Scientists have unraveled the DNA of the rhesus macaque monkey, with the surprising finding that diseases where the same genetic mutation that makes people ill, seem normal for the macaques, despite the fact that they share about 93 percent of their DNA with humans.

The work raises some important biomedical questions, because rhesus macaques are ubiquitous in medical research. Most vaccines and many drugs are tested in the monkeys before ever reaching people. And they’re used as models of many human diseases, most notably the AIDS virus.