What were the first words uttered by the early ancestors of modern humans?  According to a new study, one of the first possible sentences could have been, "Tool bad," and likely occurred between 2.5 and 1.8 million years ago.

The study, published in the journal Nature Communications, provides compelling evidence that stone tool-making helped push the evolution of language and teaching among prehistoric human ancestors in the African savanna.

"We suggest that the use of tools drove the evolution of language, and it seems likely that 'words' for things other than current emotional states would have been very useful for learning to knap," lead authof of the study and researcher from the University of California, Berkeley, Thomas Morgan says. "The use of sounds or gestures for non-emotional concepts such as 'yes,' 'no,' 'here,' 'there,' 'good' and 'bad' would likely have been really useful."

Morgan, University of Liverpool archaeologist Natalie Uomini and their team together conducted a series of experiments in teaching contemporary humans the art of "Oldowan stone knapping." Oldowan refers to the oldest known stone cutting tools, which were likely made by Homo habilis (aka "The Handy Man") and possibly also Homo rudolfensis, Australopithecus garhi and Paranthropus boisei.

The earliest known Oldowan tools date back to 2.5 million years ago and consist of butchering "flakes" created by hammering a hard rock against certain volcanic or glassy rocks such as basalt or flint.  The tools remained basically the same until 1.8 million years ago, when more sophisticated Acheulean hand-axes and cleavers marked the next generation of stone tool technology.

Researchers tested five different ways to convey Oldowan stone-knapping skills to more than 180 collect students and discovered that the demonstration using spoken communication, versus imitation, non-verbal presentation or gestures, yielded the highest volume and quality of flakes in the shortest amount of time with the least amount of waste. The researchers suspect that other tasks, such as hunting and gathering, also could have contributed to the development of language and other teaching skills, but probably not to the same degree as tool making.

Language has more than likely been around for at least 2 million years, casting very little doubt that many human-like species, such as Neanderthals, did a lot of talking.

"Language was certainly already present before the Neanderthals and our ancestors split," Uomini says. "The Neanderthals had some of the most complex stone tools ever made, which are also the most difficult for modern day knappers to replicate. That's why we think that their communication and teaching system must have been sophisticated enough to transmit the subtle and long 'recipes' for making their tools."