Our early human ancestors were a clever lot. They quarried limestone for tools, worked collectively to make them but then curiously threw them away within a short distance of the work-site.
A talk yesterday at the British Association meeting at the University of Leicester explored the mindset and social skills of an early hominid, Homo erectus. Dr Mike Petraglia of the University of Cambridge described excavations at an ancient limestone quarry in Karnataka, India. The Isampur quarry was discovered in 1993 buried under several metres of sediment. These human ancestors used the quarry to make stone axes and cleavers and so far 15,000 artefacts had been recovered, Dr Petraglia said.
The earliest stone tools date from 1.2 million years ago and the Karnataka artefacts appear to be between 600,000 and 400,000 years old, he said. His team studied the tools and how they were made as a way to understand the creatures that made them, giving insights into "the mind of early humans", Dr Petraglia said.
"By looking at those tools we can get at their particular actions, their thought processes as they processed that stone."
The Isampur stone-cutters were very different from either apes or modern humans. "These were creatures that have no analogues today."
They had a brain about half the size of a modern humans but the clues they left behind show they "were anticipating their needs", he said.
The hominids collected tough basalt-containing "hammer stones" one to two kilometres away and then brought them to the quarry.
"We know they were anticipating their needs. They were planning," he said.
The hammer stones were used to chip away at the limestone pieces to create a flaked bifacial tool. Surprisingly, after all the effort, the tool-makers often discarded their axes and cleavers within five kilometres of the quarry. "They were not curating their tool kits," Dr Patraglia said. "There is a very high discard rate, there is a lack of long-range planning going on."
He believes that there was some level of co-operation between the workers. "We have actually replicated how the tool-makers did it. I do think there is a lot of social co-operation involved in it. It sometimes takes two people to flip slabs [of limestone] and hold them in place."
This suggested that they might have been using a "proto-language" to communicate.