Tools you can trust

Scientists have definitively dated the oldest stone tools discovered in east Asia. In the process, they have identified the most northerly known human occupation in China when Homo erectus walked the land.

The discovery shows that humans were well able to deal with a varying climate, adapting to high temperatures during the summer and extreme cold during the winter, according to the research by experts from the Chinese Academy of Sciences, California Polytechnic State University and the Smithsonian Institution in Washington, DC.

Details of their research are published today in the journal, Nature.

The tools in question, made of fine and course-grained chert and volcanic rock, were recovered in northern China 20 years ago. They had been claimed as proof of the earliest occupation of Homo erectus in eastern Asia but doubt remained about their true age.

Not any longer. Advances in a range of dating technologies, including "magnetostratigraphic analysis", which looks at the north-south magnetisation of rocks, has meant the stone tools can be dated quite accurately.

The stone layer from which they were recovered in Ziaochangliang, between the north China basin and the Mongolian Plateau, has now been dated to 1.36 million years old.

"This result represents the age of the oldest known stone assemblage comprising recognisable types of Palaeolithic tool in east Asia, and the earliest definite occupation in this region as far north as 40 degrees N," the authors report.

The timing of the earliest habitation and oldest stone technologies in different regions is a "contentious topic" in the study of human evolution, the authors note. A lack of accurately dated material was a particular problem for east Asia.

Being able to identify date and location of evidence of early humans is important both in evolutionary terms but also in terms of their migration as hominids pushed into new territories. This finding "provides a new perspective regarding early human populations in east Asia", the authors suggest. "It also denotes the oldest unambiguous presence of early humans in east Asia at a latitude of at least 40 degrees N."

This indicates something about the adaptability of Homo erectus who would have had to contend with the wide variations of temperature experienced in north China.

"The spread of toolmakers to this latitude implies that early Pleistocene human populations in east Asia were able to adapt to diverse climatic settings. It also suggests that populations might have dispersed to and from east Asia over a broad latitudinal range."

While early humans would have been well adapted to cope with the higher temperatures in the African regions from which they sprang, life so far north would have presented challenges. Homo erectus would have had to employ a range of technologies to survive in the cold.

The close analysis of the northern China rock strata also showed there were periods of severe aridification around the time that Homo erectus arrived there. A lack of water would have added to the a challenge for these early humans in their struggle to survive.