Monday, June 14, 2010

Ancient Prehistory: 60,000–22,000 BP

Since the arrival of the first Aboriginal people about 60,000 years ago, the Australian continent has undergone tremendous change. When they arrived, present-day Australia, Tasmania, the Torres Strait Islands, and the island of New Guinea were all connected. These lands formed the continent of Sahul, a landmass approximately the size of contemporary Europe west of the Ural Mountains. The continent contained a large number of unique plant and animal species due to its long period of isolation (about 38 million years) from other landmasses, including an estimated 13 species of so-called megafauna. These were very large versions of contemporary kangaroos, wombats, and other marsupials; many other species of megafauna had died out prior to the continent’s inhabitation by humans. The climate was generally cooler and drier than the region is today, with periglacial and even glacial regions in the Highlands of New Guinea and the Dividing Ranges of southeastern Australia. Nonetheless, Sahul 60,000 years ago encompassed the same wide variety of ecological niches as today’s separate landmasses. Tropical forests covered the northern lowlands, while temperate forests existed in the south and highlands of the north. The center of the continent contained both deserts and savannahs, as it does today. Some pollen studies appear to show that even the continent’s dry center contained some forest land, but this hypothesis has not been accepted by all archaeologists or other scientists working in this area.

Even though there is no absolute certainty about the direction from which the ancient migrating population arrived on Sahul, the most viable hypothesis is that after spending thousands of years leaving Africa, passing through the Middle East and India, and heading south through mainland Southeast Asia, which was then much larger than today, a small group of migrants sailed across about 35 miles of open sea to land somewhere in Sahul’s far north, or contemporary New Guinea. Other hypotheses, such as migration direct from India or even the in situ evolution of humanity in Sahul, have been disproven in recent decades with the development of mitochondrial deoxyribonucleic acid (mtDNA) analysis.

Like the migration route, the period of initial migration is also a highly contested feature of Aboriginal Australian history that involves archaeologists, physical anthropologists, geneticists, linguists, botanists, and a host of other scientists. Most Aboriginal people themselves find this debate irrelevant or even insulting, for it discounts their own origin myths, which are timeless. Nonetheless, until the 1960s, most scientists believed the original period of migration was as recent as about 10,000–12,000 years ago, or about the same time as the colonization of the Americas from northern Asia. With the development of advanced carbon 14 dating techniques, this date was pushed out toward 40,000 years before the present (BP) by the middle of the 1980s. And with the development of thermoluminescence dating in the 1990s, 60,000 years BP has become a common estimate. Genetic testing of mitochondrial DNA, which looks at female lineages of certain genes and determines age through the evaluation of gene mutations, has also provided dates of around 60,000 years BP for the initial peopling of the continent.

Nonetheless, contradictory evidence from other disciplines has compelled scientists to continue exploring this intriguing subject. For example, pollen studies that show an increase in the existence of fire on the continent, which may indicate human use of fire to clear territory and make hunting easier, have indicated that it is remotely possible that humans were using fire in Australia as far back as 185,000 years ago. The use of TL on materials found in Jinmium, Western Australia, has likewise produced a date as far back as 176,000 years, though this has since been forcefully rebutted by others. On the other side of the debate, archaeologists have found very few sites in Sahul that can be verified as having existed more than 40,000 years ago. In their review of all the evidence that had been retested using thermoluminescence and other techniques, O’Connell and Allen (2004) conclude that even with these new technologies, 45,000 BP is the earliest date for which we can be certain of human inhabitation of Sahul. Nevertheless, because their conclusions do not take genetic evidence into account, many consider this a conservative date.

Another problem with our understanding of the initial peopling of Sahul is whether one migrant population settled and spread slowly to all corners of the continent, from the Highlands of New Guinea to the southern tip of Tasmania, or whether there was a continual flow of migrants over many thousands of years. Discrepancies in the archaeological record, such as the fact that the oldest archaeological sites have been found in Australia’s southeastern states of New South Wales and Tasmania rather than northern regions, and the odd division of Australian languages into two groupings, Pama-Nyungan and non-Pama-Nyungan, have convinced many scholars over the years that Australia was populated by several waves of people from India as well as Southeast Asia. In addition, simulation studies, which use computer modeling in the creation of hypotheses, have posited that there have to have been multiple migratory groups to Sahul to prevent incest and sex imbalances.

What these simulation studies do not tell us, however, is whether or not these multiple migrations took place over several years, decades, centuries, or even millennia. As a result of recent studies, physical anthropologists and geneticists working in the area of mtDNA believe they have answered this long-standing question in favor of the shortest possible time lag between migrations. Their data show with relative certainty that Australia, New Guinea, and all of Melanesia were populated by a single group of migrants who left Africa 70,000 years ago at the earliest and populated their current home about 58,000 years ago, plus or minus 8,000 years (Hudjashova et al. 2007). This same evidence also points to a long period of relative isolation after this initial migration, whereby even prior to the submergence of the land bridge linking Australia and New Guinea, the populations of these two regions remained largely separate. The only exception to this trend evidenced by the genetic material tested so far is an influx of New Guineans into northern Australia about 30,000 years ago.

The history of this population remains fairly vague after they began settling Sahul. We do not know whether communities fought wars against each other or were so spread out on the vast continent as to be able to live peaceably. We do not know how soon their proto-Australian language or languages began dividing into the vast number of Australian and Papuan languages evident by the time of European contact in the 17th century. We do not know whether the Dreaming stories and their accompanying rituals, which make up the backbone of Aboriginal religion even today, were imported with them, were developed during the period of migration, or were begun after settlement on the continent. The list of unanswered and probably unanswerable questions about this most ancient of populations is very long.

Nevertheless, on the basis of the somewhat sparse archaeological record of about 100 sites identified to be older than 22,000 years, the period of the last glacial maximal (LGM) and a period of dramatic change on the continent, we do have a very good idea about a few aspects of life on prehistoric Sahul. Archaeologists working at sites as far removed as Lake Mungo’s Willandra area in western New South Wales, Parmepar Meethaner in Tasmania, and Yombon on New Britain, New Guinea, have found remains dating from before 22,000 BP. While some aspects of these ancient populations’ tool kits and subsistence regimes were similar, others differed. For example, people in all three regions lived on a food collectors’ diet consisting largely of fish, shellfish, and small mammals. Of course local fruits, roots, greens, mushrooms, and other gathered foods would also have made up a substantial portion of their diet, as attested by the evidence provided by contemporary food collectors. But none of these foods left behind remains that could survive in middens, prehistoric garbage dumps the way that shells and bones could, and so their exact importance can only be surmised today. Other material finds include grinding stones for processing seeds and grains; tools made from flaked chert (a sedimentary rock), which often had been carried relatively long distances; and even a few tools prepared from animal bones, mostly those of kangaroos and large wallabies. In the north heavy stone axes have been found in the most ancient middens, while in the south this kind of tool emerged only in the past few thousand years (Hiscock 2008, 110).

Midden of mollusk shells and crustaceans near Weipa, on the northwest coast of the Cape
York Peninsula, Queensland (National Archives of Australia: A1200, L26732)

In addition to information about the content of the earliest Aboriginal people’s diet and tool kits, middens are important sources of information about ancient social structures. The small size of the pre-LGM middens found in Australia, Tasmania, and New Guinea indicates that the people who created them must have migrated often, from daily to seasonally, depending on locale and season. This kind of migration pattern is generally indicative of very low populations and population densities; relative equality between all adults, where the only distinctions are age and sex; no craft specialization or division of labor aside from those based on age and sex; no formal political or leadership roles; no concept of private property; a highly varied diet; and minimal risk of starvation.

Cultural anthropologists refer to societies organized in this manner as bands, social units made up of groups of related people who live together, move together, and, when necessitated by food shortages or conflict, split up and create two new bands or move in with other kinsfolk to expand preexisting bands. This inherent mobility, which facilitates access to foods as they ripen or become available and ability to harvest them in a sustainable manner, also limits people in band societies to minimal portable possessions, usually just carrying bags, weapons, and possibly some light tools or ritual objects. Everything else, from heavy stone tools to clothing, is made from local resources in each new residence. Housing would have been in either caves or leantos made anew in each location.

Some of the features associated with band societies, such as having a highly varied diet and minimal risk of starvation, may seem contradictory to the modern image of premodern life as “solitary, poor, nasty, brutish, and short,” as Thomas Hobbes put it in 1651. And we cannot be certain that life in pre-LGM Sahul was similar to the life of food collectors who lived in bands in the 20th century, where on average only about four hours per day were required to make, gather, and hunt all the necessities of life. Nonetheless, there is no evidence that this ancient Sahul population differed significantly from these more contemporary band societies. The Australian environment probably provided significant protein and vegetable matter in the form of seafoods, fish, mammals, grubs, roots, and fruit. The very low populations and population densities probably allowed each group to move as needed to seek out sources of food and water. Unlike most agricultural societies, which are at great risk of famine because most calories are consumed from just one grain, such as corn, rice, or wheat, or from a single starch such as sago, potatoes, or cassava, food collectors have access to a wide array of foods. There is very little risk inherent in food collecting because when there is a shortage of one food, a variety of others is usually available, and there is always the possibility for migration to new, more resourcerich areas.

In general, then, we can conclude that life in pre-LGM Sahul was of a very small scale. Small groups of related individuals moved with relative frequency to find food, shelter, and water. While all adults likely had a say in a move, the words of elders and men were probably taken more seriously than those of younger people or women. This is merely conjecture, but evidence of other food collecting band societies, including Aboriginal Australians at the time of European contact, suggests that men’s freedom from pregnancy and breast-feeding probably gave them greater mobility, knowledge of further distances, and thus a greater say in a band’s movements. Aside from these differences based on age and gender, these societies would have exhibited no class or caste distinctions and all members of the band would have had access to food and other things as needed.