We have looked at the final solutions so far of nature and flight. However, they had to have a beginning somewhere. There were two theories about how flight evolved around the time of dinosaurs. The first was that flight evolved from dinosaurs running very fast, and then eventually became more and more aerodynamic, and finally took to the skies. This was the ground-up theory. The other one was that flight evolved from the tops of trees down. That gliding came first, and then over time powered flight was achieved. In 2003 a new fossil was found that would eventually decide what theory was correct.
The fossil was that of the Microraptor. This unique creature had feathers, but maintained some of its dinosaur looks. It had a wingspan of about one meter, and weighed only 1kg (2.2lbs). The interesting thing was that this animal had two sets of wings. With this extra set of wings it was debated whether they were used for powered flight, or if they were simply for gliding. A study found that the four wings were actually physically incapable of powered flight. They concluded that it could only glide, and that the Microraptor would glide over 40 meters.
The same study found that if the Microraptor was to jump from a tree, it would have to land on another tree, because it would not have survived if it hit the ground. It seems that the debate has been concluded. Flight started with animals gliding from one tree to the next.
Soon after the Microraptor there was a shift in evolution from four wings to two wings. However, the Microraptor is believed to still be an ancestor of the modern birds.
Jacqui Hayes. Bird Wings Evolved from Biplane Dinosaurs, 2007. 17 Oct. 2011.
Nova. The Four-Winged Dinosaur, 2008. 17 Oct. 2011.