A rare haul of picks, flakes and hand axes recovered from ancient sediments in Kenya are the oldest remains of advanced stone tools yet discovered.
Archaeologists unearthed the implements while excavating mudstone banks on the shores of Lake Turkana in the remote north-west of the country.
The largest of the tools are around 20 cm long and have been chipped into shape on two sides, a hallmark of more sophisticated stone tool making techniques probably developed by Homo erectus, a long-dead ancestor of modern humans.
The stone tools, made for crushing, cutting and scraping, gave early humans a means to butcher animal carcasses, strip them of meat and crack open their bones to expose the nutritious marrow. Researchers dated the sediments where the tools were found to 1.76 million years old. Until now, the earliest stone tools of this kind were estimated to be 1.4m years old and came from a haul in Konso, Ethiopia. Others found in India are dated more vaguely, between 1m and 1.5m years old.
Older, cruder stone tools have been found. The most ancient evidence of toolmaking by early humans and their relatives dates to 2.6 million years ago and includes simple pebble-choppers for hacking and crushing. But the latest collection of stone tools from Kenya belong to a second, more advanced generation of toolmaking. Known as Acheulian tools, they are larger, heavier and have sharp cutting edges that are chipped from opposite sides into the familiar teardrop shape.
Most Acheulian stone tools have been recovered from sites alongside fossilised bones of Homo erectus. Writing in the journal Nature, a team of researchers led by Kent’s colleague Christopher Lepre describe finding the stone tools in a region called Kokiselei in the Rift Valley. The site is close to where several spectacular human fossils have been found, including Turkana Boy, an early human teenager who lived 1.5 million years ago.