Brian F. Codding

The “fire stick farming” hypothesis: Australian Aboriginal foraging strategies, biodiversity, and anthropogenic fire mosaics

Aboriginal burning in Australia has long been assumed to be a “resource management” strategy, but no quantitative tests of this hypothesis have ever been conducted. We combine ethnographic observations of contemporary Aboriginal hunting and burning with satellite image analysis of anthropogenic and natural landscape structure to demonstrate the processes through which Aboriginal burning shapes arid-zone vegetational diversity. Anthropogenic landscapes contain a greater diversity of successional stages than landscapes under a lightning fire regime, and differences are of scale, not of kind. Landscape scale is directly linked to foraging for small, burrowed prey (monitor lizards), which is a specialty of Aboriginal women. The maintenance of small-scale habitat mosaics increases small-animal hunting productivity. These results have implications for understanding the unique biodiversity of the Australian continent, through time and space. In particular, anthropogenic influences on the habitat structure of paleolandscapes are likely to be spatially localized and linked to less mobile, “broad-spectrum” foraging economies.

IN PURSUIT OF MOBILE PREY : MARTU HUNTING STRATEGIES AND ARCHAEOFAUNAL INTERPRETATION

By integrating foraging models developed in behavioral ecology with measures of variability in faunal remains, zooarchaeological studies have made important contributions toward understanding prehistoric resource use and the dynamic interactions between humans and their prey. However, where archaeological studies are unable to quantify the costs and benefits associated with prey acquisition, they often rely on proxy measures such as prey body size, assuming it to be positively correlated with return rate. To examine this hypothesis, we analyze the results of 1,347 adult foraging bouts and 649 focal follows of contemporary Martu foragers in Australias Western Desert. The data show that prey mobility is highly correlated with prey body size and is inversely related to pursuit success—meaning that prey body size is often an inappropriate proxy measure of prey rank. This has broad implications for future studies that rely on taxonomic measures of prey abundance to examine prehistoric human ecology, including but not limited to economic intensification, socioeconomic complexity, resource sustainability, and overexploitation.

Aboriginal hunting buffers climate-driven fire-size variability in Australia’s spinifex grasslands

Across diverse ecosystems, greater climatic variability tends to increase wildfire size, particularly in Australia, where alternating wet–dry cycles increase vegetation growth, only to leave a dry overgrown landscape highly susceptible to fire spread. Aboriginal Australian hunting fires have been hypothesized to buffer such variability, mitigating mortality on small-mammal populations, which have suffered declines and extinctions in the arid zone coincident with Aboriginal depopulation. We test the hypothesis that the relationship between climate and fire size is buffered through the maintenance of an anthropogenic, fine-grained fire regime by comparing the effect of climatic variability on landscapes dominated by Martu Aboriginal hunting fires with those dominated by lightning fires. We show that Aboriginal fires are smaller, more tightly clustered, and remain small even when climate variation causes huge fires in the lightning region. As these effects likely benefit threatened small-mammal species, Aboriginal hunters should be considered trophic facilitators, and policies aimed at reducing the risk of large fires should promote land-management strategies consistent with Aboriginal burning regimes.

Provisioning offspring and others: risk–energy trade-offs and gender differences in hunter–gatherer foraging strategies

Offspring provisioning is commonly referenced as the most important influence on mens and womens foraging decisions. However, the provisioning of other adults may be equally important in determining gender differences in resource choice, particularly when the goals of provisioning offspring versus others cannot be met with the acquisition of the same resources. Here, we examine how resources vary in their expected daily energetic returns and in the variance or risk around those returns. We predict that when available resources impose no trade-off between risk and energy, the targets of mens and womens foraging will converge on high-energy, low-risk resources that allow for the simultaneous provisioning of offspring and others. However, when minimizing risk and maximizing energy trade-off with one another, we expect mens foraging to focus on provisioning others through the unreliable acquisition of large harvests, while women focus on reliably acquiring smaller harvests to feed offspring. We test these predictions with foraging data from three populations (Aché, Martu and Meriam). The results uphold the predictions, suggesting that mens and womens foraging interests converge when high-energy resources can be reliably acquired, but diverge when higher-energy resources are associated with higher levels of risk. Social factors, particularly the availability of alloparental support, may also play a major role.

Niche construction and Dreaming logic: aboriginal patch mosaic burning and varanid lizards ( Varanus gouldii ) in Australia

Anthropogenic fire is a form of ecosystem engineering that creates greater landscape patchiness at small spatial scales: such rescaling of patch diversity through mosaic burning has been argued to be a form of niche construction, the loss of which may have precipitated the decline and extinction of many endemic species in the Western Desert of Australia. We find evidence to support this hypothesis relative to one keystone species, the sand monitor lizard (Varanus gouldii). Paradoxically, V. gouldii populations are higher where Aboriginal hunting is most intense. This effect is driven by an increase in V. gouldii densities near successional edges, which is higher in landscapes that experience extensive human burning. Over time, the positive effects of patch mosaic burning while hunting overwhelm the negative effects of predation in recently burned areas to produce overall positive impacts on lizard populations. These results offer critical insights into the maintenance of animal communities in the desert, supporting the hypothesis that the current high rate of endemic species decline among small animals may be linked to the interaction between invasive species and mid-century removal of Aboriginal niche construction through hunting and patch mosaic burning.

THE DIABLO CANYON FAUNA: A COARSE-GRAINED RECORD OF TRANS-HOLOCENE FORAGING FROM THE CENTRAL CALIFORNIA MAINLAND COAST

Decades ago the Diablo Canyon site (CA-SLO-2) on the central California mainland revealed one of the oldest and longest sequences (ca. 9400 radiocarbon years ago to contact) of coastal occupation on the shore of the northeastern Pacific. The artifacts from these important deposits were reported in detail by Greenwood (1972), but only a fraction of the sites faunal collections was analyzed in the original site report. Acquisition of 30 additional radiocarbon dates and analysis of the complete vertebrate fauna have produced a coarse-grained record of human foraging on the California mainland from 8300 cal B.C. to cal A.D. 1769. The temporally controlled faunal matrix, constituting one of the largest trans-Holocene records from western North America, speaks in a meaningful way to two significant issues in hunter-gatherer prehistory: early Holocene foraging strategies and economic intensification/resource depression over time. The site’s earliest component suggests a population invested in watercraft and intensely adapted to the interface of land and sea along the northeastern Pacific coastline. While boats were used to access offshore rocks, terrestrial mammals (e.g., black-tailed deer) were also of primary importance. Dominance of deer throughout the Diablo occupations is inconsistent with recent generalizations about big-game hunting as costly signaling in western North American prehistory. Diachronic variation, correlated with superimposed burials that show growth in human populations through the Holocene, includes: (1) modest incremental changes in most taxa, suggesting resource stability and increasing diet breadth; (2) gradual but significant variation in a few taxa, including the flightless duck which was hunted into extinction and eventually replaced by sea otters; (3) punctuated, multidirectional change during the late Holocene related to historic contingencies of the Medieval Climatic Anomaly and protohistoric disruptions.

Environmental productivity predicts migration, demographic, and linguistic patterns in prehistoric California

Global patterns of ethnolinguistic diversity vary tremendously. Some regions show very little variation even across vast expanses, whereas others exhibit dense mosaics of different languages spoken alongside one another. Compared with the rest of Native North America, prehistoric California exemplified the latter. Decades of linguistic, genetic, and archaeological research have produced detailed accounts of the migrations that aggregated to build California’s diverse ethnolinguistic mosaic, but there have been few have attempts to explain the process underpinning these migrations and why such a mosaic did not develop elsewhere. Here we show that environmental productivity predicts both the order of migration events and the population density recorded at contact. The earliest colonizers occupied the most suitable habitats along the coast, whereas subsequent Mid–Late Holocene migrants settled in more marginal habitats. Other Late Holocene patterns diverge from this trend, reflecting altered dynamics linked to food storage and increased sedentism. Through repeated migration events, incoming populations replaced resident populations occurring at lower densities in lower-productivity habitats, thereby resulting in the fragmentation of earlier groups and the development of one of the most diverse ethnolinguistic patterns in the Americas. Such a process may account for the distribution of ethnolinguistic diversity worldwide.

Man the showoff? or the ascendance of a jus-so-story: a comment on recent applications of costly signaling theory in American archaeology

In several recent, and highly provocative papers, McGuire and Hildebrandt (Hildebrandt and McGuire 2002, 2003; McGuire and Hildebrandt 2005) have helped introduce costly signaling theory into American archaeology. While their efforts are commendable, we feel that their reinterpretations of western North American prehistory overstate the likely influence of costly signaling on the archaeological record. Only by overlooking a considerable body of ethnographic literature that indicates a more limited role for signaling are they able to characterize Great Basin and California hunters as motivated more by the pursuit of prestige than provisioning. We offer three specific challenges to their models: (1) while McGuire and Hildebrandt treat the issue as decided, the relationships among foraging, provisioning, prestige, and fitness is still actively contested among researchers; (2) while ethnographic studies suggest that some types of hunting and low-return, high-risk activities may indeed represent attempts by males to signal costly behavior, these activities contribute very little to the faunal and other residues that accumulate in the archaeological record; and (3) the theoretical underpinnings of costly signaling explicitly preclude the type of runaway positive feedback loops that Hildebrandt and McGuire implicate as the driving force behind an apparent cultural collapse in the Great Basin at the end of the Middle Archaic.

What Explains Differences in Men’s and Women’s Production?

Researchers commonly use long-term average production inequalities to characterize cross-cultural patterns in foraging divisions of labor, but little is known about how the strategies of individuals shape such inequalities. Here, we explore the factors that lead to daily variation in how much men produce relative to women among Martu, contemporary foragers of the Western Desert of Australia. We analyze variation in foraging decisions on temporary foraging camps and find that the percentage of total camp production provided by each gender varies primarily as a function of men’s average bout successes with large, mobile prey. When men target large prey, either their success leads to a large proportional contribution to the daily harvest, or their failure results in no contribution. When both men and women target small reliable prey, production inequalities by gender are minimized. These results suggest that production inequalities among Martu emerge from stochastic variation in men’s foraging success on large prey measured against the backdrop of women’s consistent production of small, low-variance resources.

People, El Niño southern oscillation and fire in Australia: fire regimes and climate controls in hummock grasslands

While evidence mounts that indigenous burning has a significant role in shaping pyrodiversity, the processes explaining its variation across local and external biophysical systems remain limited. This is especially the case with studies of climate–fire interactions, which only recognize an effect of humans on the fire regime when they act independently of climate. In this paper, we test the hypothesis that an anthropogenic fire regime (fire incidence, size and extent) does not covary with climate. In the lightning regime, positive El Niño southern oscillation (ENSO) values increase lightning fire incidence, whereas La Niña (and associated increases in prior rainfall) increase fire size. ENSO has the opposite effect in the Martu regime, decreasing ignitions in El Niño conditions without affecting fire size. Anthropogenic ignition rates covary positively with high antecedent rainfall, whereas fire size varies only with high temperatures and unpredictable winds, which may reduce control over fire spread. However, total area burned is similarly predicted by antecedent rainfall in both regimes, but is driven by increases in fire size in the lightning regime, and fire number in the anthropogenic regime. We conclude that anthropogenic regimes covary with climatic variation, but detecting the human–climate–fire interaction requires multiple measures of both fire regime and climate. This article is part of the themed issue ‘The interaction of fire and mankind’.