Hi, I have question about what the current state of evolutionary biology has to say about how complex biological structures form. I'll just illustrate my question with an example, and I apologize in advance for using the incorrect terminology - I have very little biology training. For me it's easy to understand how a trait like long necks in giraffes would be selected for and evolve. If having a long neck is advantageous, then whatever animals happen to have slightly longer necks, can collect slightly more leaves and will be slightly better off, and they are more likely to pass their long-neck genes on to their offspring. This is a gradual and continuous process, which occurs in small steps, and each small step helps the individual animal survive in it's environment and reproduce more effectively. This is the general process of evolution, and seems to be perfectly intuitive. Now, what I don't find as intuitive is how biological structures, such as the wing of a bird for example, are able to evolve. The reason being, I don't see how the intermediate steps from say a normal walking leg to a wing help the animal to survive. To me, a half evolved wing - something much less functional than a normal leg, and much less functional than a normal wing - seems like a very unlikely thing to be selected for. What possible path of small success steps could you take toward evolving a wing, that represents a continuous advantage to the animal? I'm using the example of a wing, but I'm sure there are far better ones. Thanks.