years old.
However, many years later a new dating technique, called potassium argon, was used to carry out tests on rock samples from the strata in which the erectus fossils had been found, to the surprise of the scientific world the new method indicated a date of around 1,9 million years old. This clearly showed that Homo erectus had migrated out of Africa much earlier then thought, crossing Asia and arriving by foot to Sundaland more than 10,000 kilometres from the point of his origin in Africa.
What had astonished scientists was that Homo erectus had appeared in Asia so early, as prior to this new dating he was not thought to have migrated from Africa until about one million years ago, in fact when erectus appeared in the fossil record in Africa evidence of his presence in Asia at that time alredy existed.
As the climate changed once more and as the sea levels rose Homo erectus was left isolated on what was to become the Island of Java, until the late Pleistocene, when the sea level dropped once again during the last glaciation, re-establishing the land links with the Asian mainland.
Erectus lived in the rain forest as a hunter gatherer using caves as shelters. Such caves only formed in a certain types of rock, usually limestone, marble, or gypsum. These hominids had little more effect on the ecosystems than any other forest animals such as the orang-utans with whom they certainly competed and perhaps drove them from the forest floor into the trees. Fossils evidence shows that the orang-utan, a member of the family of great apes, was larger in the Pleistocene period and had characteristics that are evidence of a terrestrial past.
When Homo sapiens arrived across the newly established land bridge 60,000 years ago, he certainly competed with Homo erectus for food and shared the same territory. As a consequence the small Homo erectus population suffered the same fate as did the Neanderthals in Europe with their extinction when a competitor arrived equipped with a more evolved technology and culture.
Culture is the knowledge each generation passes on to the next, knowledge that had been acquired by learning that is to say all aspects of human adaptation, including technology, traditions, language and social roles. Culture is learned and transmitted from one generation to the next by non-biological means. Paleoanthropologists believed that Homo erectus had not possessed an advanced language capacity and his capacity for symbolic thought and thus his tool making ability was less than that of early Homo sapiens.
Language and tool making are cultural characteristics that are not instinctive, they are learned and transmitted from generation to generation, these characteristics are not fixed as are genes and culture, which is easily be lost or modified by outside factors. Culture can also change very rapidly as it is independent of biological change and genetic inheritance.
Whilst cultural factors can provide a short term solution to outside change, genetic adaptation ensures long term survival. Though the ecological changes due to volcanic activity, such as the gigantic explosion that created Lake Toba in Sumatra, may have had catastrophic, though short term effects on local climate and food resources, the climatic conditions in the forests of Borneo were extraordinarily stable, and as a consequence the survival of random genetic changes in the small population would have borne no specific advantage.
Climatic changes, in general, resulted in a combination of cultural and biological changes in hominid populations. Culture teaches a population that certain types of food are edible, enabling them to survive when other kinds of food becomes unavailable as a result of climatic change, such as extreme cold or drought. Thus mutations that occur in a group would be tested over a number of generations and their eventual assimilation into a population could effect the survival of the group.
Such climatic changes occurred in different regions of the world but most notably in Africa, where new forms of man emerged, obeying the harsh natural law of the survival of the fittest. Climatic conditions forced groups to seek new territories bringing about competition between existing populations and newly arrived and more advanced species, which resulted in the extinction of the less adaptable populations. It was the case of Homo sapiens, who had a competitive advantage over the existing populations they met as they migrated out of Africa. The founder population of Homo sapiens was very small, perhaps no more than a few hundred individuals or even less, but their competitive advantage was great and within 60,000 years or so, this new species of man had spread out reaching Australia, conquering the world, then finally replacing all other species of man who gradually became extinct.
What was extraordinary was that the existing populations of Homo erectus, more than a million men, women and children, completely disappeared from every corner of the earth as Homo sapiens took hold of their newly conquered territories. Homo erectus, who had discovered fire, manufactured tools, and who had survived for two million years of climatic change and without doubt epidemics of disease and unknown catastrophic natural events, simply disappeared off the face of the planet.
Whatever the reason the newcomers from Africa replaced the not only Homo erectus, but also Neanderthals and archaic Homo sapiens. The only question that remains and that troubles many scientists is whether interbreeding had occurred between the different populations.
In such conditions could relic populations of Homo erectus have survived until recent times in very remote and isolated regions? It is only normal and natural that they did. Looking around the world today there are many examples of such relic populations in other animal species, there are the Komodo Dragons of Indonesia and on a larger scale are the marsupials of Australia, unknown until Cook reached that continent. At the end of the twentieth century relic populations still exist, as man continues to impose his devastating conquest into the very last distant corners of the planet, exterminating the last remaining populations of non-human primates: lemurs, orang-utans, bonobos, mountain gorillas…and so many other species.
The Lost Forest Page 15