Winged flight may be an accident of evolution

Ontario, New research undermines the ways scientists have previously attempted to explain the evolution of flight. Wings may have evolved for purposes other than flight, argues researcher Alexander Dececchi.

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In other words, winged-flight may be an accident of evolution — an evolutionary byproduct.

“By disproving the idea that the predicted models led to the development of flight, our research is a step towards determining how flight developed and whether it can evolve once or developed multiple times in different evolutionary lines,” Dececchi, a post-doctoral fellow at Queen’s University, said in a news release.

One of the most popular explanations for the evolutionary origins of flight is wing-assisted incline running, whereby bird-like dinosaurs and early flightless birds used wings to run up trees and cliffs to escape predators.

To test the potential for flight among early winged species, researchers analyzed the body mass and wing size of 45 specimens from 24 different non-avian theropod species, plus five early bird species. With modern birds as comparative models, researchers used the two anatomical indicators to estimate each specimen’s potential wing beat, flap angle and muscular output.

“We know the dimensions and we know how modern birds muscles and anatomy work,” Dececchi said. “Using our model, if a particular species doesn’t reach the minimum thresholds for function seen in the much more derived birds — such as the ability to take off or to generate a certain amount of power — it’s safe to say they would not have been able to perform these behaviors or fly.”

Researchers found that wing-assisted incline running was not associated with the anatomical thresholds necessary for the evolution of flight, nor did the behavior predict an improved chance of survival.

Signaling or sexual selection may offer a better explanation for the evolution of wings prior to their use for flight, Dececchi argued in his new paper on the subject — published this week in the journal PeerJ.

The new research also suggests disparate species — separated by millions of years and thousands of miles — may have independently happened upon winged flight. The adaptation may have evolved and died out many times over.

“There is some evidence that they evolved in parallel — there may be some differences in the details between how each taxon flew, but they tend to converge on these same answers,” concluded Dececchi. “That, to me, is one of the most exciting questions that has come out of the past few decades of work in theropods.”

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