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The earliest hominins were migrating to expand their range

A new study led by experts at the Max Planck Institute for the Science of Human History suggests that early hominin migrations beyond Africa did not involve adaptations to climate extremes. The new data suggests that our early ancestors dispersed in order to expand their ranges, and not to adapt to new environmental conditions.

The researchers have found clear evidence, including stone tools and cut-marks on fossilized animal remains, that hominins settled in Saudi Arabia at least 100,000 years earlier than previously known.

“While these early hominin populations may have possessed significant cultural capacities, their movement into this part of the world would not have required adaptations to harsh and arid deserts,” explained study lead author Dr. Patrick Roberts. “Indeed, the isotope evidence suggests that this expansion is more characteristic of a range expansion similar to that seen among other mammals moving between Africa, the Levant, and Eurasia at this time.”

To understand human evolution, it is also important to understand the early and late dispersals of hominin populations beyond Africa. While the species that make up the genus Homo are often referred to as “human,” this evolutionary group – which emerged in Africa around three million years ago – is highly diverse.

Our own species, Homo sapiens, emerged in Africa around 300,000 years ago. The extent to which our species was able to adapt to new environments compared to other hominin members of the genus Homo is still up for debate.

Image Credit: Palaeodeserts Project (Ian R. Cartwright)

Some experts have recently argued that early Homo sapiens occupied a diverse range of extreme environments around the world, including deserts, tropical rainforests, the arctic, and high-altitude settings. By contrast, earlier Homo species are believed to have stuck close to grasslands and forests in and around lakes and rivers.

A lack of data has made it difficult to test this idea, and some researchers believe that non-Homo sapiens species were much more flexible and adaptable.

For the current study, the researchers focused on the archaeological excavations and analysis of fossil fauna found at the site of Ti’s al Ghadah, in the Nefud Desert of northern Saudi Arabia.

“Ti’s al Ghadah is one of the most important palaeontological sites in the Arabian Peninsula and it currently represents the only dated collection of middle Pleistocene fossil animals in this part of the world, and includes animals such as elephant, jaguar and water birds,” said study co-author Mathew Stewart.

Until now, the lack of stone tools has made it difficult to link these animals with early hominins. In this study, the research team found stone tools alongside evidence for the butchery of animals on bones, confirming a hominin presence with these animals 500,000 to 300,000 years ago.

Michael Petraglia is the principal archaeologist of the project and a co-author on the paper.

“This makes Ti’s al Ghadah the first, early hominin-associated fossil assemblage from the Arabian Peninsula, demonstrating that our ancestors were exploiting a variety of animals as they wandered into the green interior,” explained Petraglia.

A stable isotope analysis of the fossils indicates that they originated in a predominantly grassland region, which had aridity levels similar to those found in the open savanna of eastern Africa today.

Further research, including detailed studies into our past environments, is still needed to test whether our species is uniquely flexible in our ability to adapt to extreme environments.

The study is published in the journal Nature Ecology & Evolution.

By Chrissy Sexton, Staff Writer

Image Credit: Palaeodeserts Project (Klint Janulis)

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