A recent study reveals that the diverse ecosystems found in mountainous areas significantly influenced human evolution.
A recent publication in the journal Science Advances, conducted by researchers from the IBS Center for Climate Physics (ICCP) at Pusan National University in South Korea, indicates that the variety of ecosystems in mountainous regions was vital to the evolution of humans.
One significant observation regarding the archeological sites of early humans, classified under the genus Homo, is their common presence in or near mountainous areas. By utilizing a comprehensive dataset of hominin fossils and artifacts, alongside high-resolution landscape data and a 3-million-year climate simulation, the ICCP scientists have shed light on how early humans adapted to challenging terrains. Essentially, they have clarified why many of our evolutionary ancestors favored living in steep areas instead of flat ones.
Mountainous regions boost biodiversity due to elevation changes, which lead to varying climates, allowing different plant and animal species to flourish. The researchers discovered that steep areas typically host a greater variety and density of ecosystems and types of vegetation, known as biomes. This richness in biomes attracted early humans by offering more food resources and better resilience to climate fluctuations, a concept referred to as the Diversity Selection Hypothesis.
“During our analysis of the environmental elements influencing human habitats, we were surprised to find that terrain steepness emerged as the most significant factor, surpassing local climate variables like temperature and rainfall,” explained Elke Zeller, a PhD student from the IBS Center for Climate Physics and the study’s lead author.
Conversely, steep terrains are harder to navigate compared to flat areas and demand more energy to cross. Hominins had to gradually adapt to the challenges posed by rough landscapes to utilize the added resources effectively. The ICCP researchers studied how human adaptations shifted the energy cost versus benefits of living in such environments over time.
The tendency to adapt to steeper surroundings is evident in the earliest human species such as Homo habilis, Homo ergaster, and Homo erectus until about a million years ago, after which this trend diminished for approximately 300,000 years. It reemerged around 700,000 years ago with the rise of better-adapted and more culturally advanced species, including Homo heidelbergensis and Homo neanderthalensis. These groups had control over fire and demonstrated a greater ability to withstand colder and wetter climates.
“The reduction in adaptation to topography around one million years ago coincides with significant reorganizations in our climate system known as the Mid-Pleistocene Transition. This period also corresponds with evolutionary milestones, such as a recently identified ancestral genetic bottleneck that significantly lowered human diversity and the merging of chromosome 2 in hominins. It’s still uncertain whether these events are merely coincidental or if the increasing glacial climate changes contributed to the genetic evolution in early humans,” stated Axel Timmermann, Director of the IBS Center of Climate Physics and co-author of the study.
The ongoing debate regarding how humans have evolved over the last 3 million years in response to environmental challenges is a significant research topic. The findings from this South Korean research team contribute an important piece to the complex puzzle of human evolution. Data, averaged over hundreds of thousands of years across various species and continents, suggests that our ancestors were indeed inclined towards steep terrains.
“Our findings clearly indicate that over the years, hominins adapted to steep landscapes, likely driven by the enhanced biodiversity in these regions. Our analysis implies that despite the increased energy expenditures required to navigate these areas, it was advantageous for early human groups to inhabit mountainous zones,” summarized Elke Zeller.
