Gill Hypothesis
The gill hypothesis suggests that ‘protowings’ first evolved in aquatic larvae to help in navigation (Gullan & Cranston 2010). As the insects left the water the wing structure didn’t help in flying but other functions such as protection of legs and thermoregulation (Gullan & Cranston 2010). The structures then slowly transitioned to gliding and other flight purposes (Gullan & Cranston 2010). There is evidence for this hypothesis in two ancient genes that exhibit a wing function that is found in the gills of crustaceans and insect wings (Klowden 2007).
The developement of a wing from a gill like structure to thin wing membrane. Image provided by Klowden(2007).
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Evolution of wings in relation to the gill hypothesis. Image provided by Klowden (2007).
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