Ostriches, emus, kiwis and other ratites inherited flightlessness from one flightless common ancestor.

Ostriches, emus, rheas and kiwis share conspicuous features associated with life on the ground. For much of the late twentieth century, a leading explanation traced them to a single flightless ancestor. The breakup of the southern supercontinent Gondwana seemed to explain why their descendants lived on widely separated landmasses.

DNA complicated that tidy story.

A 2008 study compared 20 nuclear genes and placed tinamous, which can fly, within the traditional ratite group. Later work including extinct moa found that these New Zealand giants were especially close to South American tinamous. In 2014, ancient DNA linked Madagascar’s elephant birds to New Zealand’s kiwi.

These relationships support a different reconstruction: flying ancestors could disperse, and separate lineages later lost flight. Similar body plans need not all have been inherited from one already-flightless ancestor.

The birds still share common ancestry. What changed was where flightlessness arose within their family tree and how geography helped shape it. Researchers continue to refine the number and timing of losses. Regaining flight is a logical alternative for some tree arrangements, but repeated loss fits the broader evidence better.