As far as I know, biology has no anthropic principle, but if it did, it might say that green fluorescent proteins (GFPs) evolved so that biologists could clone it out of jellyfish and into just about any other type of cell for use as a near-ideal reporter gene.
But the more relevant principle is the Cnidarian principle, which says that since GFP evolved in jellyfish, jellyfish must be using it for something. And no one really knows what that something is.
The mystery got more complicated a few weeks ago, when a group of chemists at the Shemiakin-Ovchinnikov Institute of Bioorganic Chemistry showed that GFPs are not just “passive light absorbers/emitters”, but can also be photo-activated reducing agents for biological molecules like NAD+, flavins, and cytochrome c.
First, it’s amazing that no one noticed this property of GFP before. Its safe to say that tens of thousands of researchers, including me, have used and studied some kind of GFP variants in the last few decades. And we all missed seeing this fundamental property of GFP.
Second, it raises the question of how important this newly discovered aspect of GFP might be to the natural biology of jellyfish and other organisms. I hope to have more to say on this second topic in the near future.