Gliding mammal linked to humans


Nov 2, 2007

A gliding mammal that lives in the forests of south-east Asia is our closest relative after apes, monkeys and lemurs, a DNA study shows.

Colugos are the "sisters" of primates, sharing a common ancestor some 80 million years ago when dinosaurs had their heyday, say US scientists.

Until now, many experts thought tree shrews were closer to primates.

Writing in Science, the team calls for urgent action to decipher the full genome sequence of colugos.

Colugos are known colloquially as flying lemurs; despite this they do not fly and they are not true lemurs.

Bat-like in appearance, and the size of a large squirrel, they use a special fold of skin to glide from tree to tree in tropical rainforests.

Rare mutations

An international team took a two-pronged approach to investigating the evolutionary origins of these shy, nocturnal tree-dwellers.

They looked at genetic "mistakes", or mutations, in the DNA "letters" of the genome sequence of primates, colugos and tree shrews - the animals that are most alike.

After comparing the three groups to about 30 other mammal species, they found that primates and colugos shared seven genetic changes that were very rare in other mammals.

In the second study, researchers used computer programs to search for similarities and differences in 13,000 DNA building blocks from five close animal groups - primates, the colugo family, tree-shrews, rodents and the order that includes hares and rabbits.

The research revealed that colugos and primates are more closely related than tree shrews and primates, solving a decade-long debate.

"This study resolves a long-standing question to primatologists and mammalologists on who the closest relative of primates was," co-author William J Murphy of Texas A&M University told BBC News.

"This will help us better interpret early primate evolution and those changes at the DNA level and in skeletal appearance that led to modern primates and ultimately to the human lineage itself."

The research team wants this new knowledge to be used to ensure that colugos have their full genome sequenced rather than only a less complete "draft" sequence as planned.