Evolution, not revulsion

Here is an interesting fact: the Dublin city centre seagulls have 42% less parietal cells than their mainland Europe counterparts. For those who weren't paying attention in secondary school biology (I was one of them), parietal cells are these wonderful microscopic devices in your stomach that produce the hydrochloric acid necessary to digest your food. 

So why are the Dublin seagulls so radically different? It's an evolution thing, and the answer is quite simple really: they function with almost half the number of parietal cells because most of the food they eat has been pre-digested for them.