A treasure trove of Coast Miwok Indian life dating back 4,500 years — older than King Tut's tomb — was discovered in Marin County and then destroyed to make way for multimillion-dollar homes, archaeologists said.

The American Indian burial ground and village site, so rich in history that it was dubbed the "grandfather midden," was examined and categorized under a shroud of secrecy before construction began this month on the $55 million Rose Lane development in Larkspur, Calif.

The 300-foot-long site contained 600 human burials, tools, musical instruments, harpoon tips, spears and throwing sticks from a time long before the introduction of the bow and arrow. The bones of grizzly and black bears were also found, along with a ceremonial California condor burial.

More than a million bones

"This was a site of considerable archaeological value," said Dwight Simons, a consulting archaeologist who analyzed 7,200 bones, including the largest collection of bear bones to be found in a prehistoric site in the Bay Area. "My estimate of bones and fragments in the entire site was easily over a million and probably more than that. It was staggering."

All of it, including stone tools and idols apparently created for trade with other tribes, was removed, reburied in an undisclosed location on the site and apparently graded over, destroying the geologic record and ending any chance of future study, archaeologists said. Not a single artifact was saved.

Lost forever was a carbon-dated record in the soil layers of indigenous life going back approximately to the time the Great Pyramid of Giza was built in Egypt. It was, several prominent archaeologists said, the largest, best-preserved, most ethnologically rich American Indian site found in the Bay Area in at least a century.

"It should have been protected," said Jelmer Eerkens, a professor of archaeology at the University of California, Davis, who visited the site. "The developers have the right to develop their land, but at least the information contained in the site should have been protected and samples should have been saved so that they could be studied in the future."

The shell mound was first documented in Larkspur in 1907, but no one knew its significance until a developer decided to build homes, prompting an examination of the grounds.

The development was approved by the city in 2010, but the developer, Larkspur Land 8 Owner LLC, was required under the California Environmental Quality Act to bring in archaeologists to study the shell mound under the direction of American Indian monitors before it could build.

The developers hired San Francisco's Holman & Associates Archaeological Consultants to conduct an excavation, and that firm spent the past year and a half on the site, calling in 25 archaeologists and 10 other specialists to study aspects of the mound. As required by the environmental act, the work was monitored by the Federated Indians of Graton Rancheria, who were designated the most likely descendants of Larkspur's indigenous people.

'A colonial view'

The American Indian leaders ultimately decided how the findings would be handled, and they defended their decision to remove and rebury the human remains and burial artifacts.

"The philosophy of the tribe in general is that we would like to protect our cultural resources and leave them as is," said Nick Tipon, a longtime member of the Sacred Sites Protection Committee of the Federated Indians of Graton Rancheria. "The notion that these cultural artifacts belong to the public is a colonial view."

But Eerkens and several other top archaeologists said a lot more could have been done to protect the shell mound. The problem was that the work was done under a confidentiality agreement, so little was known about it until March, when some of the archaeologists discussed their work during a Society for California Archaeology symposium in Visalia.

It was too late by then to preserve the site and, by all accounts, the archaeologists at the symposium were stunned.

"In my 40 years as a professional archaeologist, I've never heard of an archaeological site quite like this one," said E. Breck Parkman, the senior archaeologist for the California State Parks. "A ceremonial condor burial, for example, is unheard of in California."