In 2007, an analysis of cut marks on two bovid bones found in Sangiran, showed them to have been made 1.5 to 1.6 million years ago by clamshell tools. This is the oldest evidence for the presence of early humans in Indonesia. Fossilised remains of "Homo erectus" in Indonesia, popularly known as the "Java Man" were first discovered by the Dutch anatomist Eugène Dubois at Trinil in 1891, and are at least 700,000 years old. Other "H. erectus" fossils of a similar age were found at Sangiran in the 1930s by the anthropologist Gustav Heinrich Ralph von Koenigswald, who in the same time period also uncovered fossils at Ngandong alongside more advanced tools, re-dated in 2011 to between 550,000 and 143,000 years old. In 1977 another "H. erectus" skull was discovered at Sambungmacan. The earliest evidence of artistic activity ever found, in the form of diagonal etchings made with the use of a shark's tooth, was detected in 2014 on a 500,000-year-old fossil of a clam found in Java in the 1890s, associated with "H. erectus".