we do. the transitional species for humans was when we evolved to walk on two legs (remember lucy). if you look at the skeletons, you can definetly see the growth overtime.

as for transitional species, there are fish with legs. i'm not sure where you get reptiles w/wings, but i'll drop that.

darwin got his ideas when he vistied the galapagos. he noticed that the same species had traveled to different islands but had slowly started to evolve away from each other. its in action today. one good example is the vampire birds (i believe in the galapagos also). we have their relatives in other places, but they have adapted on the galapagos to suck the blood out of other birds (well, they bite them w/their beaks and eat up). after having them cataloged for some time now, scientists have noticed there beaks have actually gotten smaller and thinner, better to do their job.

evolution is only a theory in the sense that we don't know everything about it. but look around you, its everywhere. i could explain myself more, but my mom taught me to not waste my energy, i will never get people to change their mind.