The rhesus macaque: 93% like you and me.Getty

In some ways, macaque monkeys are a lot like people: they can reside in cities, eat everything from peanuts to ice cream, and prefer to live in communities. Research published today will help scientists to figure out any genetic reasons behind these similarities — and behind our differences, from the macaques' short size and hairy bodies to their vulnerability to disease.

Writing in the journal Science¹ today, researchers present the DNA sequence of the rhesus macaque, a species of monkey living all across Asia. Old-world monkeys such as the macaque are thought to have diverged from the primate line that led to humans some 25 million years ago (see 'tab/437050aF1.html">Evolutionary relationships among the higher primates') . But an in-depth study of portions in the new sequence reveals that we are still 93% identical in our DNA.

Knowing the sequence of the macaque genome is important to scientists because captive-bred macaques are often used in tests of experimental drugs and medical treatments. Understanding how they differ from us should help to better predict when a drug will have a different effect on humans than it did in animal tests. But the macaque sequence is also exciting for scientists because it should help them learn more about what makes us human.

Compare and contrast

"When you sequence the genome of a non-human primate, you open the door to understanding the biology of an animal that's really closely related to us, and that's very exciting," says George Weinstock of the Baylor College of Medicine in Houston, Texas, a leader of the macaque sequencing effort.

Scientists sequenced the chimpanzee, a much more recent relative and closer cousin of ours, in 2005, showing that we are 98% identical in DNA. The macaque genome provides a third reference point in comparing these two. So, for instance, if scientists find a DNA difference between humans and chimps, they can check it against the macaque sequence to figure out whether the chimp or the human carries the more ancient version of the DNA.

By performing such comparisons, scientists hope to be able to home in on regions of the genome that contributed to the evolution of humans. This method will become even more powerful over the next few years, as scientists add other non-human primate genomes to the mix: the gibbon, the marmoset, the orangutan and the gorilla are all on the cards.

Sweet tooth

The macaque genome has already provided some insight into evolution.

One gene group that has massively expanded in the macaque, as compared with the human, is important to sugar digestion. Perhaps this is a genetic adaptation that allowed macaques to start eating a fruit-heavy diet, the researchers speculate.

The scientists' analysis also points out that many of the types of genes that differ between macaques and humans are found in our immune systems, which orchestrate our bodies' defences against disease. By studying these differences, scientists might be able to fine-tune their use of the macaque as a stand-in for people in medical experiments.

"Having a macaque genome means they can be used more wisely in research," Weinstock says.

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• References

  1. Rhesus Macaque Genome Sequencing and Analysis Consortium. Science, 316 . 222 - 234 (2007).