New analysis traces group’s origins to South America
The kangaroo’s twisted marsupial family tree is now in order thanks to — you guessed it — jumping genes. Genetic evidence shows that a South American ancestor gave rise to all Australian marsupials, and that the South American opossums were the earliest group to branch off from the other six marsupial clans.
Distinctive for raising their live-born young in protective pouches, marsupials all trace back to a common ancestor that split off from the rest of the mammals about 130 million years ago. But fossil and genetic evidence conflict about which marsupial species evolved first, and where.
Jumping genes provide new clues for solving the puzzle. These “junk” bits of DNA make copies of themselves to reinsert randomly in the genome. Half of the marsupial genome consists of jumping genes, so researchers have plenty to work with. Gene-jumping is rare, and each jump is a unique event unlikely to happen again. So if two species share a jumping