Large flightless birds are scattered across all but one of the world's southern continents. Since Darwin's era, people have wondered: How are they related?

At about the same time, another biologist, Richard Owen, assembled the remains of a giant ostrich-like fossil skeleton, the first extinct moa known to the western world. But a pesky detail puzzled Huxley: Small, ground-dwelling South American tinamous didn't seem to fit neatly with the ratites or other birds.

Tinamous fly, albeit reluctantly. And they possess keeled sternums, suggesting that they evolved with flying birds. But their palate bones match the ratites. Where do they belong?

Scientists have debated this question for 150 years. Now, a new study in the journal Molecular Biology and Evolution, analyzing