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A new study, led by scientists from UNSW Sydney and published in Nature Ecology and Evolution today, suggests that early hominin dispersals beyond Africa did not have to adapt to environmental extremes, such as to arid and harsh deserts.

For the study, the researchers undertook renewed archaeological excavations and analysis of fossil fauna found at the site of Ti’s al Ghadah, in the Nefud Desert of northern Saudi Arabia. The scientists found stone tools and cut-marks on fossil animal remains that indicate the presence of our ancestors 500,000 to 300,000 years ago. The discovery of these tools and remains shows that hominins were present in Saudi Arabia at least 100,000 years earlier than previously known.

“Ti’s al Ghadah is one of the most important palaeontological sites in the Arabian Peninsula,” UNSW lead author, PhD candidate Mathew Stewart, explains.

“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.”

Until now, however, the absence of stone tools has made linking these animals with early hominin presence uncertain.

“Our discoveries make 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,” says Michael Petraglia from the Max Planck Institute for the Science of Human History, the principal archaeologist of the project and a co-author on the paper.

UNSW author Mathew Stewart adds: “In spite of its crucial geographic position at the crossroads between Africa and Eurasia, the Arabian Peninsula has been astoundingly absent from discussions about early human expansions until recently.

“However, recent analysis of climate models, cave records, lake records, and animal fossils have shown that at certain points in the past, the harsh, hyper-arid deserts that cover much of Arabia today were replaced by ‘greener’ conditions that would have represented an attractive setting for various hominin populations.”

Stable isotope analysis of fossil animal reveals that the Arabian Peninsula was dominated by grassland vegetation at certain points in the past, with aridity levels similar to those found in open savanna settings in eastern Africa today. This indicates that early dispersals of our archaic ancestors were part of a range expansion rather than a result of novel adaptations to new environmental contexts outside Africa.

Lead author Dr Patrick Roberts from Max Planck Institute for the Science of Human History says that “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.

“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.”

More detailed study of past environments, closely associated with different forms of hominin species in the Arabian Peninsula and elsewhere, should enable more refined testing as to whether our species is uniquely flexible in terms of its adaptations to varying environments. 


Title: Fossil herbivore stable isotopes reveal Middle Pleistocene hominin palaeoenvironment in ‘Green Arabia’

Authors: Patrick Roberts, Mathew Stewart, N Aziz, Paul Breeze, Ian Candy, Nick Drake, Huw S. Groucutt, Eleanor M.L. Scerri, Julia Lee-Thorp, Julien Louys, Iyad S. Zalmout, Yahya S. A. Al-Mufarreh, Jana Zech, Abdullah M. Alsharekh, Abdulaziz al Omari, Nicole Boivin, Michael Petraglia

Publication: Nature Ecology and Evolution