Our shared ancestor scampered under dinosaurs' feet 130 million years ago. Credit: © Corbis

In paddocks across Australia, scientists are grooming a rabbit-sized kangaroo for its debut in international science.

If all goes according to plan, the tammar wallaby will join humans, mice and flies among the illustrious ranks of creatures to have their DNA read letter by letter. The researchers have just dispatched a bid to the US National Human Genome Research Institute (NHGRI) in Bethesda, Maryland, pleading with them to sequence the marsupial's genome.

The kangaroo tender is entering this month's round of a tri-annual competition between scientists' pet organisms. The winners will join the chimpanzee, honeybee and dog at the front of the queue for time and money in US sequencing centres.

The Australian team admits that the kangaroo's status as a national icon has partly fuelled their bid, but they also lack the resources to go it alone. "We're looking for a benefactor with a sense of Australian pride," says Jenny Graves of the Australian National University in Canberra, who is spearheading the kangaroo campaign1.

The team believes that kangaroo DNA will reveal valuable secrets about our evolutionary history. They hope to identify stretches of DNA that are unique to the human genome by comparing it with its marsupial counterpart ? 130 million years ago, our common ancestor scampered under dinosaurs' feet.

Scientists already carry out these comparisons with other creatures' DNA. But Graves argues that mammalian cousins such as the mouse share so much sequence with humans that critical regions might be missed. Fish and birds, conversely, are too distant relatives.

Kangaroos fill the gap ? they are mammals, but share only certain parts of our biology. They wear fur coats and suckle their young on milk, but unlike humans, carry their growing embryos in pockets rather than inside the uterus.

These characteristics place marsupials on a separate branch of the mammalian evolutionary tree ? far from the other mammals that are lining up to be sequenced. "It's the only one at that level of genetic distance from humans," says Steve O'Brien, who studies evolutionary genomics at the National Institutes of Health in Bethesda.

It's the only animal at that level of genetic distance from humans Steve O'Brien , NIH

Graves and her colleagues have already used kangaroo genetics to show that human sex chromosomes evolved from other standard ones. They hope to illuminate the origins of mammals' other genetic oddities, such as the imprinting process, in which a chemical stamp switches off gene copies from either the mother or the father.

The star of the bid, the pint-sized tammar wallaby, is the lab mouse of the marsupial world. Its reproduction has long been studied ? and it lives happily and cheaply on hay and grass.

But the kangaroo will face some tough competition in the genome contest. The cat, pig and rhesus macaque monkey are all expected to be in the running. And the NHGRI's genome-selection committee weighs up an organism's medical relevance and importance to agriculture as well as its evolutionary clout.

The final decision is expected in May. But Graves is so confident of the kangaroo's success that she is already plotting Australia's next foray into international genomics. "Next off the block will be the platypus," she says.