Human tuberculosis may be 3,000 years older than previously thought, say researchers who analyzed DNA from 9,000-year-old human bones found off the coast of Israel.

"Examining ancient human remains for the markers of TB is very important because it helps to aid our understanding of prehistoric tuberculosis and how it evolved," said the study's lead author Dr. Mark Spigelman, of London's University College.

"This then helps us improve our understanding of modern TB and how we might develop more effective treatments."

Tuberculosis is caused by Mycobacterium tuberculosis bacteria that commonly attack the lungs, which killed an estimated 1.7 million people worldwide in 2006, according to the World Health Organization.

People who develop TB can often be cured provided that proper medical treatment is available. Rare but new drug-resistant strains require more potent and expensive medications that have more serious side effects.

In Wednesday's issue of the journal PLoS One, Spigelman and his colleagues described the bones, thought to be a mother and baby, that were found submerged in a 9,000-year-old Neolithic village off the coast of Haifa.

Infecting strain from humans, not cows

Prof. Israel Hershkovitz of Tel-Aviv University's anatomy department noticed the skeletons had bone lesions common in TB. Researchers then confirmed evidence of tuberculosis by analyzing DNA and cell walls from the specimens dating from 9,250 to 8,160 years ago.

"What is fascinating is that the infecting organism is definitely the human strain of tuberculosis, in contrast to the original theory that human TB evolved from bovine TB after animal domestication," said study co-author Helen Donoghue, also from University College.

The researchers were able to show that the strain of TB found in the skeletons had lost a piece of DNA making it identical to some of the strains infecting people today, Donoghue said.

Knowing that the deletion occurred 9,000 years ago gives scientists a better idea of the rate of change in TB and its long association with humans.

Previously, tissue samples from ancient gravesites and the examination of an Egyptian mummy suggested people were infected by tuberculosis as far back as 5,400 years.