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Study finds environmental conditions influenced how early humans migrated across continents

Study finds environmental conditions influenced how early humans migrated across northern Eurasia and the Americas beyond Africa
The infographic shows the routes most likely favored by the first human migrants across Eurasia and the Americas. These routes are estimated using a statistical combination of archaeological and genetic data. Colored areas indicate the type of ecosystems encountered, based on climate and vegetation models. The inset image illustrates the ideal migration conditions: warm and humid areas containing a mix of forest and grasslands near rivers. Credit: Flinders University

Researchers have gleaned new insights into the great human migration, revealing how environmental conditions in northern Eurasia and the Americas shaped the journey of ancestors who left Africa tens of thousands of years ago.

The Out of Africa theory suggests that more than 70,000 years ago, some groups left Africa to spread across Europe, Asia, Australia, and the Americas. However, it remains unclear how much the environment they encountered beyond Africa facilitated or hindered their journey.

Researchers combined , , and to examine how regional influenced migration and to re-establish our long-lasting connection to nature.

The multidisciplinary analysis, led by Flinders University ecologist Dr. Frédérik Saltré and recently published in Nature Communications, demonstrates that while the relative importance of environmental factors varies across regions, our ancestors traveled primarily through warm and humid areas containing a mix of forest and grasslands near rivers.

"The first human migrants favored routes that provided essential resources and facilitated travel, as well as regions with a mix of forests and open areas for shelter and food, while allowing them to expand into new territories," Dr. Saltré said.

In Europe, humans likely first spread from the Fertile Crescent through the Caucasus Mountains into Scandinavia approximately 48,300 years ago and Western Europe around 44,100 years ago, following warmer and wetter conditions.

In northern Asia, migration routes followed major rivers to cope with harsher climates before reaching Beringia, a currently submerged land bridge between Siberia and Alaska, approximately 34,700 years ago.

In North America, humans initially migrated along the Pacific coast around 16,000 years ago, and then approximately 3,000 years later, moved inland through the ice-free corridor by the Mackenzie River.

In South America, migration followed wetter grasslands bordering the Amazon, leveraging connectivity provided by major rivers by 14,800 years ago.

Professor Tom Higham of the University of Vienna said the power of these new modeling approaches in understanding the deep human past is exciting for archaeological science.

He explained, "For too long we have been working rather separately in our different approaches. Incorporating new modeling methods with the latest climatic, archaeological, and environmental data allows really exciting insights into understanding how ancient humans moved and adapted across vast continents tens of thousands of years ago."

Professor Corey Bradshaw, also from Flinders University and a Chief Investigator at the Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage (CABAH), said modeling provides a powerful framework for exploring and understanding the complexities of deep history, offering insights into how past events and conditions have shaped the present.

He said, "Knowing where people first trekked beyond the cradle of human evolution gives us a flavor of how adaptable our early ancestors were, what environmental challenges they faced, and how they overcame them and survived. We can also infer the technological innovations that were at play during those times—such as watercraft, clothing, and other tools—that allowed people to exploit the most hostile environments."

Associate Professor Bastien Llamas from The University of Adelaide and a Deputy Director in CABAH said merging genetic data with historical climate information and archaeological discoveries is a powerful method for inferring past human migration patterns.

He said, "Studying genetic differences between groups of people helps us understand ancient migration patterns. Typically, this results in a basic map showing general movements from one area to another without detailed routes. However, by combining genetic data with information about past climates, environments, and archaeological findings, we can create much more detailed and accurate maps of how people moved over time and across different regions."

Dr. Saltré said the study's results help us appreciate the importance of biodiversity in how our ancestors adapted to and overcame environmental challenges.

He added, "It underscores how climate and ecology shaped human prehistory, highlighting biodiversity's role in human survival and mobility, demonstrating that rich ecosystems enabled humans to thrive in new environments for thousands of years. The biodiversity crisis that we are experiencing now compromises our ability to thrive. Despite the advanced technology we have today, I genuinely wonder if we will last long without maintaining the bulk of current biodiversity."

More information: Frédérik Saltré et al, Environmental conditions associated with initial northern expansion of anatomically modern humans, Nature Communications (2024). DOI: 10.1038/s41467-024-48762-8

Journal information: Nature Communications

Citation: Study finds environmental conditions influenced how early humans migrated across continents (2024, May 29) retrieved 15 June 2024 from
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