OHIO, United States - Metin Eren wasn't satisfied just digging up ancient arrowheads to learn about the past. He wanted to use them for their intended purpose.

But shooting and shattering priceless millennia-old tips is out of the question, so instead, the archaeologist chips replicas of the stone-age weapons by hand.

"We can break 'em and throw 'em," he says. "Our imagination is the limit."

The 34-year-old professor at Kent State University, in Ohio in the United States, specializes in experimental archaeology recreating ancient pots, knives and arrows. By testing the replicas in ways impossible with the originals, archaeologists study how tools found in archaeological digs were actually used.

"The stuff that we find, it's just stuff," says Brian Andrews, an archaeologist at Rogers State University. "Stuff's cool, but we're not interested in stuff for the sake of itself. We're interested in the human behaviors that went into making it."

Eren's experiments focus on making sense of ancient weapons littered across the Americas, illustrating how humans first settled the Western Hemisphere: through careful preparation, long-term planning, and refined technology.

"Even though it's the Stone Age, they're still thinking in a very modern way," Eren says.

Already he has cracked one longtime mystery. In the early 1900s, archaeologists found unusually shaped arrowheads in North America, with grooves carved from the base halfway to the head's tip. They first appeared over 13,000 years ago and spread rapidly across the continent, but existed nowhere else. Researchers were puzzled why the grooves were carved, with speculation running from religious rituals to mere decoration.

That's where experimental archaeology came in. By testing the pressure at which the arrowheads would crack using a crusher and computer models, Eren discovered the grooves act as a shock absorber. It allows the arrowhead's thinned base to crumple slightly and absorb energy upon the arrow's impact, making the head less likely to break.

Archaeologists call it the "first truly American invention".

On a Thursday morning, Eren gingerly examined a sliver of obsidian. Such blades are "sharp to the molecule," he said, and one nearly sliced off his left pinkie in graduate school.

In his hand, he's holding a piece of the puzzle of how humans came to rule the world. By refining their weapons, ancient Americans learned how to adapt to all sorts of conditions.

"They knew they were going into unknown territory, and because of that they actually prepared extremely well technologically," Eren said. "Understanding this process of colonization is important to understanding how we are today."

Associated Press