If you're a believer in science, you're probably at least vaguely aware that prevailing theories posit that the birds of today are distant relatives to the dinosaurs that died off millions of years ago.
Which makes sense! I mean, Jurassic Park, COME ON! Er...but it's actually a little bit weird because on the surface it's not clear how that works.
How exactly does a creature evolve feathers necessary for flight when there's no clear value to the incremental stages? You need all of the feathers to fly. Just a few won't do it. The archaeological record suggests that dinosaurs had feathers on their tails arms and heads for ornament and intimidation, but that doesn't provide a full explanation of how fully-feathered birds took flight.
Well, as the narrator explains starting at about 2:35 into the TED (yes, TED) video above, even just a few feathers would have given dinosaurs some lift when running, helping them run faster. This small advantage developed over millions of years could have evolved into flight. Sounds reasonable. [TED]