In a history-changing discovery, a group of scientists has recently published a study detailing among other things, how our ancestors left Africa 100,00 years sooner than previously thought and migrated into a green Arabian Peninsula.
Scientists have explained that the first dispersion of hominins beyond Africa did not imply adaptations to environmental extremes, such as arid and hard deserts such as those that extend today in the Arabian Peninsula.
The discovery of stone tools and cutting marks on the remains of animal fossils excavated at the site of Ti Ghadah provides definitive evidence of hominins in Saudi Arabia at least 100,000 years earlier than previously known.
This is according to a new study led by scientists from the Max Planck Institute for the Science of Human History, and published in ‘Nature Ecology and Evolution’.
“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 dispersal of our archaic ancestors were part of a range expansion rather than a result of novel adaptations to new environmental contexts outside Africa.”
Studies of early and late dispersal of hominin populations beyond Africa are important in understanding the course of global human evolution and what it means to be human.
Although the species that make up the genus ‘Homo’ are often called ‘human’ in academic and public discourse, this evolutionary group (or genus), which emerged in Africa about 3 million years ago, is very diverse.
In fact, there is an ongoing debate about the extent to which our own species ‘Homo sapiens’, which emerged in Africa about 300,000 years ago, showed a unique ecological plasticity to adapt to novel environments compared to other members of the ‘Homo’ genre.
Recently, it has been argued that the first ‘Homo sapiens’ occupied a diversity of extreme environments, including deserts, rain forests, arctic and high-altitude areas, all over the world, effectively changing what we thought we knew about our ancestors.
In contrast, the dispersion of other earlier and contemporary ‘Homo’ species, such as Neandertals, seem to be associated with the widespread use of different mosaics of forests and grasslands in and between river and lake environments.
However, the lack of paleoenvironmental data has made systematic testing of this idea difficult and, in fact, several researchers maintain that species that are not ‘Homo sapiens’ demonstrate an adaptive cultural and ecological flexibility.
Despite its crucial geographical position at the crossroads between Africa and Eurasia, the Arabian Peninsula has been surprisingly absent from discussions about the first human expansions until recently.
However, studies of climate models, cave records, lake records, as well as animal fossils have shown that at certain points in the past, the severe and hyper-arid deserts that cover much of Arabia today were replaced by much greener conditions that would have represented an attractive scenario for several populations of hominins.
For the study, scientists 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 discovered an ample selection of 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, Ph.D. 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.”
However, until recently, 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.”