Fanciful scenarios
There is, as we have seen, not a scrap of fossil evidence to support this confidently stated sequence of events. Similarly unfounded guesswork surrounds the origin of flight. Thus the Encyclopaedia Britannica tentatively suggests that insects learned to fly because 'wings arose as fixed planes extending sideways from the thorax and were used, perhaps in some large leaping insect, for gliding. Later, muscles developed, first to control inclination and then to move the wings in flapping flight.'6
As for dinosaurs, their ability to fly is supposed to have come about because primitive swamp-dwelling reptiles, like crocodiles today, had developed strong hind legs and tails primarily for swimming. When the swamps dried up, they came on land to hunt food, where their pre-adapted legs enabled them to sprint short distances. Gradually they became two-legged, up-right runners. Some remained on the ground to form the dinosaur populations. Others, 'with arms freed from the burden of support and locomotion, took to gliding and developed a flap of skin stretching between arms and trunk'7 After gliding, they learned to flap their wings, and to fly.
The supposed history of bird flight runs on much the same lines - tree-climbing led to gliding and then to proper flight. As for bats, honest bafflement is once more the order of the day. No standard explanation exists, only a frustrated amazement.
On the subject of flight, it is notable that a number of zoologists and biologists weaken their attachment to the gradualism that Darwin insisted upon. George Simpson wrote that the early stages of evolution of the bat wing 'must have been many times more rapid' than after it had become fully formed8; which is really another way of saying that there was an inexplicably fast first stage, followed by fifty million years during which the bat wing didn't evolve at all. In the same vein, a dinosaur textbook says that the ancestors of pterosaurs ‘already possessed a fast-metabolizing physiology’ which made the transition to flight possible, after which things remained more or less stabler.9
