In an experiment to test the __________? hypothesis for the origin of wings, researchers probed the developing limbs of brine shrimp (a living member of an ancient lineage of crustaceans) for the presence of tool-kit genes called nubbin and apterous. a) gills to feathers (hypothesis). b) gill co-option (hypothesis). c) wings-from-thorax (hypothesis). d) gill arch (hypothesis). e) independent gill (hypothesis)..