Providing the x-axis
Central Asia is widely accepted as a key route for human expansion into Asia and plenty of lithics can be found in the hills of the Khovaling region, showing that the migratory paths of the first humans to leave Africa went through here.
There has long been an interest in establishing when humans arrived: Fifty odd years ago Soviet archaeologists excavated huge amounts of lithics. However, the science wasn’t available to put an exact age on the artefacts and thus establish when people occupied those landscapes. “They could only guess by counting layers of soil,” Jan-Pieter Buylaert explains.
While this method, called pedostratigraphy, can reveal relative ages of the soil layers, only absolute dating techniques can establish exact dates, he says: “Broadly speaking, pedostratigraphy works, but you can make huge errors of up to hundreds of thousands of years. That’s where we come in as luminescence specialists to date the top 250,000 years of the accumulated dust layers.”
Luminescence is a method that can determine when material like sand was last exposed to sunlight (see box below for explanation). So, by analyzing loess samples collected in lightproof tubes at regular intervals down through the excavation trenches, the DTU-specialists can help accurately date the loess layers that make up the hills they are studying. Knowing the age of the soil where lithics are found is important in establishing when they were left there—presumably as inhabitants moved on.