Ancient human relatives crafted sharp-edged tools out of animal bones around 1.5 million years ago, researchers say.Discoveries at Tanzanias Olduvai Gorge, a famous East African fossil location, represent the oldest known evidence of systematic bone tool production by hominids, according to archaeologist Ignacio de la Torre of CSIC-Spanish National Research Council in Madrid and colleagues.Excavations conducted from 2015 through 2022 unearthed 27 bone tools in sediment that had already been dated, the scientists report March 5 in Nature. Either of two fossil hominids known to have lived at Olduvai Gorge around 1.5 million years ago a possible direct human ancestor called Homo erectus or a side-branch species dubbed Paranthropus boisei could have created the bone artifacts, they say.While stone toolmaking emerged as early as 3.3 million years ago, bone tools generally date to no earlier than around 500,000 years ago. Much older origins of bone toolmaking were suggested by the identification of a 1.4-million-year-old hippos leg bone fashioned into a cutting or sawing tool, which had gone unexamined since its discovery at an Ethiopian site in 1994.An ancient bone tool kit unearthed in Tanzania exhibits a range of sizes and modifications.CSICEven older artifacts recovered at Olduvai Gorge come from a bone tool kit, the scientists say. Implements of varying sizes and shapes were identified as pieces of leg bones, mostly from elephants and hippos. Pounding marks appear where hominids sharpened the edges of bones. The largest tools, made from elephant bones, reached up to 38 centimeters long. Thats roughly the distance, on average, from an adults elbow to fingertips.Six bone tools featured a carved notch on one end, which perhaps served as a grip, and a sharp point at the other end. Several other bone tools resemble pear-shaped stone hand axes.Archaeologists consider stone hand axes the main innovation of the Acheulean industry, a tool tradition that emerged roughly 1.7 million years ago. We believe that the Olduvai bone tools represent a technological transfer [by hominids] from stone to bone, de la Torre says.His group excavated many hippo bones bearing butchery marks, suggesting that Olduvai hominids exploited hippo carcasses for food as well as bones suited for toolmaking. But few elephant remains turned up. Elephant-bone tools were brought to the site from elsewhere, the investigators suspect.