The fossils were quickly excavated, jacketed in plaster, and shipped to a nearby lab for ongoing cleaning and analysis so that construction could continue. Among the largest and most complete specimens in the new collection are a giant ancestor of the saber-toothed tiger, ground sloths the size of grizzly bears, two types of camel, and new deer and horse species. “It was extremely exciting to come across such a rare find,” says Philippe Lapin, one of the paleontologists with the Southern California Edison team. “The number of fossils was beyond our expectations,” he says. Thomas Demere, curator of the department of paleontology at the San Diego Natural History Museum, says that because these fossils are from an earlier epoch than most others found in the region, they will “help flesh out the tree of life here with what organisms existed, when they arrived, and how they evolved.”
If not for the strong California laws protecting paleontological resources at the site, the San Timoteo discoveries might never have happened. Most of us think of determined bone hunters digging
up paleontological treasure on dedicated expeditions in exotic locales, but the fact is that many fossils turn up quite by chance.
Construction projects, which sift through tremendous amounts of dirt and rock while digging foundations or laying roads, are an especially rich source of these happy accidents. In 2009, for instance, builders erecting a seawall in Santa Cruz, California, uncovered three whales, two porpoises, and other marine life from 12 million to 15 million years ago, while a recent expansion of the Caldecott Tunnel near Berkeley, California, yielded extinct camels, rhinos, and giant wolverines. In 2006 construction for a parking garage for the Los Angeles County Museum of Art revealed a prehistoric lion skull, dire wolves, and a near-complete mammoth skeleton from the last Ice Age, roughly 40,000 to 100,000 years ago. And last October, a bulldozer operator working on a reservoir expansion project in Colorado found a juvenile mammoth.
Subsequent excavation in Colorado exposed at least eight mastodons, three more mammoths, extinct bison, and a 9-foot sloth; researchers hope to return to the site to continue digging this spring. “We find fossils about 85 percent of the time on construction sites,” says paleontologist Lanny Fisk, president of PaleoResource Consultants, an Auburn, California, outfit that specializes in preserving fossil remains. Fisk and other paleontologists estimate that more than half of all new fossils in the country come from construction sites, and in states like California with powerful regulations, that figure may be as high as 70 percent.