NEW YORK, SEPT. 2 -- Scientists have discovered the earliest evidence of syphilis in the skeleton of a bear that lived in the Midwest 11,500 years ago, providing an important clue to the origins of the disease, it was reported today.

The skeleton, found by a public utility in Indiana several years ago, tested positive for antigens from bacteria known to cause syphilis, Dr. Bruce M. Rothschild, professor of medicine at Northeast Ohio University's College of Medicine, said.

Rothschild, an expert in the disease's history, tested the bones earlier this year and reported his results today in Nature, the British science journal.

"The bones had all the characteristics of syphilis," he said in a telephone interview. "But we couldn't be sure until we conducted the antigen test."

Antigens are substances foreign to the body, often proteins, that may be left behind by invading organisms.

Scholars have long debated the origins of the sexually transmitted disease, with most arguing that a syphilis epidemic in Europe in the early 16th century was brought by Christopher Columbus' crew returning from the New World.

Scientists have found evidence of syphilis in the bones of humans who lived 1,000 to 3,000 years ago on the North American continent, but the new discovery is the oldest sign of the disease.

Rothschild said humans and animals can share viral and bacterial diseases, pointing to a virus found in African monkeys that is similar to the virus that causes acquired immune deficiency syndrome in humans. He said some mammals are known to contract syphilis-like diseases but said there is no information about syphilis in modern-day bears.