Posted: Oct 09, 2018 12:11 pm
Well, let's see. What sensory information would nerve cells on the skin have been hitherto receiving?
1. Temperature.
2. Pressure.
3. Taction.
A small cluster of photosensitive cells capable of responding to a few photons would likely not have provided any additional information that wasn't already being received. The signal would not be strong enough without appropriate amplification: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4160332/. Also, for it to be useful, the signals sent to the central nervous system would have to be differentiated and treated as new information such as the presence of light or shadow rather than any of the above. This requires a new interpretative mechanism, not just phototransduction. Sorry to burst your bubble.