POINTS & RISK

This chapter will examine the implications of the results that have been presented in the previous chapter.

Throughout the region during the mid-Holocene Period, there was the appearance of what has been previously described as a new implement type, this was the bifacial point. Also shown previously, was that this "new type" can be considered the result of change in stone resource exploitation.

However, bifacial points did impart several benefits and advantages to the prehistoric groups of the region. These benefits and efficiencies used within the subsistence strategies of the group, aided in the exploitation of other resources of the region.

A New Technology

As demonstrated earlier, the variability of stone points in the region includes the entire continuum of form from unifacial points to bifacial points. Bifacial points are not a specific technology per se, they are the result of a maintenance and rejuvenation strategy.

This maintenance and rejuvenation strategy results in an implement, namely a bifacial point, that does display certain advantageous features that would benefit a risk minimisation strategy of resource exploitation. Because stone implements are an integral part of many subsistence strategies for mobile hunter-gatherer groups, anything that has a perceived advantage is desirable (Goodyear 1979). In a multi-purpose toolkit, not all the features of an implement can be interpreted as beneficial for all the functions of the implement. A risk minimisation strategy would require a toolkit containing multi-purpose implements (Beck and Jones 1990).

Length of Cutting Edge

One advantageous feature of a multi-purpose implement is one that maximises the length of the cutting edge. Technologies that can obtain a greater length of cutting edge from the same quantity of raw material demonstrate a valuable use of available resources.

Prehistoric populations faced with a changing environment, and possibly little knowledge of the changing availability of resources, benefited from adopting long lasting multi-purpose implements. Bifacial implements have the potential of providing just such a long lasting, highly efficient and flexible tool. They are well suited to a mobile settlement strategy because bifaces are said to produce the greatest length of cutting edge for unit weight (Goodyear 1979; Andrefsky 1994).

To determine if Goodyear (1979) and Andrefsky’s (1994) proposition held true for the study region, the recorded attributes of weight and perimeter (cutting edge) were used to calculate the length of cutting edge per unit weight value (Table 14).

An examination of the perimeter per weight ratio in Table 14 shows a significant mean difference of the length of cutting edge per unit weight value between Gerowie Tuff unifacial and bifacial points, 3.4 mm/gm (t=4.439,0.001>p>.005). A similar situation exists with quartzite unifacial and bifacial points, with a mean difference of 3.1 mm/gm (t=4.654,0.001>p>0.005). In both of the instances, the bifacial point is providing a considerably longer cutting edge per gram of weight than the unifacial point of the same raw material type (Figure 18).

Figure 18 demonstrates that the length of cutting edge per unit weight varies with different raw materials. As different rock types have differing specific gravities, quartz = 2.4, Gerowie Tuff = 2.8 and Quartzite = 2.9-3.0, the weight of identical sized implements will vary. The difference for different raw materials is more the product of differing specific gravities of each raw material, rather than any inherent property of the particular raw material. From this it is evident that quartzite bifacial points produce the greatest length of cutting edge per unit weight.

Figure 19 demonstrates that the increased cutting edge (perimeter) per unit weight of bifacial points over unifacial points is maintained for all the sites in the study. At both Jimede and Yarar, the increase in edge length, per unit weight for bifacial points, over unifacial points is greater than at the other sites in the study area. The reasons for this are unclear, but may relate to the smaller implement size at Jimede and Yarar.

The perimeter per area value demonstrates that bifacial points have a longer cutting edge per area unit than unifacial points (Goodyear 1979; Andrefsky 1994; Hiscock 1994a). This feature provides little or no benefit when the implement is used as a projectile point. Nevertheless, it is of value when the implement is used as a multi-purpose implement for cutting.

A bifacial point also demonstrates at least two mechanical advantages when they are used as projectile points. These are a more acute tip angle that aids the penetration of game and an increased efficiency index.

Tip Angle & Efficiency Index

The change in stone resource exploitation can now be seen as a technological solution to general changes in the resource base of population groups. When hunter-gatherers move into new environments, they not only are unfamiliar with the food resources, but are also unfamiliar with the location and availability of stone resources. Therefore, they are likely to utilise technologies that are reliable and resource conservative.

Bifacial points have often been seen as purely symbolic because it appears that they conferred no clear advantage over unifacial point or sharpened wooden spears (Akerman 1978; Jones & Johnson 1985). Fris-Hansen (1990) identified a tip angle of less than 50⁰ as the most efficient in Mesolithic, projectile points and the optimum tip angle were found to lie between 30⁰ and 40⁰. To test the hypothesis that bifacial points, do not impart any mechanical advantage beyond an increased length of cutting edge, the tip angle and efficiency of the bifacial points was compared with the unifacial points (Table15).

Table15 shows that within the study area, bifacial points consistently produced a smaller tip angle (41.5⁰) than unifacial points (44.4⁰). The difference in the mean value of the tip angle between unifacial and bifacial points is significant (t = -2.93,0.01 > p >0.005).

The smaller tip angle aids in the projectile point penetrating the hide of the prey. An acute tip angle allows a higher penetration rate when the point strikes the prey at an angle or lower velocity. The acute tip angle can be seen as a beneficial feature in a risk minimisation strategy, by increasing the success rate of the hunter (Fris-Hansen 1990).

A measure of the efficiency of a projectile point can be established by the ratio of the point head perimeter, to the area of the point head. The higher the ratio, the greater predicted injury is inflicted by the point on entering the prey (Fris-Hansen 1990). In Table15 the ratio has been converted to a decimal index and is interpreted as the lower value is a higher level of efficiency. From Table15, it can be seen that on average bifacial points has a higher efficiency than the unifacial points. The mean difference in the efficiency index of unifacial and bifacial points was found to be significant (t = -3.25,0.01 > p >0.005).

A stone point with a higher efficiency is more likely to cause the death of the prey quickly than a less efficient point. If the spear falls out of the prey the high level of internal damage done by the efficient point will result in a higher probability of the prey dying and the hunter being successful. A quick kill is also energy efficient as the hunter is not required to cover large distances to recover the prey. This is important in a risk minimisation strategy for the more efficient gathering of food resources.

While chert produced a smaller tip angle than the other materials, chert bifacial and unifacial points had the lowest efficiency index of the sample. From this it can be assumed that not only were bifacial points potentially more efficient than unifacial points, but that points manufactured from chert were the most efficient of all implements.

In a risk minimisation strategy then, the adoption of a new technology need not impart an increased mechanical advantage over existing technologies. It may however impart an organisational advantage within the overall subsistence strategy (Hiscock 1994a).

Risk Minimisation

The Holocene period marked the end of the last major ice age and the start of extensive environmental changes in the region. While extensive areas of the Sahul shelf were inundated by rising sea levels, thus reducing the available habitable land area and resource base, significant changes where occurring climatically as well. Extensive changes occurred in the climate, environment and resources throughout much of this period. Periods of high resource supply alternated with periods of low resource supply. This has been explored in detail in Chapter 2 of this thesis. It is sufficient here to note, that the supply of both food and stone resources fluctuated during the period.

Bifacial flaked stone points occur approximately midway through the period of most rapid change. Of the sites included in this study, the earliest occurrence is at Jimede II 4770 ± 150 B.P. (Schrire1982). The oldest recorded occurrence in the region is at Nauwalabila 1, which is not included in the study, with a radiocarbon date of 5860 ± 90 B.P (Jones & Johnson 1985:206), doubts have been expressed regarding this date by Allen & Barton (1989). They do agree, however, that points were in widespread use by 5,000 BP and may have ceased by 1,500 BP (Allen & Barton 1989; Hiscock 1994a). Table 16 presents the major environmental episodes and the appearance of points.

Bifacial points appear in the archaeological record during the transitional phase (5-300 – 4,000 B.P.) when the resource abundant mangrove forests of the big swamp phase was in decline. In times of radically changing environments, such as those in Table 16, specialised subsistence strategies are likely to be used (Kelly & Todd 1988; Hiscock 1994a). These strategies will affect the approaches made to solve the technological problems required for the strategy’s success. Several authors have identified a particular subsistence strategy termed a risk minimisation strategy (Hiscock 1994a; Kelly & Todd 1988).

In this strategy, it is argued that population groups moving into unknown and new areas are unfamiliar with the location and availability of both stone and food resources. In these circumstances, there is often a primary reliance on fauna rather than flora food resources. This results from fauna being generally more readily available throughout the year and being less affected by the seasons than flora. It, therefore, takes a much shorter time to develop a knowledge base regarding fauna, than it does flora food resources.

The sites used in this study provide a spatial positioning within the landscape for various prehistoric groups. Sites are positioned to enable the utilisation of a variety of resources. The same situation arises when the population may be relatively static but the prehistoric group’s environment is changing. Instead of being faced with a uncertain location of new resources, the group experiences the disappearance of existing resources and a gradual expansion of new resources. These resources include food supplies, shelter and water, collectively referred to as the environment and artefactual raw materials.

The Scotch Creek site is located on the banks of a freshwater billabong on the Adelaide River floodplain. This permanent water supply contains estuarine crocodile (Crocodylus porsus), barramundi (Lates calconifer), freshwater tortoise (Chalodina longicollis) and watefowl. The open Eucalypt woodland near the site, supports mammals such as the agile wallaby (Macropos agilis) and raw materials for stone knapping are located within 5km of the site (Smith & Brockwell 1994).

Scotch Creek then is positioned closer to the food and water resources rather than at the raw material resources. This indicates that food and water resources were considered to be a higher economic cost than stone resources. Flood (1969) identified a similar consideration at Yarar, as it is only occupied during the wet season when there was abundant freshwater. Prehistoric occupants at Yarar were forced to adopt a seasonal occupation regime due to the lack (high cost) of water at the site during the dry season.

A site will have a particular importance and positioning relative to a raw material source. If the site is in close proximity to a suitable raw material source, the economic cost of creating new implements is relatively low. A site that is located more remotely from the preferred raw material, means that new implements have a higher economic cost. Knappers at these sites will adopt technological strategies that minimise these costs and prolong the implement life (Goodyear 1979; Kelly & Todd 1988).

When the supply of an important resource is lost, the site may be abandoned. At Ngarradj Warde Djobkeng and Malakunanja II, Allen & Barton (1989) have argued for a termination of the site occupation that corresponds with the end of the mollusc resources of the Big Swamp Phase.

The spatial positioning of a site will also influence the food gathering strategies adopted, and hence the implements required, for satisfying these strategies. In sites such as Malangangerr 1, not included in this study, there is evidence of a diverse food collection strategy. Unlike Ngarradj Warde Djobkeng the faunal successions at Malangangerr 1 is not limited to mangrove shellfish. There is wallaby (Petrogale bradyotis), possums (Trichosurus arnhemesis), freshwater turtle and shellfish as well as catfish (Neosilurus sp.) (Schrire 1982).

A more diverse faunal succession may also indicate a period of resource diversification. After a period of decline in the molluscs of the Big Swamp Phase mangroves, sites such as Ngarradj Warde Djobkeng, which relied on the mollusc as a primary resource, were abandoned. The decline in resource forced a movement away from the sites at about 3,000 B.P. (Allen & Barton 1989). As the environment continued to change, new flora and fauna species began to be established. This produced a highly resources variable environment for the next 1,500 years. The diverse nature of the Malangangerr 1 faunal succession is indicative of such a change.

To deal with an environment, when resources are fluctuating and there is a changing diversity, such as demonstrated by Malangangerr 1, a risk minimisation strategy is beneficial. The variability of stone points demonstrate an application of a technology well suited to use in a risk minimisation strategy (Goodyear 1979; Kelly & Todd 1988; Hiscock 1994a).

Conclusion

Implement variability and changes in resource utilisation should not be restricted to single isolated factors. The combined influence of the system as a whole, that includes the environment, stone resources, food resources, function and social structure all interact together (O’Connell & Allen 1995; Frankel 1995; Kelly & Todd 1988; Hiscock 1994a). Grace (1994) has described this interplay of multiple forces as chaos complexity.

The study clearly demonstrated that the scale of resolution, to which the sample is analysed, strongly influences the appearance of homogeneity within the sample. Observe the sample as a single entity, is to overlook individual dissimilarity that is no longer observable. When implement variability is examined at higher resolutions, and biases such as those produced by raw materials and spatial positioning are considered, the technological strategies adopted by prehistoric populations become visible.

Changes in resource exploitation cannot be considered in isolation. It must be interpreted in conjunction with other factors across a number of sites. These factors include environmental change, raw material properties and the spatial position of a site relative to the available resources.

Stone Point Variability

Future Research

Author: Wayne Roddom, Dept. Archaeology and Anthropology
Feedback: peter.hiscock@anu.edu.au .
Date Last Modified: 5-June 1998
URL: http://artalpha.anu.edu.au/web/arc/aboutus/studs/points.htm