Ostriches once flew

FAR-FLUNG: STUDY EXPLAINS HOW EMUS AND KIWIS CROSSED OCEANS

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How did the ostrich cross the ocean?

It may sound like a joke, but scientists have long been puzzled by how the family of birds that includes African ostriches, Australian emus and cassowaries, New Zealand kiwis and South American rheas spread across the world - given that none of them can fly.

However, a study published on Wednesday may have found the answer to this mystery: the family's oldest-known ancestors were able to take wing.

The only currently living member of this bird family - which is called palaeognaths - capable of flight is the tinamous in Central and South America. But even then, the shy birds can only fly over short distances when they need to escape danger or clear obstacles.

Given this ineptitude in the air, scientists have struggled to explain how palaeognaths became so far-flung.