Yes, but a very general idea.
The life-conditions would have required only relatively (i.e. compared to
later eras in evolution) sedate responses to adverse and opportune selective
("selective" not only of mutants, in a Darwinian sense, but of available
behavioural strategies/programs at the life-situational level of each
individual) challenges. So it would be one of the transmitters used by the
phylogenetically oldest "nonspecific" (system) type neurons of the central
nervous system.
[By the way, I prefer to label them "RAT [for loosely 'Reticular Activating
Type'] neurons. ;-) ]
Michael Chia wrote in message <7bh2bt$b7q at net.bio.net>...
>Anyone has any idea what the first neurotransmitter is?
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