Evolution in times of climate change

The origins of some of our fundamental traits could lie in climate change

By Kaushik Das Gupta
Published: Friday 24 May 2013


Climate in South Africa abruptly turned warm and wet around 100,000 years ago. The humid weather lasted several hundred years. Such humid spells would return to South Africa several times in the next 60,000,  fostering cultural changes and technological innovation that bear rudiments of modern behaviour, according to a new study.

The origins of some of the ways we communicate, relate to other human beings as well as to nature lie in changes in climate, according to the study published in the journal Nature Communications.  Lead researcher, Martin Ziegler, an earth science researcher at Cardiff University in Wales, told NBC News, “the study is the first to link climate change in ancient times with cultural and technological innovations.”

Ziegler and his colleagues analysed marine sediments off the coast of South Africa to show that “South Africa experienced spells of warm climates, when the Northern Hemisphere  reeled under extremely wet conditions.” In such times it acted as a “refugia for people from Sub-Saharan Africa,” says Ziegler.

Ian Hall, professor at Cardiff University's School of Earth and Ocean Sciences and one of the co-authors of the paper, says, “When the timing of these warm and wet pulses was compared with the archaeological datasets, we found remarkable coincidences. The occurrence of several major Middle Stone Age industries co-incided with the onset of periods with increased rainfall.” The humid conditions coincide with significant periods of human advancement made about 71,500 years ago, and again between 64,000 and 59,000 years ago.  During these times human beings made significant advances in the production and use of stone tools and in the use of symbols, thought to be essential for the development of complex language. These periods have been linked with the first appearance of jewellery.

The Nature Communications paper could solve one of the mysteries of human evolution. Archaeological data suggests that early human advances in technology moved in fits and starts. Scientists and historians are sometimes clueless when confronted with advances in stone technology in Sub-Saharan Africa around 90,000 years ago and their near disappearance a few thousand years later. “Scientists have offered many suggestions as to why these cultural explosions occurred where and when they did, including new mutations leading to better brains, advances in language, and expansions into new environments that required new technologies to survive. The problem is that none of these explanations can fully account for the appearance of modern human behavior at different times in different places, or its temporary disappearance in sub-Saharan Africa," according Stephen Shennan who heads UCL's department of archaeology.

"There is a very good fit between rapid climate change and the occurrence and disappearance of these first evidences of modern behavior in early humans," believes Ziegler. It's well possible that people from Sub-Saharan Africa migrated to South Africa, bringing their advanced tool-making technology.

Chris Stringer, an authority on human origins at London's Natural History Museum and one of the co-authors of the study, suggests that as population density increased in South Africa, people networked, shared ideas and innovations.The new findings, he told NBC, fit well with the idea that population density breeds cultural innovation.

"Those dense populations form networks over the landscape which are no longer huge patches of arid land that they cannot cross," he said. Tool-making technology is not the only indicator of cultural efflorscence.  Messages written in ochre, a type of pigment, indicate an advancement in communications, according to Stringer. Remains of seashell jewellery that are dated to the times of wet weather are perhaps an indicator of social rank, according to historians.


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