Early humans and their hominin relatives had to adapt to new environments to spread out of Africa. In a new study, paleoanthropologists from the Institute for Basic Science, Pusan National University and elsewhere explored the movements of hominins across and preferences for different biomes by comparing six Homo species distributions from the fossil record against simulated climate and vegetation over the past 3 million years. They found that some later species inhabited a broader range of biomes as they spread to colder and more forested areas, especially Homo sapiens, which settled in more extreme habitats (deserts and tundra).
An artist’s illustration of hominins arriving in a multi-biome mosaic landscape. Image credit: Center for Climate Physics, Institute for Basic Science.
Homo sapiens are the only surviving hominin species today.
However, whether this is because our species was uniquely successful at adapting to Pleistocene environments, because we outcompeted other contemporary Homo species through unique physiological or social adaptations, or because we simply outlived others by chance remains largely unknown.
Although challenging to understand, the connection between hominins and their ecological environment, particularly how Homo species adapted to environmental change and extremes and how this affected survival and migration from Africa and into Eurasia, is central to finding these answers.
“Our genus Homo evolved over the past 3 million years — a period of increasing warm/cold climate fluctuations,” said lead author Elke Zeller, a Ph.D. student at the Institute for Basic Science and Pusan National University, and colleagues.
“How early human species have adapted to the intensification of climate extremes, ice ages, and large-scale shifts in landscapes and vegetation remains elusive.”
“Did our ancestors adjust to local environmental changes over time, or did they seek out more stable environments with diverse food resources?”
“Was our human evolution influenced more by temporal changes in climate, or by the spatial character of the environment?”
To test these fundamental hypotheses, the authors used a compilation of more than 3,000 well-dated human fossil specimens and archaeological sites, representing six different Homo species, in combination with realistic climate and vegetation model simulations, covering the past 3 million years.
They focused on biomes — geographic regions which are characterized by similar climates, plants, and animal communities (e.g., savannah, rainforest, or tundra).
“For the archeological and anthropological sites and corresponding ages, we extracted the local biome types from our climate-driven vegetation model,” Zeller said.
“This revealed which biomes were favored by the extinct hominin species Homo ergaster, Homo habilis, Homo erectus, Homo heidelbergensis, and Homo neanderthalensis and by our direct ancestors — Homo sapiens.”
The researchers found that earlier African groups preferred to live in open environments, such as grassland and dry shrubland.
Migrating into Eurasia around 1.8 million years ago, hominins, such as Homo erectus and later Homo heidelbergensis and Homo neanderthalensis developed higher tolerances to other biomes over time, including temperate and boreal forests.
“To survive as forest-dwellers, these groups developed more advanced stone tools and likely also social skills,” said Professor Pasquale Raia, a researcher at the Università di Napoli Federico II.
“Eventually, Homo sapiens emerged around 200,000 years ago in Africa, quickly becoming the master of all trades.”
“Mobile, flexible, and competitive, our direct ancestors, unlike any other species before, survived in harsh environments such as deserts and tundra.”
When further looking into the preferred landscape characteristics, the scientists found a significant clustering of early human occupation sites in regions with increased biome diversity.
“What that means is that our human ancestors had a liking for mosaic landscapes, with a great variety of plant and animal resources in close proximity,” said Professor Axel Timmermann, director of the Center for Climate Physics at the Institute for Basic Science and a researcher at Pusan National University.
“The results indicate that ecosystem diversity played a key role in human evolution.”
The study was published in the journal Science.
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Elke Zeller et al. 2023. Human adaptation to diverse biomes over the past 3 million years. Science 380 (6645): 604-608; doi: 10.1126/science.abq1288
