An international team of researchers has deciphered the genome of the rhesus macaque, one of the most widely used primates in medical research because it is susceptible to many of the same diseases that attack humans.

Coming only two years after the sequencing of the chimpanzee genome, the feat, reported today in the journal Science, provides new insight into what makes humans human.

“It allows us to learn what has been added or deleted in primate evolution from the rhesus macaque to the chimpanzee to the human,” said geneticist Richard A. Gibbs of the Baylor College of Medicine, who led the team.

The macaque genome joins a growing list that now includes not only humans and chimps, but also mouse, rat, dog, cow, honeybee, sea urchin, roundworm and yeast genomes.

The human and chimpanzee lineages diverged only about 6 million years ago and their genomes are 99 percent identical. With just the two genomes to study, it has been difficult to tell which human genes have been conserved through evolution and which have changed since the split.

By expanding the comparison to the genome of the macaque, which diverged from the human-chimpanzee lineage about 25 million years ago, much more information becomes available, Gibbs said.

Macaques and humans share about 93 percent of their genetic information.