Tuesday, September 09, 2008

Flightless Birds Not Closely Related

According to a new study, large flightless birds (ratites) are not closely related but instead evolved independently of each other. This study grew out of the large scale Tree of Life project to understand bird evolution through DNA. The sequenced genetic material for that project indicated that many flightless species seemed more closely related to flighted species than to each other. The current study delves into those relationships in more detail.

Scientists assumed that a single flightless common ancestor of the ratites lived on the supercontinent of Gondwana, which slowly broke up into Africa, South America, Australia and New Zealand; once divided, the ancestor species evolved slightly in each new location to produce the differences among the present-day ratites, Braun said.

But in light of this new information, he said it's more likely that the ratites' ancestors distributed themselves among the southern continents after the breakup of Gondwana, which began about 167 million years ago, in a much more obvious way.

They flew.
The current study does not answer why these birds each evolved flightless features.