In today's edition of the journal Science, the researchers report deciphering the macaque's DNA and comparing it with the genetic blueprints of humans and chimpanzees, the closest living species to humans .
Among the most intriguing discoveries : a list of diseases where the genetic mutation that makes people ill seems normal for the macaques.
"That is really quite a stunner," said Dr. Francis Collins, genetics chief at the National Institutes of Health, which funded the research. "It gives you a glimmer of how subtle changes in DNA cause big trouble."
The mapping of the human genome in 2001 sparked an explosion of work to decipher similarly the DNA of other animals, so scientists could compare species to try to understand the functions of various genes.
The rhesus macaque is the third primate genome to be completed, work that promises to greatly enhance the understanding of primate evolution, perhaps even to help explain what makes us human.
Not surprisingly, the DNA of humans, chimps, and macaques are highly similar. Humans and chimps have evolved separately since splitting from a common ancestor about 6 million years ago, but still have almost 99 percent of their gene sequences in common.
Macaques branched off from the ape family tree far earlier, about 25 million years ago -- yet share about 93 percent of their DNA with humans, the new work shows.
Here's the key: Six million years isn't long in evolutionary history. So if a particular gene is different in the human and the chimp, it's impossible to know which version came first. Add these more ancient Old World monkeys into the mix, however, and it may be possible to tease out genetic changes that were important for key traits of modern humans, such as higher brain power and walking upright.
But right away, 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 the monkeys are used as models of many human diseases, most notably the AIDS virus.
"As models, we expect them to behave like us," noted Gibbs.
