The colugo or flying lemur

The colugo, a southeast Asian mammal that resembles a flurry kite when it glides from tree to tree, has been found to be the closest surviving kin of the primate group to which humans belong.

A team of researchers from the US and Germany, led by William Murphy of the Texas A&M University, decided to bestow this honour on colugos after gruelling molecular and genomic studies. The finding, announced in the November 2 issue of Science, finally settles the dust on a topic that has been hotly debated over the last 10 years.

The colugo — which looks like a cross between a bat and a squirrel — is nicknamed “flying lemur” as it glides on sheets of skin, but it is neither a lemur nor does it fly.

While a section of scientists had earlier argued that the group Scandentia — which includes the small tree shrew that scampers up and down trees in Asian forests — fits the bill, others felt that the honour should go to dermopterans, a lesser-known group that includes two living species of colugos in southeast Asia.

“Determination of the closest living relative of primates has important ramifications for anthropology and genomics,” said Murphy, a professor of veterinary integrative biosciences.

Since 1999, all the three groups — primates, scandentians and dermopterans — have been recognised as comprising a single taxonomic unit known as Euarchonta or “true ancestors”. But the exact evolutionary relationships among them have proven to be elusive owing to their overall closeness and the existence of a number of shared features.

To resolve the ancestral relationships among primates and their closest relatives, the scientists compared alignments in recently sequenced genomes of multiple species, looking for rare genomic changes which would suggest the evolutionary branching patterns between species. This gave them a clearer, more accurate view of how primates evolved. The work, the scientists hope, would help in placing fossil primates and their relatives on the evolutionary family tree.