The analysis of artifacts from a 325,000-year-old site in Armenia shows that human technological innovation occurred intermittently throughout the Old World, rather than spreading from a single point of origin, as previously thought.

The study, published in the journal Science, examines thousands of stone artifacts retrieved from Nor Geghi 1, a unique site preserved between two lava flows dated to 200,000-400,000 years ago. Layers of floodplain sediments and an ancient soil found between these lava flows contain the archaeological material.

The dating of volcanic ash found within the sediments and detailed study of the sediments themselves allowed researchers to correlate the stone tools with a period between 325,000 and 335,000 years ago when the Earth's climate was similar to today's.

The stone tools provide early evidence for the simultaneous use of two distinct technologies: biface technology, commonly associated with hand axe production during the Lower Paleolithic, and Levallois technology, a stone tool production method typically attributed to the Middle Stone Age in Africa and the Middle Paleolithic in Eurasia.

Traditionally, Archaeologists use the development of Levallois technology and the disappearance of biface technology to mark the transition from the Lower to the Middle Paleolithic roughly 300,000 years ago.

Archaeologists have argued that Levallois technology was invented in Africa and spread to Eurasia with expanding human populations, replacing local biface technologies in the process. This theory draws a link between populations and technologies and thus equates technological change with demographic change.

The co-existence of the two technologies at Nor Geghi 1 provides the first clear evidence that local populations developed Levallois technology out of existing biface technology.

"The combination of these different technologies in one place suggests to us that, about 325,000 years ago, people at the site were innovative," says Daniel Adler, associate professor of Anthropology at the University of Connecticut, and the study's lead author.

Moreover, the chemical analysis of several hundred obsidian artifacts shows that humans at the site utilized obsidian outcrops from as far away as 120 kilometers (approximately 75 miles), suggesting they must also have been capable of exploiting large, environmentally diverse territories.

The paper argues that biface and Levallois technology, while distinct in many regards, share a common pedigree. In biface technology, a mass of stone is shaped through the removal of flakes from two surfaces in order to produce a tool such as a hand axe.

The flakes detached during the manufacture of a biface are treated as waste. In Levallois technology, a mass of stone is shaped through the removal of flakes in order to produce a convex surface from which flakes of predetermined size and shape are detached.

The predetermined flakes produced through Levallois technology are the desired products. Archaeologists suggest that Levallois t echnology is optimal in terms of raw material use and that the predetermined flakes are relatively small and easy to carry. These were important issues for the highly mobile hunter-gatherers of the time.

It is the novel combination of the shaping and flaking systems that distinguishes Levallois from other technologies, and highlights its evolutionary relationship to biface technology.

Based on comparisons of archaeological data from sites in Africa, the Middle East, and Europe, the study also demonstrates that this evolution was gradual and intermittent, and that it occurred independently within different human populations who shared a common technological ancestry, says Adler. In other words Levallois technology evolved out of pre-existing biface technology in different places at different times.

This conclusion challenges the view held by some Archaeologists that technological change resulted from population change during this period. "If I were to take all the artifacts from the site and show them to an archaeologist, they would immediately begin to categorize them into chronologically distinct groups," Adler said.

In reality, the artifacts found at Nor Geghi 1 reflect the technological flexibility and variability of a single population during a period of profound human behavioral and biological change. These results highlight the antiquity of the human capacity for innovation.