In evolution, the current uses of a given structure or molecule is not necessarily an indication of what it originally evolved for, and in this case, whatever p

In evolution, the current uses of a given structure or molecule is not necessarily an indication of what it originally evolved for, and in this case, whatever plants have been doing with serotonin and dopamine, it is not as neurotransmitters. When animals began to evolve neural systems, presumably these already-present molecules proved useful as neurotransmitters. The fact that ctenophores use a different set of neurotransmitters is taken by Moroz as strong evidence that neural systems evolved more than once - and furthermore, according to the article, "Moroz now counts nine to 12 independent evolutionary origins of the nervous system" on the basis of other differences. In this view, ctenophores are the last representatives of one of those alternatives. I wonder if Moroz is harming his case by stretching it too thinly -- small differences do not necessarily require independent origins -- but I am not a biologist.