A haul of picks, flakes and hand axes, recovered from ancient sediments in Kenya, has been reported to be 1.76 million years old. This is as per a new geological study being reported in the journal Nature.

The implements were unearthed by archaeologists when excavating mudstone banks on the shores of Lake Turkana in the remote north-west of the country.

No erectus fossils was found with the Turkana tools. However, a skull of that species was excavated last year in the same sediment level across the lake. This suggests that Homo erectus was responsible for these particular tools, which were made with what scientists refer to as Acheulean technology. The term indicates the type of oval and pear-shaped hand axes and other implements that were a specialty of early humans.

A characteristic of the Homo erectus, a predecessor of modern humans, was his stone tools. It is an advanced technology displaying a good deal of planning and skillfulness. To date, though, scientists have not been able to point a specific date on the earliest known evidence of his stone tool-making.

“I was taken aback when I realized that the geological data indicated it was the oldest Acheulean site in the world,” said the lead author of the report, Christopher J. Lepre, a researcher at Lamont-Doherty.

Lepre's findings indicate that multiple hominin groups with differing tool-making abilities could have dispersed to Eurasia, and that H. erectus either didn't go first, or didn't take Acheulian tools with them.

From a stone-tool perspective, all the evidence points to the idea that Oldowan hominins were the first to leave Africa, said Lepre.

However, which species is responsible for the spread of Oldowan tools is still open for speculation.