Intelligent Homo erectus "Used Shells for Tool Production and Engraving"

I've commented in the past on the debate over whether Homo erectus was an unintelligent, bungling prehuman hominid, or an intelligent boat-building seafarer. Now a new paper in Nature, "Homo erectus at Trinil on Java used shells for tool production and engraving," weighs in on the question. According to the abstract:

The manufacture of geometric engravings is generally interpreted as indicative of modern cognition and behaviour. Key questions in the debate on the origin of such behaviour are...