NEWS - Researchers at the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea suggest that the patchwork of ecosystems found in mountainous regions played a key role in human evolution.
Using a vast dataset of fossils, artifacts, high-resolution landscapes and 3 million-year-long simulations of Earth’s climate, a team of scientists is painting a clearer picture of how and why early humans adapted to rugged landscapes.
Hominins are often found in and near mountainous regions. Now Elke Zeller and Axel Timmermann have helped explain why so many of our evolutionary relatives preferred to be “highlanders” rather than “lowlanders.”
Mountainous regions are rich in biodiversity, providing a range of environmental conditions in which different species of plants and animals thrive. Steep areas typically exhibit a greater diversity, density of ecosystems and vegetation types, known as biomes.
This diversity of biomes was attractive to early humans because it provided more food resources and resilience to climate change, an idea known as the Diversity Selection Hypothesis.
“When we analyzed the environmental factors that controlled the habitation of the human species, we were surprised to see that the steepness of the terrain stood out as the dominant factor, even more so than local climatic factors, such as temperature and precipitation,” says Elke Zeller.
On the other hand, steep terrain is more difficult to navigate and requires more energy to traverse. Hominins needed to gradually adapt to steeper challenges in order to take advantage of increasing resources. Over time, human adaptation changed the cost-benefit balance of living in steep environments.
Adaptation to steeper environments was seen in the earliest human species Homo habilis, Homo ergaster and Homo erectus until about 1 million years ago, after which the topographic signal disappeared for about 300,000 years.
Around 700,000 years ago, better adapted and more culturally advanced species such as Homo heidelbergensis and Homo neanderthalensis emerged. These groups were able to control fire and showed a much higher tolerance for colder and wetter climates.
“The decline in topographic adaptation around 1 million years ago roughly coincides with a large-scale reorganization in the climate system known as the Mid-Pleistocene Transition. It also coincides with evolutionary events such as the ancestral genetic bottleneck that drastically reduced human diversity, and the timing of the hominin chromosome 2 merger,” says Axel Timmermann.
“Whether this was all just a coincidence or whether increasingly intense glacial climate shifts contributed to the genetic transition in archaic humans is still an open question,” says Timmermann.
How humans evolved over the past 3 million years and adapted to emerging environmental challenges is a hotly debated topic. A South Korean research team provides a new piece in the human evolutionary puzzle. Data spanning hundreds of thousands of years across multiple species and continents clearly show that our ancestors were highlanders.
“Hominins adapted to steep terrain and this trend was likely driven by increasing biodiversity in the region. We show that it was advantageous for archaic human groups to inhabit mountainous areas, despite the increased energy consumption involved,” says Zeller.
Original research
Elke Zeller, Axel Timmermann, The evolving three-dimensional landscape of human adaptation. Science Advances, 10, eadq3613 (2024), DOI:10.1126/sciadv.adq3613
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