The Nefud Desert is an oval depression in the northern Arabian Peninsula, known for its red sand, sudden violent winds, and large crescent-shaped dunes. It is 290 kilometres long, 225 kilometres wide, and sees rain only once or twice a year. But in antiquity, there were lakes.
     Dr Eleanor Scerri of the University of Bordeaux and her colleagues call them 'palaeo-lakes'. Today these ancient lakes are only sediments and other features that tell us that there was once water, but scientists have also found fossil flora, fauna, and archaeological features and artefacts.
     Scerri and her colleagues detail their discovery of 13 sites associated with palaeo-lake basins dated to Lower and Middle Palaeolithic times - from 2.5 million all the way to 30,000 years ago. "One of the sites, T'is al Ghadah, may feature the earliest Middle Palaeolithic assemblage of Arabia," they write.
     According to Scerri and her colleagues, ancient humans came and went in this region, following the rivers and settling around the lakes during wet periods, bringing stone tool cultures that differed depending upon their culture, and perhaps origin. Who were they? Thus far, no human fossils have been found at any of the sites.
     Despite the diversity, the researchers suggest that there was at least one common characteristic among these various ancient groups - a rarity of formal tools, but strong similarities in production techniques. How they produced their tools could give clues to their relationship and origins.
     The survey is one of a number of efforts to research human dispersal and habitation from northeastern Africa through Arabia and beyond. For Scerri, early modern humans may have arrived at various times from northeastern Africa, traversing what is called the 'Saharo-Arabian belt' via land routes - perhaps more than 100,000 years ago.
     It is a theory based on years of research, that may help to explain the presence of early modern humans in Southwest Asia in prehistory. Considered controversial by some scholars, it contrasts with one widely-held theory that early modern humans dispersed rapidly out of Africa primarily along the coasts about 55,000 years ago. The evidence for this shows up in small blade technologies - very similar to stone tools made in what is called the 'Howiesons Poort' industries of southern Africa - and symbolic items such as beads, incised and decorated items and bone tools.
     Scerri and others suggest a different scenario. "Human movements across Southern Asia would have been slow, continental advances during humid periods, and contractions (and even extinctions) during arid periods. Mapping of environments from Arabia to Southeast Asia indicate dramatic variability in habitats." Major revisions in genetic studies "suggest that 'Out of Africa' movements may date to 120,000 years ago, which would correspond with fossils of Homo sapiens in the Levant, and Middle Palaeolithic technologies in southern Asia."
     Evidence thus far suggests an ancient human presence in the Nefud that may bear significantly on the study of prehistoric human dispersal.

Edited from Popular Archaeology (20 October 2014)