A large cat dining on the entrails of one of a human hundreds of thousands of years ago contracted an ulcer-causing bacterium that spread to lions, cheetahs and tigers that persists to this day, a new study concludes.
According to theory, an ulcer-causing microbe diverged after a human ate a cat infected with the ulcer-causing bacteria or a cat ate an infected human.
To determine who or what ate whom, the researchers compared the genomes of the two bacteria species.
They found that many of the inactive genes in H. acinonychis, the species that infects large cats, are more fragmented than their still-functioning counterparts.
This strongly suggests that the direction of the host jump was from humans to cats and not the other way around, the researchers say.
Based on similarities in the genomes of the two bacteria species, the researchers estimate that the host jump from humans to large cats took place about 200,000 years ago.
The finding will be detailed in an upcoming issue of the journal PLoS Genetics.
Posted: June 29, 2006, 5:00 a.m. EST