Human ancestors preferred mosaic landscapes with diverse ecosystems

A recent study that casts light on early human species’ adaptation to varying landscapes and diverse food resources has been published in journal Science. The research indicates that such adaptations may have boosted our ancestors’ resilience to past climate shifts.

Our genus, Homo, has evolved over the past three million years, a timeline marked by increasingly intense fluctuations between warm and cold climates. Yet, the mechanisms by which early human species adapted to intensifying climate extremes, ice ages, and large-scale shifts in landscapes and vegetation have remained a mystery. 

Did our ancestors evolve to cope with local environmental changes over time, or did they migrate to environments that were more stable and rich in food resources? What influenced human evolution more – temporal changes in climate or the spatial characteristics of the environment?

How the study was done

Aiming to answer these fundamental questions on human evolution and adaptation, the research team used a vast compilation of over 3,000 well-dated human fossil specimens and archeological sites. These sites represent six different human species and are combined with accurate climate and vegetation model simulations covering the past three million years.

Elke Zeller is a Ph.D. student from the IBS Center for Climate Physics at Pusan National University, South Korea and the lead author of the study. “For the archeological and anthropological sites and corresponding ages, we extracted the local biome types from our climate-driven vegetation model. This revealed which biomes were favored by the extinct hominin species H. ergaster, H. habilis, H. erectus, H. heidelbergensis, and H. neanderthalensis and by our direct ancestors – H. sapiens,” explained Zeller.

Biomes – geographical regions defined by similar climates, plants, and animal communities, like the savannah, rainforest, or tundra – were at the center of the scientists’ analysis. 

What the researchers learned

Their findings suggest that earlier African groups had a preference for open environments such as grassland and dry shrubland. However, when hominins like H. erectus and later H. heidelbergensis and H. neanderthalensis migrated into Eurasia around 1.8 million years ago. There, they developed higher tolerances to other biomes, including temperate and boreal forests.

Study co-author Professor Pasquale Raia from the Università di Napoli Federico II noted: “To survive as forest-dwellers, these groups developed more advanced stone tools and likely also social skills.” 

This adaptation culminated with the emergence of H. sapiens approximately 200,000 years ago in Africa. Unlike any other species before, our direct ancestors proved to be mobile, flexible, and competitive, surviving in harsh environments such as deserts and tundra.

The experts found a significant clustering of early human occupation sites in regions with increased biome diversity. 

Professor Axel Timmermann, director of the IBS Center for Climate Physics, explained: “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.” This highlights the pivotal role ecosystem diversity played in human evolution.

Why this study is important

For the first time on continental scales, the authors demonstrated this preference for mosaic landscapes and proposed a new Diversity Selection Hypothesis: Homo species, especially H. sapiens, were uniquely equipped to exploit heterogeneous biomes.

“Our analysis shows the crucial importance of landscape and plant diversity as a selective element for humans and as a potential driver for socio-cultural developments,” said Zeller.

The study offers a unique perspective into human prehistory and survival strategies, showing how vegetation shifts have influenced human sustenance.

The comprehensive climate and vegetation model simulations, which span the Earth’s history of the past 3 million years, were carried out on Aleph, one of South Korea’s fastest science supercomputers. The research emphasizes the integral role of supercomputing in evolutionary biology and anthropology.

“Supercomputing is now emerging as a key tool in evolutionary biology and anthropology,” said Timmermann.

The study, therefore, not only elucidates how our ancestors adapted and thrived in shifting environments but also underlines the importance of cutting-edge technology in revealing the intricacies of human evolution.

Overall, the research offers unprecedented insights into how our ancestors adapted to the world around them. By understanding our past, we can better comprehend our present and future as a species. 

The study also serves as a stark reminder of the deep and enduring connection between humans and their environment, a connection that continues to shape our lives today. The more we learn about our past, the better equipped we are to navigate the challenges of the future.

What Earth was like 3 million years ago

Three million years ago, during the Pliocene Epoch, which spans from about 5.3 to 2.6 million years ago, Earth was significantly different from what it is today. Here’s a summary of the key characteristics of that period:

Climate

The Pliocene was a time of global warmth compared to the periods preceding and following it. Average global temperatures were estimated to be about 2 to 3 degrees Celsius higher than today, and the Arctic, in particular, was significantly warmer, potentially by as much as 10 degrees Celsius. This led to smaller polar ice caps and higher global sea levels, possibly up to 25 meters higher than present day.

Flora and Fauna

The warmer Pliocene climate supported a diverse array of life forms. On land, coniferous forests and grasslands were widespread. This was also the time when grasslands and savannas started to become more common, especially in Africa, which had a significant impact on the evolution of early human ancestors.

Marine life was also diverse, with the warmer seas supporting a range of species. However, towards the end of the Pliocene, as the Earth started to cool, there was a major extinction of marine species.

Geography

The continents were roughly in the positions we know them to be today, but they were still moving into their present locations. The Isthmus of Panama, for example, was newly formed, connecting North and South America and significantly altering ocean currents and the global climate.

Early Hominins

This was a significant period for human evolution. In Africa, our early hominin ancestors were becoming more adept at walking upright. Species like Australopithecus afarensis show evidence of bipedalism. 

The development of stone tool technology also possibly began during this time, although the oldest definitive evidence of tool use is from about 2.6 million years ago, towards the very end of the Pliocene.

Please note that our understanding of geological epochs is continually refined as new evidence comes to light, so future research may alter our understanding of the Pliocene.

Image Credit: Institute for Basic Science

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