Ireland simply lacked any wild cereal that could be domesticated, and other than the dog the only potentially domesticable animal was the wild boar. Moreover, as we will see, unless there is some 'push' or 'pull' factor, human societies are unlikely to develop agriculture on their own. This leaves essentially two different models that attempt to explain the origins of the Irish Neolithic: acculturation and colonization.
Acculturation places the primary impetus for the adoption of agriculture on the Mesolithic occupants of Ireland. It still acknowledges that there must have been an outside source that came into contact with Irish hunter-gatherers - an existing Neolithic population from whom the necessary techniques and domestic plants and animals could be acquired. Generally in Continental Europe we see this phenomenon operating between adjacent communities, e.g. a group of hunter-gatherers in, say, the Lower Rhine basin, living next to existing farmers, begins to acquire from them, perhaps through exchange, certain items of technology (polished stone axes, new chipped stone tools, the idea of manufacturing ceramics) and then, after more intensive interrelationships (perhaps intermarriage or theft) they also begin to adopt domestic livestock and ultimately domestic cereals.10 We believe we can see such a process, for example, in parts of Atlantic Europe, southern Scandinavia and eastern Europe. But when we attempt to apply this same model to Ireland we have to deal with an added complication - the Irish Sea.
The body of water that separates Ireland from Britain or from direct contact with the Continent complicates the issue considerably by once again introducing the problem of logistics. In order to sustain the acculturation model, one needs to create what Marek Zvelebil and Peter Rowley-Conwy called an 'availability phase', i.e. a halfway house contact area where the processes of transmitting the new economy can take place between existing farmers and their hunting-gathering neighbours." Obviously, this could hardly have taken place in the middle of the Irish Sea. Either Irish Mesolithic populations crossed, for example, to Britain or the Continent where they acquired domestic plants, animals and other elements of the Neolithic technology, or some British/Continental farmers must have established themselves in Ireland where they stimulated local hunter-gatherers to take up the new way of life.
In favour of a local Irish population acquiring the new economy themselves from across the water is their probable skill in seafaring based on their evident exploitation of both coastal and riverine resources.