Tens of thousands of years ago people living at the southern tip of Africa were more connected to those hundreds of kilometers away than has previously been recognized, archaeologists have concluded. The findings are based on changes in stone tool design at two distant locations. How new designs spread remains unknown, but the work indicates the extent of cultural exchange among our ancestors.

Today, the 300-kilometer (180 miles) journey from Klipdrift Shelter to Dieplkloof Rockshelter, both in South Africa, can be done in an afternoon. In the Middle Stone Age, which lasted from 350,000 to 24,000 years ago, few people traveled such a distance in their lifetime. Yet it seems that ideas spread quickly from one site to another, with tool designs at the two locations mirroring each other during a period from 66,000 to 59,000 years ago.

The discovery was made when an international team of researchers examined thousands of stone tools found at the Klipdrift Shelter, located near the southernmost tip of Africa, but warmed by the Indian Ocean current. "The site of Klipdfrift Shelter is one of the few containing a long archaeological sequence that provides data on cultural changes over time during the Howiesons Poort," said the University of Geneva's Dr Katja Douze in a statement. "This makes it perfect to study the change in culture over time."

Douze and co-authors describe these changes in PLOS ONE. In particular, there was a shift from heat-treated silcrete to quartz and quartzite as the basis for blades. Tool changes often reflect changing environmental conditions, but in this case the authors think there was a cultural shift, with no obvious alteration in prey at the time.

The authors were struck, however, by the similarity of the changes to those seen over the same period at Diepkloof Shelter, north of what is now Cape Town. Diepkloof is further north, but chilled by a current from the Antarctic into an entirely different climatic zone and ecology.

The findings are somewhat surprising, because a specific style of tools, named for the technological period they come from, the Howiesons Poort, and featuring small blades and backed tools, first appears in the archaeological records at Diepkloof Shelter around 100,000 years ago. Howiesons Poort was only found at other sites in Southern Africa around 66,000 years ago, suggesting immensely slow cultural diffusion.

The paper also concludes the Howiesons Poort did not end at Klipdrift with some sudden abandonment of technology that had served its makers well for so long. Instead, this style of tool-making faded out gradually, a pattern similar to what has been found at three other rich South African archaeological sites. This bolsters the argument the shift was driven by changing preferences, rather than population collapse or an influx from elsewhere.