By BBC News Online's Helen Briggs

Stone tools dated to 1.36 million years ago provide the earliest evidence yet of human occupation of northeast Asia.

The tools, which were found at an ancient settlement in northern China, show that early humans were able to adapt to extremes of temperature relatively early in their history.

The crude implements were likely to have been made by early humans known as Homo erectus, a predecessor to our own species, Homo sapiens.

According to many scientists, Homo erectus was the first early human to move out of Africa to populate Asia and Europe.

The tools were found as far as 40 degrees north - at Xiaochangliang in the Nihewan Basin, north China.

This comes as a surprise because the area was thought to be inhospitable to early humans of the time, which were used to warmer climes. It suggests that early humans emerged from the tropics with an inbuilt ability to adapt to their environment.