Fair points.

There are raised beaches in NI too, but they're still eroded away and much of them has been lost. A lot of inland habitation sites have been lost (or not found yet) too.

Although the analysis is fascinating I still can't help thinking it's skewed by many factors. Just the ever sceptical statistician in me I'm afraid looking for holes in data samples :-)

I think the biggest factor has to be that people were growing in number and moving inland to live. They would have had more access to land-based wildlife than the earlier shore/river following nomads of earlier times. One can assume that they may have traded red meat for fish with the communities that stayed by the sea and so even the shorefolk (for want of a better word for them) would have a red meat content in their diets. I would be amazed if these shorefolk abandoned fish completely (or near enough) though unless forced to by catastrophe.

The fact that proportionally more people were living away from water is bound to force a proportional shift away from fish.