Climate Change Sparked Stone Age Technological Innovation in Modern Humans

Could climate change have sparked Stone Age cultural innovation in modern humans? That's what a new study is claiming. Scientists have used new evidence to show that technological and cultural improvements took place abruptly during a time when temperatures and climate were changing.

Modern humans originated from Africa during the Stone Age, between 30,000 and 280,000 years ago. At the time, the beginnings of symbolic expression were beginning to emerge along with tool making. Humans were even beginning to craft jewelry and construct the first agricultural settlements.

Yet all of this innovation in sub-Saharan Africa may have been sparked by climate change. Over the last million years, the global climate has varied between glacial periods and interglacial periods. Masses of ice have covered continents in the northern hemisphere before receding during warmer periods. Changes in this cycle occur approximately once every 100,000 years.

Yet within this larger cycle, there have been abrupt climate changes, sometimes happening in the space of only a few decades. These sudden shifts can sometimes have variations of up to 10 degrees Celsius in the average temperatures in polar regions caused by changes in the Atlantic circulation. These changes, in turn, can affect rainfall in southern Africa--the region where modern humans were once based.

In order to examine how climate might have affected our ancient ancestors, scientists analyzed river delta deposits at the edge of Africa, where every millimeter of sediment core corresponds to about 25 years of sedimentation. The ratio of iron to potassium in each layer actually allowed the researchers to estimate the amount of rainfall that occurred during a period of 100,000 years.

So what did they find? A series of rainfall spikes occurred between 40,000 and 80,000 years ago. The amount of rainfall rose sharply over just a few decades before falling again soon afterward. With this evidence along with archaeological findings, the scientists were able to tell that these climate changes coincided with increases in population, activity and production of technology. In fact, the end of certain stone tool industries of the period coincides with the onset of a new, drier climate.

The findings reveal a little bit more about the cultural and technological evolution of our ancestors. In addition, it reveals the importance of climate change and how the weather played a crucial role in the origins of our modern behavior.

The study forms part of the GATEWAYS project of the European Commission's 7^th Framework Program.