Early human species benefited from food diversity in steep mountainous terrain
image:
Map of Africa and Eurasia showing sites with evidence of human occupation. The inset shows a magnified view of Europe.
view moreCredit: Institute for Basic Science
A new study published in the journal Science Advances [1] by researchers at the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea shows that the patchwork of different ecosystems found in mountainous regions played a key role in the evolution of humans.
A notable feature of the archeological sites of early humans, members of the genus Homo known as hominins, is that they are often found in and near mountain regions. Using an extensive dataset of hominin fossils and artifacts, along with high-resolution landscape data and a 3-million-year-long simulation of Earth’s climate, the team of scientists from ICCP have provided a clearer picture of how and why early humans adapted to such rugged landscapes. In other words, they have helped explain why so many of our evolutionary relatives preferred being “steeplanders” as opposed to “flatlanders.”
Mountainous regions have enhanced biodiversity because the changes in elevation result in shifts of the climate, providing a range of environmental conditions under which different plant and animal species can thrive. The authors showed that steep regions usually exhibit a larger variety and density of ecosystems and vegetation types, known as biomes. Such biome diversity was a draw for early humans, as it provided increased food resources and resilience to climate change, an idea known as the Diversity Selection Hypothesis [2].
“When we analyzed the environmental factors that controlled where human species lived, we were surprised to see that terrain steepness was standing out as the dominant one, even more than local climate factors, such as temperature and precipitation.“ said Elke Zeller, PhD student from the IBS Center for Climate Physics and lead author of the study.
On the other hand, steep regions are more difficult to navigate than flatter terrain and require more energy to traverse. Hominins needed to gradually adapt to the challenges of rougher terrain in order to take advantage of the increased resources. The ICCP researchers examined how, over time, human adaptations changed the cost-benefit balance of living in rugged environments.
The adaptation towards steeper environments (Figs. 1 and 2) is visible for the earliest human species Homo habilis, Homo ergaster, and Homo erectus until about 1 million years ago, after which the topographic signal disappears for about 300,000 years. It reemerges again around 700,000 years ago with the advent of better adapted and more culturally advanced species such as Homo heidelbergensis and Homo neanderthalensis. These groups, which were able to control fire, also exhibited a much higher tolerance for colder and wetter climates.
“The decrease in topographic adaptation around 1 million years ago roughly coincides with large-scale reorganizations in our climate system, known as the Mid-Pleistocene Transition. It also lines up with evolutionary events such as a recently discovered ancestral genetic bottleneck, which drastically reduced human diversity, and the timing of the chromosome 2 merger in hominins. Whether this is all a coincidence, or whether the intensifying glacial climate shifts contributed to the genetic transitions in early humans, remains an open question,” said Axel Timmermann, Director of the IBS Center of Climate Physics and co-author of the study.
How humans have evolved over the past 3 million years and adapted to emerging environmental challenges is a hotly-debated research topic. The results of the South Korean research team provide a new piece in the puzzle of human evolution. Averaged over hundreds of thousands of years, across different species and continents, the data clearly show that our ancestors were “steeplanders.”
“Our results clearly show that over time hominins adapted to steep terrain and that this trend was likely driven by the regionally increased biodiversity. Our analysis suggests that it was beneficial for early human groups to populate mountainous regions, despite the increased energy consumption needed to scale these environments,” said Elke Zeller in summary.
[1] The evolving 3-dimensional landscape of human adaptation, Elke Zeller, Axel Timmermann, Science Advances, doi: 10.1126/sciadv.adq3613, (2024)
[2] Human adaptation to diverse biomes over the past 3 million years, Elke Zeller, Axel Timmermann, Kyung-Sook Yun, Pasquale Raia, Karl Stein and Jiaoyang Ruan, Science, vol. 380, 6645, pp. 604-608, doi: 10.1126/science.abq1288 (2023)
Top: Scatter plot showing time and latitude of sites with evidence of human occupation, middle: biome diversity associated with hominin sites, calculated using a moving average of 15 sites. Bottom: area roughness associated with hominin sites, calculated using a moving average of 15 sites. Gray shading shows the approximate timing of the Mid-Pleistocene Transition (MPT).
Credit
Institute for Basic Science
Journal
Science Advances
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
The evolving 3-dimensional landscape of human adaptation
Article Publication Date
9-Oct-2024
Landscape effects of hunter-gatherer practices reshape idea of agriculture
Indigenous hunter-gatherer practices play key role in plant dispersal, genetic diversity and conservation, according to new research led by Penn State anthropologists
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Solanum diversiflorum (bush tomato) fruit.
view moreCredit: Rebecca Bliege Bird
UNIVERSITY PARK, Pa. — 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.”
Additional contributors to the research include Christopher Martine, Bucknell University; Chloe McGuire, Far Western Anthropological Research Group; Leanne Greenwood, Dja Dja Wurrung Clans Aboriginal Corporation; Desmond Taylor, Martu elder, Kulyakartu Aboriginal Corporation Tanisha Williams, University of Georgia; and Peter Veth, The University of Western Australia. The U.S. National Science Foundation supported this research.
Journal
Nature Communications
Article Title
Seed dispersal by Martu peoples promotes the distribution of native plants in arid Australia
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