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U of T and ROM researchers publish new theory on origin of flightless birds

October 19, 2012

Two longstanding conflicting views may both be accurate

TORONTO, ON — New DNA stud­ies by Uni­ver­si­ty of Toron­to (U of T) researchers indi­cate that two oppos­ing views on the ori­gin of ratites, large flight­less birds orig­i­nat­ing on the south­ern super­con­ti­nent Gond­wana, might both be cor­rect.

Dr. Allan J. Bak­er, U of T ecol­o­gy and evo­lu­tion­ary biol­o­gy pro­fes­sor and Head of the ROM’s Depart­ment of Nat­ur­al His­to­ry and Oliv­er Had­drath, U of T PhD can­di­date and Research Tech­ni­cian with the Ornithol­o­gy Divi­sion, Depart­ment of Nat­ur­al His­to­ry at the ROM, stud­ied the ancient DNA of New Zealand moas (extinct flight­less birds), using mol­e­c­u­lar dat­ing. The study showed that three of the ratite lin­eages diverged at around the same time as the north­ern and south­ern con­ti­nents frag­ment­ed; how­ev­er, two of the lin­eages had sub­se­quent­ly flown to the con­ti­nents they now live on.

This study pro­vides impor­tant evi­dence to the ongo­ing con­tro­ver­sial debate on whether or not flight­less birds, such as the ostrich, emu, cas­sowary, kiwi, rhea or the extinct moa and ele­phant bird, are descend­ed from a once fly­ing ances­tor. Charles Dar­win thought that these ratites prob­a­bly flew to the south­ern con­ti­nents where they can be found today and lat­er inde­pen­dent­ly lost their pow­er of flight. How­ev­er, mor­phol­o­gists have argued that the com­mon ances­tor to these birds was already flight­less.

They believe that instead of fly­ing to the south­ern con­ti­nents, ratites like­ly float­ed on con­ti­nen­tal frag­ments as Gond­wana broke apart.

Past DNA stud­ies have sup­port­ed Darwin’s hypoth­e­sis. The fly­ing tinamou of South Amer­i­ca was found to be most close­ly relat­ed by DNA to the flight­less giant moa of New Zealand, mean­ing the com­mon ances­tor was most like­ly a fly­ing bird, as Dar­win had sup­posed.

Through mol­e­c­u­lar dat­ing, Bak­er and Had­drath were also able to date the ori­gin of mod­ern birds to the ear­ly Cre­ta­ceous Peri­od, which is much ear­li­er than the old­est fos­sils of mod­ern birds that have been dis­cov­ered to date. Fur­ther research into unex­plored places such as Antarc­ti­ca or sites where much old­er fos­sils have yet to be dis­cov­ered might pro­vide fur­ther insight into why both the­o­ries may be able to coex­ist.

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