Scarcer food may have pushed early humans to rework stone tools for longer use

Approximately 300,000 years ago, early Homo sapiens emerged in Africa, ushering in a new era of cultural and technological advancements, now known as the Middle Stone Age. To gain insight into the lives of the earliest humans, researchers have turned to the environments they inhabited. A study led by scientists from the CNRS and University of Kiel in Germany examined sediment samples from Florisbad and Lombard's Drift sites in central South Africa.

Around 200,000 years ago, the landscape of central South Africa was vastly different from today, with a mix of shrubs, temperate plants, and abundant fresh water, creating non-analogous ecosystems that have no modern equivalents. This contrasted sharply with the arid grasslands that dominate the region now. The climate was also more stable, with rainfall distributed evenly throughout the year, unlike the seasonal pattern seen today.

These ancient landscapes may have influenced the availability of food resources and, consequently, the practices of early Homo sapiens. Scientists analyzed n-alkanes, molecules found in plant leaf waxes, and preserved in sedimentary beds, to gain insight into past vegetation and climate conditions. By using luminescence dating on sand grains, they determined that certain sedimentary layers at Florisbad dated back to around 200,000 years ago, where the oldest Homo sapiens skull was discovered in 1932.

Comparing the reconstructed ancient landscapes with the stone tools and faunal remains found at the Florisbad site, researchers found a correlation between environmental productivity and flaking techniques. During periods of food scarcity or increased difficulty, tools were more heavily retouched, extending their durability and allowing for reuse and optimal use of manufacturing time. Conversely, when resources were more abundant, tools required less retouching and could be produced more quickly for cutting meat.

These findings suggest that early humans were constantly adapting their subsistence strategies, such as material management and animal carcass processing, to the challenges posed by their ever-changing ecosystems. The researchers believe that this approach could be applied to other sites in southern Africa, providing a deeper understanding of how climatic variability and ecosystem changes shaped the history of early human populations.