>> There have been no studies of large groups of people who have followed the currently popular versions of the Paleo diet for decades to assess their long-term health effects.

> You could say similar things about climate change. The science is, and always will be, out. That's the nature of science.

This is a false equivalency.

Science requires experiments to support or refute hypotheses. The fact that new experiments may cause us to revisit a theory does not mean that one can assert any arbitrary theory to be correct.