Right, but the point is that certain plants and mammals do produce these independently. Humans don't require smoking weed to get enough cannabinoids into their

Right, but the point is that certain plants and mammals do produce these independently. Humans don't require smoking weed to get enough cannabinoids into their system to get their brain to actually work. Likewise poppies aren't stealing humans' opiates to defend against fungi. Both sets of species are each doing a whole bunch of work to create these very specific, very complex molecules, and using them for different purposes.