CAT Scan Digs, Finds No More Ice Age Bones
The chunks of earth got curious looks Friday as they were wheeled through the clinic with flashing cameras in tow. Inside the sterile and pastel-colored CAT scan lab, a technician recorded the patient’s name in a computer: Arlington Springs Woman. Her age: 13,000 years old.
Scientists interested in the remains of an ancient woman who lived on the Channel Islands made certain Friday that two thigh bones are all they have to reconstruct a life lived at the end of the last major ice age.
With a doughnut-shaped machine normally used to X-ray humans for trauma, spinal injuries and cancer, staff members at Santa Barbara’s Sansum Medical Clinic scanned two blocks of compacted earth excavated 40 years ago from a gully on Santa Rosa Island. The blocks contain, a team of scientists believes, the oldest human remains ever found in North America.
As suspected by anthropologist John Johnson, who had already studied two pieces of thigh bone taken from the clay, the bony fragments peeking out of the chunks were a kneecap, or patella, and a 15-centimeter section of thigh bone, or femur. By adding that piece to a second piece from the same femur, Johnson determined the ancient woman stood between 4 feet, 11 inches and 5 feet, 2 inches tall.
Johnson, the Santa Barbara Museum of Natural History’s curator of anthropology, was keeping his fingers crossed that the CAT scan would reveal a skull within the dirt, or a pelvis, which would show whether the woman ever gave birth. But, he said, finding two more pieces of Arlington Springs Woman’s leg was still progress.
“Our goal was just to answer what else might be in these blocks of earth,” Johnson said. “We now know that it was all there when it was originally found.”
Forty years ago, archeologists discovered the remains in the Arlington Canyon area of Santa Rosa Island. They tested the bones but left them in their original dirt and encased them in plaster for future archeologists to examine and date as technology improved.
In March, a team of scientists announced radiocarbon dating had determined that leg pieces excavated from the clay blocks in 1993 are probably 13,000 years old--1,400 years older than previously thought and old enough to make them the oldest human remains ever found in North America.
Using the CAT scan Friday was a way of looking for more remains without breaking into the soil that protects them. A living human’s skeleton would glow white on the X-ray machine’s gray monitor, but Arlington Springs Woman’s fragile bones turned up black.
“What we’re seeing really is air in the bone, as opposed to what we normally see, which is dense calcium,” radiologist Cynthia Withers said. “Obviously over time, those minerals have washed away.”
The blocks also contain the tiny bones of an extinct species of mouse.
Now sure that no more of Arlington Springs Woman’s bones lie within the chunks of earth and confident that any other remains were destroyed or washed out to sea, researchers can pore over the bones they have already excavated for DNA.
A search five years ago failed to turn up any DNA, but Johnson hopes improvements in technology since will uncover genetic material that could be compared with modern DNA.
“It would tell us if she’s related to the American Indian or whether this is a genetic lineage that later went extinct,” he said.
