The Acheulian stone tool culture is an archaeological industry of stone tool manufacture. These tools are characterized by distinctive oval and pear-shaped “hand-axes” that were associated with Homo erectus and other pre Homo sapien species. It was the longest lasting toolmaking industry that appeared in eastern Africa over 1.75 million years ago, and 1.2 million years ago in India and continued till 130,000 years ago. By the time they were abandoned, Homo sapiens and other homonin species such as Neanderthals had expanded into Europe and western & central Asia, Denisovans had moved into north & eastern Asia, and late Homo erectus populations, the small-bodied Homo floresiensis and Homo luzonensis had occupied South East Asia.
A key site was discovered in the Thar Desert, Rajasthan, India. This site appears to be from about 177,000 years ago, shortly before Homo sapiens spread out across Asia. The sight was first excavated in the 1980s and now scientists have re-visited the area to examine it again.
In a new paper, the scientists reveal that the site of Singi Talav, on a lakeside in the Thar Desert, had a relatively recent population 177,000 years ago, making it the youngest Acheulian site. In earlier excavations it was thought to be the oldest site in India. The new study shows that Acheulean populations persisted in the Thar Desert, even after they had disappeared in eastern Africa around 214,000 years ago and Arabia 190,000 years ago. Stone handaxes and cleavers, typical of the Acheulean culture, form the largest amongst the stone tools collections found.
The researchers used modern techniques such as luminescence methods to date the sediment layers occupied by ancient human populations. This method relies on the ability of minerals like quartz to store and release radiation, making it possible to detect when they were last exposed to light. They also studied plant microfossils and soils to understand the ecology and environmental conditions of the site at the time the tools were made. Presence of rich grasses indicate periods of enhanced summer monsoons.
H. sapiens must have arrived to observe these ecological and environmental conditions at the western edge of the South Asian monsoon. While we have known that Homo sapiens expanded across Asia, fossils have been rarely discovered. Stone tools such as those found at Singi Talav can indicate how the different populations met and interacted. According to the study, “The Thar Desert marks a major adaptive boundary between monsoonal Asia to the east and the Saharo-Arabian desert belt to the west, making it a key threshold to examine patterns of hominin ecological adaptation and its impacts on patterns of behaviour, demography and dispersal.”
The scientists say, “This presents the first direct palaeoecological evidence for landscapes occupied by South Asian Acheulean-producing populations, most notably in the main occupation horizon dating to 177,000 years ago. Our results illustrate the potential role of the Thar Desert as an ecological, and demographic, frontier to Palaeolithic populations.”