Saudi Arabia Rewrites the History of Humanity

by Dr. Iyad Saleh A. Zalmout

Scientists earlier thought that our species (Homo sapiens) left Africa through the Levant (Palestine, Jordan, Lebanon, and Syria) and migrated to Eurasia about 60 kya (Fig. 1). This was based on molecular and biological analyses of the recent DNA data, or what is called the Molecular Clock. However, recent paleontological and geological research that the Saudi Geological Survey took part in, resulted in new discoveries out of the valuable data that were gathered from the Nafud Desert in northwestern Saudi Arabia. These discoveries have been astonishing, because they push back the timeline for the early human migration and expansion in the region back to 20 kya (or may be more), earlier than what was estimated. The results of the findings were published in Nature Ecology & Evolution (DOI: 10.1038/s41559-018-0518-2 (Published online: 09 April 2018).

Migration map and the oldest confirmed records of Homo sapiens from Africa and Arabia, including the new record from the Al-Wusta locality of the Nafud Desert in Saudi Arabia. (The Times/Monday April 9, 2018, page 13)

The updated information is based on a single finger bone that was identified as a middle intermediate phalanx (Fig. 2 and 3), and it resembles those found in the hands of Homo sapiens. It was found in the Late Pleistocene–Holocene freshwater paleolake sediments in the sand dunes of the Nafud Desert (Fig. 4). The fossil locality, from where this precious fossil was excavated, is called Al Wusta paleolake. It is about 140 km east of the Tayma Governorate, Tabuk Province, in the northwestern part of Saudi Arabia. This remote and secluded locality in the Nafud Desert became a landmark on the world map that assigns Saudi Arabia as a game player in the paleobiogeographic distribution of the early members of our species. Numerous animal fossils, including those of a hippopotamus and tiny fresh water snails, were found at the site, as well as abundant stone tools that were made by the early humans.

Field photo of the finger bone fossil on the palm of one of the members of the exploration crew. (Photo by Saudi Geological Survey).


Finger bone fossils of Homo sapiens from the Al-Wusta site, Saudi Arabia. (Photo credit: Ian Cartwright).

Al-Wusta paleolake locality in the Nafud Desert, northwestern Saudi Arabia. (Picture by Richard Clark-Wilson).

This fossil represents the first direct evidence from Homo sapiens that lived in Saudi Arabia at (or before) 85 kya. This is the oldest directly dated fossil of our species outside Africa and the Levant.

The previously confirmed published reports about the fossil records of Homo sapiens show that Africa cradled the oldest members of this species (Fig. 1). A 315-ky old jaw bone and other cranial elements that were discovered in Jebel Irhoud in Morocco were confirmed and assigned to Homo sapiens. This is the oldest record of the dispersal of Homo sapiens on earth. Between 260 kya and 160 kya the species reached southern and eastern Africa and the Levant. Land masses (bridges or corridors) and climatic fluctuations drove the early members of the species out of Africa towards the Levant to search for new hunting grounds and lusher green places that were grazed by mammals and had a high potential as a source of food.

Back to the core of this article, the fossilized finger bone has almost a wedge shape, and is gracile, less robust, compressed dorsoventrally. Its proximal side forms a shallow socket, and its distal end is protruding forward. It is less than 33 mm long, with a maximum proximal width of 15 mm and a proximal height of 9 mm. The morphology and landmarks of the bone are very well preserved and enabled the international team of scientists, who ran the morphological analysis, to assign this bone to our species. At least 200 phalanges of human and non-human primates were compared against the Nafud finger bone by conducting linear geometric and morphometric analyses (GMM). The analyses showed that there is an overlap of the shape and size of this new fossil with the other phalanges of the other taxa. However, the gracile bone is consistent with the shape and size (within the range of variations) of the counterpart phalanges of the recent and early members of Homo sapiens. The morphology of the fossil finger bone may reflect the high and varied loading of the fingers during intense manual activities, such as during hunting and manufacturing of stone tools.

The age determination of the fossils took place at high caliber laboratories in England and Australia. Experts have used three new methods to gain the age control of the fossil. The first method is known as the OSL (Optically Stimulated Luminescence) for the sediments, which dates the last day of the exposure of the animal to the sun. The second is known as the U-series )Uranium Series: the amount of uranium intake of the newly deceased body or fossilized elements from the sediments during and after burial), the amount of the U isotopes was then converted into various proxies to fit the frame and equations used in the age inquiry. Finally, the Electron Spin Resonance (ESR) was used here to support the OSL and the U-series methods. The ESR mostly depends on measuring the amount of the trapped radicals (alpha, beta, and gamma particles) within the lattices or the structure of a crystal or mineral. The established ages from these three methods were curved and averaged. The measured age for the finger bone is at least 85 kyr.

Dating the fossil bone at 85 kyr assigns the Al Wusta site to fall within the range of late MIS5 (Marine Isotope Stage 5). This corresponds to a humid phase in the historical interval that is associated with the drastic drop in sea level. This explains the significant aspects of this dispersal process, being facilitated by enhanced monsoonal rainfall, and more lands were exposed from the drop in global sea level. While changes in the behavior and demography are crucial to the understanding of the dispersal process, climatic windows of opportunity were also key in allowing Homo sapiens to cross the Sahara-Arabian arid belt, which often constituted a formidable barrier to migration.

But why is this discovery very important? This is the first fossil record of Homo sapiens with lengthy history that was found in the Arabian Peninsula. It expands across the historical map and assigns new routes that the early members of Homo sapiens had considered for migration to seek moderate weather and enough food.

After this discovery, expectations are very high to find more fossil remains of the early members of Homo sapiens that are preserved in or near the Al-Wusta lake deposits of the Nafud Desert. Finding the level from which the fossil came from is a great potential for future fieldworks. There is a big chance for more remains to be found from the earlier fresh water lakes and from the later ones that are younger than the Al-Wusta. Across the Nafud Desert, thousands of freshwater lakes, now dried-up, are perfectly exposed. They are varied in age, size, and thickness. These paleolakes and deposits may hold answers to the mysteries of early migration and the behavior of the early inhabitants of humankind.

The Saudi Geological Survey, with all of its professional assets, is always upfront in paleontological explorations that result in new discoveries, enrichening the Saudi Arabian heritage and natural history.

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The results of this research was published in Nature Ecology & Evolution, DOI: 10.1038/s41559-018-0518-2 (Published online: 09 April 2018)

Homo sapiens in Arabia by 85,000 years ago

by Huw S. Groucutt, Rainer Grün, Iyad S. A. Zalmout, Nick A. Drake, Simon J. Armitage, Ian Candy, Richard Clark-Wilson, Julien Louys, Paul S. Breeze, Mathieu Duval, Laura T. Buck, Tracy L. Kivell, Emma Pomeroy, Nicholas B. Stephens, Jay T. Stock, Mathew Stewart, Gilbert J. Price, Leslie Kinsley, Wing Wai Sung, Abdullah Alsharekh, Abdulaziz Al-Omari, Muhammad Zahir, Abdullah M. Memesh, Ammar J. Abdulshakoor, Abdu M. Al-Masari, Ahmed A. Bahameem, Khaled S. M. Al Murayyi, Badr Zahrani, Eleanor M. L. Scerri, and Michael D. Petraglia