Landscape Effects Of Hunter-Gatherer Practices Reshape Idea Of Agriculture

Some of the wild plants that grow across the Australian landscape may not be so wild, according to new research led by Penn State scientists.

The researchers studied four wild Australian plants ­— three test species and one control group — and how the hunting-gathering practices of the Martu Aboriginal people affect where these non-domesticated plants grow on the landscape. They found that the three test species, especially the wild bush tomato, rely on human activity for seed dispersal. The findings, published in Nature Communications, challenge the conventional notion of agriculture and suggest that humans impacted plants’ genetic diversity long before the advent of farming.

“This research is one of the first to show that peoples who are not already engaged in agriculture are still having long-term effects on plant populations,” said Rebecca Bliege Bird, first author of the study and professor of anthropology at Penn State. “In Australia, we’re talking about 50,000 years of Aboriginal involvement with these plants.”

The Martu Aboriginal people have lived in Australia for thousands of years and largely maintained their hunter-gatherer lifestyle to the current day, eschewing the permanency of farming specific crops for their nomadic customs, the researchers explained. Many avoided contact with European settlers and their descendants until the 1960s, when the government removed them from their ancestral lands prior to conducting inter-ballistic missile tests. They began returning to their lands in the 1980s, according to the researchers.

To see how Martu customs and practices affect plant distribution across the landscape, the researchers focused on three edible plants important for sustenance and cultural identity ­— the bush raisin, the bush tomato and love grass, which the Martu winnow and turn into flour. The researchers also looked at the distribution of the fanflower, which is not actively foraged.

The researchers accompanied Martu harvesters on foraging expeditions over a 10-year period and surveyed plants at active and archaeological dinner camp locations where Martu peoples processed and consumed these and other foods. They also used satellite data and ecological surveys to understand the landscape impacts of fires intentionally set by Martu hunters to drive out game. Then they entered the data — like site type, nearest water permanence and fire frequency — into statistical models to see which variables most likely contributed to the presence or absence of the four plants on the landscape.

They found that the three edible plants, especially the bush tomato and love grass, highly depend on both the dispersion of seed and the use of landscape fire for propagation across the landscape. For instance, Martu foragers may taste bush tomatoes while picking the fruit to make sure it’s sweet, discarding the bitter seeds in the bush tomato patch. Or after foraging and transporting the fruit nearer to the community, they may discard the seeds while processing the fruit in bulk around a campfire, explained Bliege Bird. The bush raisin only persists in landscapes where people are actively burning landscape fires for hunting small animals.

“The findings call into question our whole notions of what agriculture is,” said Douglas Bird, study co-author and professor of anthropology at Penn State. “Rather than thinking about the difference between agricultural societies and hunter-gatherer societies as a matter of kind, we’d be better off thinking about it as a matter of degree — that people influence plants long before they engage in what we think of as farming.”

The findings have implications for global conservation efforts of plant and animal species and emphasizes the importance of indigenous involvement in those efforts, according to the researchers.

“In Australia, the importance of an anthropogenic — or human-influenced — landscape for certain species was just critical in the 20th century,” Bliege Bird said. “In addition to promoting the persistence of edible plants, many small native mammals in Australia, especially those in the desert, relied on the anthropogenic fire mosaic. When Aboriginal fire activity was removed, a lot of those small animals went extinct locally or even on a continental scale. Recognizing indigenous involvement in landscapes and ecosystems not only helps us design better conservation policy but contributes to supporting indigenous rights to access land and traditional resources.”