Found at the Konso-Gardula site in Ethiopia:
Homo erectus, a possible direct ancestor of people today, crafted a surprisingly cutting-edge tool out of a hippo’s leg bone around 1.4 million years ago, researchers say…
Along with a variety of stone tools now recognized at several East African sites (SN: 3/4/20), the bone hand ax “suggests that Homo erectus technology was more sophisticated and versatile than we had thought,” Suwa says.
Bruce Bower, “This 1.4-million-year-old hand ax adds to Homo erectus’ known toolkit” at ScienceNews
For some reason, they keep evolving to be smarter when we do more research.