Landscapers were digging a hole for a fish pond in the front yard of a Boulder home last May when they heard a "chink" that just didn't sound right.

They had stumbled on a cache of more than 83 ancient tools buried about 13,000 years ago by the Clovis people — ice age hunter-gatherers who remain a puzzle to anthropologists.

But the landscapers dug up one important piece of the puzzle.

Biochemical analysis of protein residue revealed the tools were used to butcher camels, horses, sheep and bears, proving that the Clovis people ate more than just woolly mammoth meat for dinner.

"A window opens up into this incredibly remote way of life that we normally can't see much of," said University of Colorado-Boulder anthropologist Douglas Bamforth, who is leading the CU study of the find.

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The tools reveal an unexpected level of sophistication, Bamforth said, describing the design as "unnecessarily complicated," artistic and utilitarian at the same time.

Patrick Mahaffy, who owns the lot where the tools were found, called them "stunning and beautiful."

"I would never have imagined that these were 13,000 years old. I thought they might be from American Indians 100 or 200 years ago," he said.

Curiosity led Mahaffy to contact CU, and Bamforth made the short trip out to the house to investigate.

"My jaw just dropped," Bamforth said. "Boulder is a densely populated area. And in the midst of all that to find this cache."

Mahaffy's Clovis cache is one of only two that have been analyzed for protein residue from ice age animals, Bamforth said. Mahaffy paid for the analysis by California State University in Bakersfield.

A biotech entrepreneur, Mahaffy is familiar with the process. He is the former president and chief executive officer of Boulder-based Pharmion Corp., acquired by Celgene Corp. for nearly $3 billion in 2007.

The cache was buried 18 inches deep and was packed into a hole the size of a large shoe box. The tools were most likely wrapped in a skin that deteriorated over time, Mahaffy said.

"The kind of stone that's present — the kind that flakes to a good sharp edge — isn't widely available in this part of Colorado. It looks like they were storing material because they knew they would need it later," said Bamforth.

Bamforth believes the tools had been untouched since the owners placed them there for storage.

One hundred thirty centuries later, Mahaffy wants to donate most of them to a museum but plans to rebury a few of them in his yard.

"These tools have been associated with these people and this land for 13,000 years. I would like some of these tools to stay where they belong," he said. "I think there's a spiritual quality to it."