I would argue that there is evidence that the reindeer, the dog, and the horse were domesticated by non-agricultural cultures, peoples that had very little exposure to populations that utilized agriculture. What is your definition of civilization? I would argue that cultures can become more socially and technologically complex without agriculture. There was trade, for instance, before the neolithic revolution, of luxury items and resources like valuable shells or ornaments or stones. You don't need agriculture to invent the flute, for example, we've found flutes dating before the neolithic revolution, and if you have the flute you can invent music. We also have found boats being used by certain cultures before they adopted agriculture. Actually, you might be able to create a sedentary civilization based on the boat-making and fishing industry. They would have to be supplemented by trade from nomadic peoples, but they would have good reason to stay in one place.
The question then is, if a culture develops a sedentary society based on fishing and coastal trading, wouldn't it be a very simple matter for them to discover agriculture at that point? If the right plants are around? If people are living much of their lives in one location and have very few options for food, I think they would discover agriculture pretty quickly.
In saying all this, I have to admit that agriculture is incredibly useful, perhaps the most useful technology humanity has discovered, so if humanity goes without it their technological and social development is going to be retarded in a huge way. But that doesn't mean that some technological/social development isn't possible.