An interesting test for secondary flightlessness would be to see if a flight-oriented brain existed in an animal that could not fly. If, as some assume, *Archaeopteryx* was not capable of powered flight, this may very well be a key piece; Paul, however, I know beleives Archie to be a powered flier. If something that is know for control in a 3D environment (say, flying or swimming, or possibly arboreal) exists in an animal that does not in fact seem capable of being in that environment (ie., it is terrestrial), it would appear to suggest either a part of a step-wise increase in such features from one environment to another, or a decrease/reversion/loss series.