Archaeologists are excited about the discovery of several artefacts in Papua New Guinea made from volcanic black glass, which could be up to 6,000 years old.
Dr Robin Torrence, senior principal research scientist at the Australian Museum, says workmen found the penis-shaped objects while using a bull dozer and recognised their significance.
She has told Radio Australia's Pacific Beat the objects - known as obsidian - were probably ceremonial.
"They're very big, they're 20 centimetres long, they're very flat and they're sharp, but the edges - if you look under a microscope - you can see they've never been used," she said.
"The thing is that they're so thin and flat and sharp, that if you tried to use them for anything they'd break. So right away, you know you're not dealing with a kind of functional utilitarian tool.
"It is much more likely that something so big and flashy was there to catch attention, and the clearly manufactured shape is sending some messages out to people," she said.
The tools date back to before the Lapita people, and could shed new light on the history and origins of the Pacific region's ancient civilisations.
Dr Torrence says the artefacts will be housed at the National Museum of Papua New Guinea.