Early humans adapted to mosaic landscapes to survive climate change

A recent study published in the prestigious journal Science, conducted by an international team, sheds new light on the adaptive strategies of early human species in response to changing climates. The research suggests that our ancestors, belonging to the Homo genus, successfully thrived in mosaic landscapes with diverse food resources, which enhanced their resilience to climatic shifts throughout the past 3 million years.

Understanding how early humans coped with the intensification of climate extremes, ice ages, and transformations in landscapes and vegetation has long remained a mystery. The study aims to address key hypotheses regarding human evolution and adaptation, specifically whether our ancestors gradually adapted to local environmental changes or actively sought out more stable environments rich in varied food sources. Additionally, the researchers aimed to determine whether temporal changes in climate or the spatial characteristics of the environment had a greater influence on human evolution.

To quantitatively test these hypotheses, the research team employed an extensive dataset consisting of over three thousand well-dated human fossil specimens and archaeological sites, spanning six distinct human species. This wealth of information was combined with sophisticated climate and vegetation model simulations, covering a time span of 3 million years. The scientists focused their analysis on biomes, which are geographical regions characterized by similar climates, plants, and animal communities, such as savannahs, rainforests, or tundras.

By cross-referencing the archaeological and anthropological sites with the corresponding ages, the researchers extracted the local biome types using a climate-driven vegetation model. This allowed them to determine the preferred biomes of extinct hominin species such as H. ergaster, H. habilis, H. erectus, H. heidelbergensis, H. neanderthalensis, as well as our direct ancestors, H. sapiens. Elke Zeller, a Ph.D. student from the IBS Center for Climate Physics at Pusan National University in South Korea, and the lead author of the study, explained the significance of their findings.

The study’s findings have profound implications for our understanding of human evolution and adaptation throughout history. They highlight the remarkable ability of early human species to adapt and thrive in diverse environments, demonstrating their resilience in the face of changing climates. These insights contribute to our broader knowledge of how our ancestors navigated environmental challenges and provide valuable context for the development of our species, Homo sapiens.

Timeline of hominin evolution and adaptation to various vegetation types. According to the new Science study, adaptation played a key role in the geographic expansion of our genus Homo. Credit: Elke Zeller. This work includes adapted images from HCRP-UR501 and Sangiran 17 by Gerbil, Bodo by Ryan Somma, and Daka Homo by Cretan used under CC BY 3.0 and DNH-134 from Herries, A.I.R. et al. Science 2020.

The scientists’ analysis revealed that earlier African groups exhibited a preference for living in open environments, such as grasslands and dry shrublands. As hominins migrated into Eurasia around 1.8 million years ago, species like H. erectus, H. heidelbergensis, and H. neanderthalensis gradually developed increased tolerances for various biomes, including temperate and boreal forests.

Professor Pasquale Raia from the Università di Napoli Federico II in Italy, a co-author of the study, explained that these groups had to adapt to survive as forest-dwellers, leading to the development of more advanced stone tools and likely the acquisition of social skills. Approximately 200,000 years ago, H. sapiens emerged in Africa and quickly became highly adaptable, mobile, and competitive. Unlike any species before, our direct ancestors thrived in challenging environments such as deserts and tundra.

When investigating the preferred characteristics of landscapes, the researchers observed a notable concentration of early human occupation sites in regions with greater biome diversity. Professor Axel Timmermann, Director of the IBS Center for Climate Physics in South Korea and a co-author of the study, explained that this indicates our human ancestors had a preference for mosaic landscapes—areas with a wide variety of plant and animal resources in close proximity. The results suggest that ecosystem diversity played a crucial role in human evolution.

For the first time on continental scales, the authors demonstrated this preference for mosaic landscapes, proposing a new hypothesis known as Diversity Selection Hypothesis. According to this hypothesis, Homo species, especially H. sapiens, possessed unique abilities to exploit diverse biomes.

Elke Zeller emphasized the importance of landscape and plant diversity as selective factors for humans and potential drivers for socio-cultural developments. The study sheds light on how shifts in vegetation have shaped human sustenance, providing unprecedented insights into human prehistory and survival strategies.

The climate and vegetation model simulations, encompassing the Earth’s history over the past 3 million years, were carried out on Aleph, one of South Korea’s high-performance supercomputers. Professor Axel Timmermann stated that supercomputing is emerging as a vital tool in the fields of evolutionary biology and anthropology.

Source: Institute for Basic Science

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