The dodo –just a big pigeon?

Despite its iconic status, we know very little about the evolutionary history of the dodo. Scientists have grouped the dodo with the pigeons in thefamily Columbidae since 1842, based on anatomical evidence. With the use of ancient DNA from dodo bones and modern moleculardata, scientists were able to confirm that the dodo is nested within Columbidae,together with the extinct Solitaire (Pezophapssolitaria) from Rodriguez island (Shapiro et al., 2002). The closest livingrelative to the dodo is the Nicobar pigeon, Caloenasnicobarica, which is found on small islands in Southeast Asia.  The analysis by Shapiro and coworkers suggeststhat the dodo and solitaire lineages split from Caloenasaround 42 million years ago. What happened after that split remains amystery, but by the time the dodo was discovered on Mauritius, it looked vastlydifferent from a Nicobar pigeon. The dodo had undergone a significant increasein size, lost its ability to fly, and developed an unusual skull with a massivebill. Although the first two phenomena are common, and often linked, in islandbirds, the highly modified skull of the dodo has us scratching our heads. Why, and how,would such a skull evolve in a pigeon?

 

Judge for yourself: dodo skull (left) and Nicobar pigeon(right) to scale.

Shapiro, B., Sibthorpe, D., Rambaut, A., Austin, J., Wragg,G.M., Bininda-Emonds, O.R.P., Lee, P.L.M., Cooper, A., 2002. Flight of theDodo. Science 295 (5560): 1683. doi:10.1126/science.295.5560.1683