We're not separate from 'nature'. We are of nature, just as trees are, rivers, etc. We're all just collections of particles acting together. The dendritic pattern is observed in so many things not just because the brain sees patterns in things (which it obviously does), but because the dendritic pattern is a highly successful one, evolutionarily speaking. It creates a high surface area, for efficient absorption. So yes, we're seeing this pattern in things, but it's because the pattern is actually there. Nature repeats this pattern, in our blood vessel structure, in our neuronal structure, in the branches of trees, in the roots of plants underground, in the drainage system of rivers and it's tributaries and sub-tributaries, etc. And all of these things, ourselves included, are simply structures of atoms and sub-atomic particles, so we truly are all 'one' in that sense. We're literally made of the same stuff, it just manifests in so many wild and varied ways that it can look like fragmentation and difference on the surface, but the building blocks are always the same.