Yes, I asked this question about a month ago, but didn't receive any responses. I've been trying to find information regarding the subject but can't seem to anywhere.
I don't mean when did humanity understand photosynthesis biologically. I mean when did humanity understand that soil and water were not the only two things needed for plant growth? I imagine that it was sort of a given that plants grew in soil and water, and that there is a distinct possibility that humans didn't realize that light had anything to do with it considering that the sun is just sort of there. I could be way off base though. Does anyone have information regarding this topic?
The sun has been associated with growth and fertility for as long as people have been writing about religion. The earliest evidence I can think of is the Pyramid Texts of Unas, a 5th Dynasty Egyptian king who ruled 2375-2345. They describe Re as a sun god who created himself and provides the deceased king with grains. Obviously, this isn't something we can set a firm date, so I"m interested in seeing older associations.