On a cold, windy day in February 1985, in a broad canyon in northern Saudi Arabia surrounded by high escarpments, two men walked slowly across the terrain, stooping occasionally to pick up stones from the ground.
They were American archeologists from Texas who had gone to the canyon to investigate an ancient site discovered eight years earlier. A few miles to the northeast, one could see the faint outline of the small village of Shuwayhitiyah, where these men and their Saudi colleagues had set up camp a few days before. As they walked along, intently searching the ground for artifacts, the archeologists commented on their good fortune: The stone artifacts they were collecting - man-made tools - were among the oldest ever found in Asia. With a feeling of awe, they realized that most, and perhaps all, of these artifacts had not been touched by human hands since their original makers discarded them, more than a million years in the past.
The archeological site of Shuwayhitiyah is the oldest found to date in Saudi Arabia. The 1517 separate artifacts that the binational team of archeologists removed from the site belonged to an early stone-tool tradition called the Developed Oldowan, first identified by Louis and Mary Leakey at their enormously productive digs at Olduvai Gorge, across the Red Sea in Tanzania. The age of the tools - choppers, polyhedrons, spheroids and discoids - exceeded one million years. The site, in the shape of a horseshoe almost five kilometers (three miles) long, consisted of 16 concentrations of artifacts separated by distances of 200 to 350 meters (700 to 1200 feet). The artifacts were made from quartzite, a granular form of quartz, that had eroded down from the top of the escarpments that overlooked the site.
At the southern end of the kingdom of Saudi Arabia, hundreds of kilometers southwest of Shuwayhitiyah, lies the Saudi town of Najran. In 1980, an archeological survey team gathered a small collection of 34 stone tools from a wadi near the town. They, too, were made from quartzite and resembled the ones found earlier at Shuwayhitiyah. Buried in a deposit more than two meters (seven feet) deep, the artifacts came to light during sand quarrying operations that cut into the site and dislodged them onto the wadi floor, where they were discovered and collected. Despite the small number of artifacts in the sample, the tools strongly resembled those in the Developed Oldowan tradition of Africa, which suggested that they had been made during a time frame similar to that of the Shuwayhitiyah artifacts.
Shuwayhitiyah and Najran were two exceptionally old sites in Saudi Arabia. About 160 kilometers (100 miles) north of Najran was a probable third site, located on the east bank of Wadi Tathlith. Its artifacts represented a very early stage of another industry called Acheulean, but without the usual array of hand axes, cleavers and picks characteristic of an Acheulean collection. Although its artifacts differed from the other two, the Tathlith site could be as old as Shuwayhitiyah or Najran, since Early Acheulean stone tools were apparently made at the same time as Developed Oldowan ones at many sites in East Africa.
These three sites in Saudi Arabia apparently date from an early part of a geological epoch known as the Pleistocene, which began more than two million years ago and ended within the past ten thousand years. It was a time when huge ice masses covered the northern parts of Europe and North America in episodes called glacials, only to melt away during warmer intervals referred to as interglacials. No one knows how many glacials and interglacials crosscut the Pleistocene; deep-sea cores suggest that there were at least 10. And while ice sheets did not cover Arabia, climate changes certainly affected the whole region (See Ammco World, March-April 1980). During glacial episodes, Arabia became cooler and drier. In warmer interglacials, the climate became milder and more humid, and therefore more attractive for human occupation. Climatic variation during the Pleistocene thus had a direct impact on the number and location of early sites.
The discovery of these very early sites in Saudi Arabia raised some perplexing questions: Who were the people who made these tools? Were they the first ones to migrate to Arabia? Where did they come from? When? And what route did they take?
To answer those questions we must turn to Africa, where the earliest humans, a species known as Homo habilis, first appeared a little more than two million years ago. These remote ancestors of ours, with brains only half the size of our own, lived mainly in eastern and southern Africa at such places as Olduvai Gorge in Tanzania, Lake Turkana in Kenya, the Omo and Awash Valleys of Ethiopia and the Transvaal of South Africa. A little more than a million and a half years ago, a larger and more advanced hominid called Homo erectus made its debut. This species, with greater physical and intellectual powers, was the first true explorer -more daring, more enterprising and more determined than its predecessors. It was Homo erectus who introduced new tool forms into the artifact inventory of the forerunner species, gradually replacing Developed Oldowan types with new Acheulean forms.
Equally important, it was Homo erectus who, after expanding into other parts of Africa, turned eastward and crossed over into Asia, marking the first time humans had left their continent of origin to set foot in a continent totally uninhabited. This initial migration into Asia by Homo erectus was an epochal event of surpassing importance, the forerunner of all future feats of exploration by man, which culminated in the peopling of the entire planet.
Two routes were available for Homo erectus to enter Asia. One entailed a long land journey down the Nile and across the Sinai into northern Arabia; the other involved a brief water crossing at the Bab al-Mandab, the narrow strait at the entrance to the Red Sea that separates Africa from southern Arabia. In either case, Arabia would have been the doorway to the entire Asian continent.
Since the second of these two routes was shorter and more direct than the land passage along the Nile, we feel that this was probably the direction taken by small bands of Homo erectus on their first migration into Asia about a million and a half years ago. Thus, the tool sites at Najran and Tathlith may be vestiges of those early migrations, as may the five recently discovered pre-Acheulean sites in the Hadhramaut mountains of southern Yemen.
On the other hand, if Homo erectus first entered Asia by way of northern Arabia, Shuwayhitiyah could represent a surviving remnant of that journey, as could the other early sites of Ubeidiya in Palestine and Sitt Markho and Khattab in Syria.
In either case, whether migration proceeded by way of the north or the south, it was necessary to cross Arabia first before continuing further. For that reason, the oldest sites in the world, next to those in Africa, should be found in Arabia, which occupied a pivotal position astride the path of early intercontinental migration in Lower Pleistocene times.
While Developed Oldowan sites more than a million years old are rare, Acheulean sites are more common - and with good reason. The Acheulean tradition lasted longer than any tool industry in human prehistory. It persisted almost a million and a half years, beginning while the Developed Oldowan tradition was still in place and ending only about 150,000 years ago. Its longevity accounts for its ubiquity.
In Arabia, some Acheulean sites were found by Aramco geologists between the 1930's and 1950's during petroleum surveys; others were identified by members of the US Geological Survey while mapping Saudi Arabia and defining its geology. The majority were discovered by small teams of archeologists, mostly Saudis and their American colleagues, during the five-year archeology survey program (1976-80) sponsored by the Directorate General of Antiquities and Museums of the Ministry of Education (See Aramco World, November-December 1990). Others surfaced in subsequent years during more intensive local surveys, excavations and stabilization projects.
To date, nearly 200 Acheulean sites of Middle Pleistocene age have been recorded in Saudi Arabia. They occur with highest frequency in the central, western and southwestern provinces, and are fewer in the east toward the Gulf coast. They consist of artifacts found on the descending surface of alluvial fans - delta-shaped deposits of material left by rivers of bygone times - or on terraces, exposed by wind or water erosion, overlooking a wadi, spring or Pleistocene lake (See Aramco World, May-June 1989). Where water was in plentiful supply, a dozen or more sites could appear, although not all were necessarily occupied at the same time. Usually, we believe, these sites were inhabited only temporarily, as transient stations to shelter residents for a few weeks.
It has become increasingly evident that climate changes in the Pleistocene triggered population fluctuations in Arabia. These population shifts corresponded to the prevalence of moist or arid conditions in the Peninsula. Nowhere is this more evident than in the Saffaqah Valley of central Arabia. The Saffaqah Valley is oriented in an east-west direction, about 27 kilometers (17 miles) southeast of the town of al-Dawadimi. Paralleling the south side of the valley is a long, narrow natural rock dike that continues for many kilometers, sometimes projecting above the surface some 25 to 50 meters (80 to 160 feet), at other times buried underground only to surface farther on. It was caused by the extrusion of molten andesite and rhyolite rock millions of years ago that punched up through a crack in the granite floor of the valley, creating both the series of elongated hills that form the dike and the long basin that adjoins it. Where they are exposed, the hills that make up the dike vary in length from 450 meters (1500 feet) to three kilometers (two miles), and are separated from one another by approximately a kilometer (2/3 mile).
During interglacials of the Pleistocene, the area experienced increased rainfall, which created a large lake in the middle of the valley. Emptying into the lake was the flow from two waterfalls that emerged from the dike. The presence of a freshwater lake, the influx of plant and animal life that such a body of water would attract, and the availability of andesite and rhyolite from the dike itself - good raw material for making stone tools - made the Saffaqah Valley a center for prehistoric occupation. It was not surprising, then, to find 26 Acheulean sites there in 1982-83, most of them dated at least a quarter of a million years old. Twenty-five of these sites were Middle Acheulean, one a later Upper Acheulean, and one other site represented an even later tradition called Mousterian. As climate deteriorated and the lake dried up, so did the population, until finally the valley was abandoned in Mousterian times, about 50,000 years ago.
Of the 25 Middle Acheulean sites near al-Dawadimi, one was excavated by archeologists. It extended down the slopes of the dike toward the former lake. Excavators dug a trench some three meters (10 feet) wide and 11 meters (35 feet) long to a depth of more than one and a half meters (five feet), until they reached bedrock. This excavation was significant for two reasons: First, it yielded firm uranium-thorium dates that placed the site more than 200,000 years before the present.
Uranium-series dating is a method used by archeologists based on the natural, unvarying radioactive decay of uranium and its daughter products, including thorium. Because we know just how rapidly uranium decays, and because uranium isotopes are soluble in water and those of the daughter elements are not, a specialized laboratory can take as little as 100 grams (3½ ounces) of calcium carbonate from rocks found at an archeological site and, by comparing the ratios of the different elements, date the rock with an accuracy of about seven percent, under ideal circumstances. The method is widely accepted, and is especially good for ages between 50,000 and 500,000 years ago, which lie beyond the range of reliable radiocarbon dating.
The second significant result of the al-Dawadimi excavation came from analysis of the artifacts found there. There were seven clusters of highly correlated tool types, indicating that the inhabitants of the site performed seven distinct functional activities, which took place on different parts of the site at different times. Three of these were animal-related - butchering, splitting bones, perhaps to obtain nourishing marrow, and scraping hides - and three involved tool production: woodworking, bone-working and stone-tool manufacture. The seventh activity dealt with plant gathering and processing.
The corrosive effects of alkali in the soil at al-Dawadimi would have destroyed all organic remains such as bone, wood, or antler that may have been present. Thus, no artifacts made of these materials appeared, but we could nonetheless infer their existence from the presence of certain stone implements - burins, notches and chisels - that were used to produce them. Al-Dawadimi was the first excavation of a Pleistocene site in Saudi Arabia; it yielded a remarkable total of 11,630 Middle Acheulean artifacts.
In this brief overview, we have focused almost exclusively on the oldest sites in Arabia, those that fit into the category defined as Lower Paleolithic, or Old Stone Age. Besides those very ancient localities, sites of later periods also exist in abundance - such as the Mousterian period of the Middle Paleolithic; Upper Paleolithic and Neolithic remains; and sites dating from Greek, Roman and Islamic times. But it is in pursuit of the oldest sites that we concentrate our efforts, because we feel that Arabia stands on the threshold of a golden age of archeological research and discovery, with a vast potential in the form of sites connected with early humans, waiting to be discovered in the foothills, escarpments, wadis and deserts of the kingdom.
As archeological surveys and excavations continue and expand, Arabia, humankind's doorway to the world, may well emerge as the Olduvai Gorge of the 21st century.
Dr. Norman M. Whalen is a professor of anthropology at Southwest Texas State University. David W. Pease is a doctoral candidate in anthropology at Southern Methodist University in Dallas. Under the auspices of Saudi Arabia's Ministry of Education, they have worked together on four archeological expeditions in the kingdom, and a fifth in Yemen.