A mammoth skeleton at the State Museum for Natural History in Stuttgart, GermanyDANIEL NAUPOLD/dpa/AlamyArchaeologists excavating 400,000-year-old rock in western Ukraine have uncovered fragments of what could be the oldest human-made ivory objects ever found. These artefacts would have been too soft to use as cutting tools, but they could have been used as teaching aids, the researchers suggest.If the interpretations are correct, they add to an apparently increasing appreciation of the intelligence of pre-modern humans, says Gary Haynes at the University of Nevada.