Dispersion and growth of regionality: 50,000-35,000 years ago
Our record of the physical form of people who dispersed across Sahul comes principally from the skeletons that have been recovered from the southeast. Human skeletons dating back about 43,000 years have been preserved at Lake Mungo.
These remains are the visible indication of the early and widespread settlement of the continent soon after colonization. They also provide a remarkable insight into physical characteristics of the people dispersing into the new environments. A key example is the body of the individual labelled WLH3. We cannot tell if this was a male or female, but they were an older adult with osteoarthritis in the vertebrae and right arm, and teeth worn down so much that the pulp cavities were exposed. The head of WLH3 was spherically shaped, with a high forehead and moderately thin cranial bones; the face was relatively flat and above the eye sockets there was only a slight thickening of bone along the supraorbital ridge, giving it a modern appearance.[568] Ancient mtDNA has been extracted from this skeleton, and although there have been some concerns about the extent of postmortem destruction of the DNA and the chance of contamination, the results offer clear evidence that WLH3 was from a distinctive ancient Aboriginal lineage.1[569] This individual was an ancestor of modern Australian Aboriginals. The mtDNA sequences of WLH3 are still known in living people, showing that those ancient lineages still exist. This demonstrates that after the colonization there were no substantial later migrations into Australia during prehistory, and certainly the founding populations were never replaced by later incoming populations.[570] This outcome reflects the extent to which the colonizing population grew in size as it progressively occupied each part of the continent, until the overall population was very large; small groups who subsequently arrived would not have had much impact on the gene pool across the continent.[571] The Sahul mtDNA evidence is consistent with a single colonization event followed by a long period of genetic isolation. Physical and cultural variation evident in the Australian archaeological, historical and biological records emerged largely from adaptations to social and physical environments within the continent.WLH3 was buried at Lake Mungo in southern Australia after his/her ancestors had gradually spread from landing points along the northern coast. The dispersion of humans across Australia probably began shortly after humans arrived on the shores of the continent. Even acknowledging the ambiguity created by uncertainties in radiometric dating techniques the minimum antiquity for sites in many portions of Australia is little different. As described above, the earliest sites in Arnhem Land show evidence for occupation about 50,000-60,000 years ago and archaeological sites further south across mainland Australia and to the northeast in New Guinea have evidence of initial occupation dating to more than 45,000 years ago. This evidence documents human settlement of many ecosystems: in sandy deserts (Puritjarra), rocky deserts (Allen's Cave), semi-arid grasslands (Cuddie Springs), tropical savannah (Malakunanja), tropical woodland (Ngarrabull- gan), tropical coasts (Mandu Mandu Creek), and southern alpine uplands (Parmerpar Meethaner).[572] Homo sapiens dispersed across the accessible portions of the continent, settling multiple different environments, but did not penetrate locations surrounded by substantial geographical barriers such as Bass Strait. From before 50,000 years ago the colonizing population was not restricted to any specific environment, or to the coastal margins. Settlers entering each environment had flexible and adjustable economic systems and this, combined with expanding populations, created the capacity to occupy the diversity of environments within the Sahul landmass. Economic strategies may have been transformed early in the colonizing process following humanly induced changes to the environment of Sahul.
The expansion of people across all of these different environments is likely to have been facilitated by population increase.
While genetic studies suggest early population growth this has been difficult to see in the archaeological record. The abundance of radiocarbon age-estimates has been used as a measure of demographic trends, on the presumption that dated charcoal comes from hearths and that there is some fixed relationship between hearths and number of people. The demographic curve proposed implied minimal growth until recent millennia, a pattern that is not congruent with genetic evidence.[573] It is likely, however, that few early hearths were preserved, so the carbon record has decayed, and is therefore insensitive to the demographic processes that may have underpinned the dispersion and settlement of people across Australia.A much debated, but largely unresolved, question about this initial period of settlement is whether the appearance of human hunters had a significant impact on Australasian environments. One focus of research into this question is whether the humans dispersing across Australia were an agent causing the extinction of animal species. Fossil bones show that a suite of very large animals had lived in Australia at some time prior to the arrival of humans: giant kangaroos (such as Macropus rufus and Macropus giganteus titan) and giant wombat (Phascolonus gigas), tall flightless birds (Genyornis sp.), fourlegged marsupial browsers and grazers the same size as some species of hippopotamus and rhinoceros (such as Diprotodon optatum, Zygomaturus sp., Palorchestes sp.). In island landscapes such as New Zealand there is a repeated pattern of human hunters entering the environment for the first time, targeting and over-exploiting large animals to such an extent that human predation was a significant contributor to the extinction of species. Since in Australia some studies found a broad coincidence between the time at which species of large marsupials disappeared and the time that humans arrived, it seems likely that the human colonization of Australia might have triggered a trophic collapse in which particular kinds of animals were driven to extinc- tion.20 If the early dispersal model is correct, as is likely, and Homo sapiens has spread from Africa across Eurasia exploiting a great diversity of animal resources in varied niches, then the humans who arrived in Sahul were the descendants of many generations of accomplished and adaptable hunters.
As skilful predators whose hunting behaviours were unfamiliar to marsupial prey the dispersing humans no doubt had the capacity to reduce the viability of vulnerable species, especially if hunters targeted the young of animals that reproduced slowly and/or if the prey species were limited in distribution and predictable in movement such as being tethered to rare resources.[574] [575]However, archaeologists in Australia have never found killing sites where large extinct animals were killed and their bodies butchered in preparation for transport of the meat back to campsites. This is curious because in other lands, most notably the Americas and New Zealand, kill sites have been found in abundance during periods in which hunters targeted large game. Perhaps there is a minimal archaeological signature of early hunting because the extinction process occurred very quickly and because it was long ago, diminishing the chance of bones being preserved, and yet it seems unlikely that if hunting of now extinct animals was intensive no butchered animal bones would have been identified even in the few archaeological sites with favourable preservation.[576] There are few archaeological sites older than 35,000-40,000 years bp with bones well-preserved, but those that have been found show a hunting focus on small rather than large game.
One site that might have evidence for butchery of naturally trapped animals, though not for hunting, is Cuddie Springs, which has stone artefacts and bones of extinct animals together in levels 33,000-40,000 years old.[577] Evidence of humans still butchering the extinct species as late as 33,000 years ago, perhaps 15,000 years after people occupied the region, is not consistent with the notion that early hunting targeted species with large body mass to such an extent that those species were rapidly exterminated.[578] For this reason the reality of the apparent association between artefacts and fossil bones at this site is critical, and has been persistently challenged, with indications that dating and stratigraphic associations are complex and that extinctions might have occurred earlier, near the initiation of human occupation.[579] If Cuddie Springs is eliminated from consideration on that basis there is little or no archaeological evidence that bears upon the question of large mammal extinctions.
A variety of environmental signatures consistently point to the reduction in range and density of large animals, if not their final extinction, between 40,000 and 50,000 years ago, and so the correspondence between the spread of humans and the stress on faunal populations suggests that the appearance of human hunters in the landscape is implicated in the extinction process.[580] The timing of population reductions in these animals coincides with
Colonization and occupation of Australasia intensification of long-term continental drying, reductions in resource levels and restructuring of the environment, and so even low levels of predation by the new human hunters may have tipped some species into terminal declines, or accelerated declines already underway.[581] Most likely it was not intensive or exclusive hunting of these large animals that reduced their populations perilously but merely the addition of a new social carnivore to stressful ecological circumstances.
While the extinctions themselves have captured the imagination of researchers it is the removal of those animals from the Australian landscape that shaped subsequent human occupation, as Flannery observed.[582]The consequences of a reduction in the number of large marsupials, and subsequently their extinction, would have been dramatic. Removing large browsers and grazers from the ecosystem means they are not actively consuming vegetation, potentially resulting in reduced openness within forests, reduced ecosystem patchiness and increased fuel load, which might facilitate altered fire regimes and subsequently nutrient cycles. Evidence of this chain of ecological transformation is recorded from several places, but most notably from Lynch's Crater, a swamp in northeast Australia. Cores drilled into the deep sediments of this swamp provided a record of pollen, charcoal and spores of the fungus Sporormiella, which is passed through the bowel of large herbivores and can be used as a proxy for their presence in a landscape.[583] Counts of Sporormiella spores, and by implication the abundance of large herbivores, declined markedly about 41,000 years ago. Immediately afterwards, charcoal fragments in the sediments, and by implication fire frequency/intensity, increased in response to increased fuel. The sequence from Lynch's Crater is consistent with charcoal pulses in many sedimentary sequences across Australia dating to between approximately 40,000 and 50,000 years ago.[584] Although these charcoal signals have often been discussed as possible signals of the arrival of humans it is more likely, given the earlier dates now available for occupation, that altered burning regimes mark the
point at which new ecological relationships emerge in a land now largely devoid of very large herbivores.
Settlement of new territories across the continent may have been assisted by the exploitation of substantial meat packages represented by the large herbivores, but that prey would have been found in small numbers, geographically variable in abundance and for only a limited period, and consequently early foraging practices would have been reasonably diverse.
Certainly the early archaeological assemblages of animal bones are a consequence of flexible foraging strategies focused on hunting a wide range of small- to medium-sized game. The prey composition in each locality reflected a selection of animals from the suite of game locally available. For example, early desert economies, at least in the period 35,000-45,000 years ago were often based on the exploitation of large, permanent desert lakes as reliable resource-rich zones. Sites of this kind, such as Lake Mungo, contain the remains of marsupial species, reptiles, as well as fish and mussels. Fishing was accomplished with a range of technologies, including spears, nets and hook and line; while terrestrial hunting used spears and perhaps traps and thrown artefacts such as sticks or perhaps even boomerangs (though these are not reliably dated before 10,000-15,000 years ago). It is likely that plant foods such as yams and seeds would have supplemented meat in the deserts, and that these would have varied between environments, though the archaeological evidence for this foraging is rare. Regional differences in economic strategies, probably combined with disparate demographic histories, most likely underpinned regional differences in cultural practices that emerged as each landscape was settled and groups adapted their social life to the specific circumstance they encountered.Regional traditions of behaviour are clear in this period, and especially visible in technology and symbols. Geographical difference in technology is revealed in the stone artefact assemblages, which have preserved extremely well.[585] Most obvious is the manufacture and use of hafted edge-ground axes in northern Australia but not in southern Australia.[586] Additionally the technology for making tools through flaking differed across the continent in response to raw material characteristics and the economic incentives to produce expedient or maintained, and large or small tools. Such technological variations are not simply adaptations to local stone materials; they also indicate the transmission of local conventions of tool manufacture and tool use. This is substantiated by the regional-scale difference in public signalling through symbols 40,000-50,000 years ago. In this period jewellery, probably in the form of necklaces or bracelets, made of perforated shells or bones with mastic and ochre, was made only in the northwestern portion of the continent. Its absence in the east and south is not a consequence of poor preservation since in some localities, especially the Tasmanian uplands, there are well-preserved faunal assemblages but no beads. At the very least this indicates regional traditions in the way ornamentation was produced, with only perishable plant materials being used for jewellery in the southeast, and it may well indicate the absence of ornamentation across a substantial portion of the continent in the millennia following settlement. A similar pattern of regional difference exists in the residues of painted art production. Small ochre fragments have often been recovered from the sediments of occupied caves, often the only visible evidence of art on the walls that disappeared long ago, and the changing abundance of ochre in different levels of the deposit may indicate changing intensities of rock painting. This phenomenon is most pronounced in the northern and western portions of the continent and has rarely been reported in the southeast. Furthermore, ochre pallets with ground facets are typical of northern Australia and it may be that paint was prepared in a different way in the south. Ochre was used in the southeast, such as in the burial of WLH3, where it was scattered around the interred body before the grave was closed, so we know these regional differences were not the pres- ence/absence of symbol use or ritual, but different expressions of those activities. Hence a range of archaeological indicators reveal different symbolic expressions between north/northwestern regions and south/southeastern ones, and perhaps more local traditions that have not yet been defined.
These cultural differences emerged as human groups settled different environments, most likely in part through a process of drift and also as they adjusted their social and cultural systems to historically contingent situations confronting them. Even during the early millennia of settlement it was geographical diversity and cultural adaptation rather than pan-continental uniformity and cultural stability that were the features of human occupation of Sahul.