Re:
It is beyond me how anybody thinks they can define advantage. Unless I misunderstand, the fundamentalist Darwinists, who seem to believe something different from Darwin, are nuts to expect to find application for systematization where they think it exists.
Like you, I find no particular attraction to the fundies. I have no problem with advantage, but it is a VERY retrospective process. It is also one where it is possible to lay the "advantage" at the feet of a single individual. Truth of the matter, I think there is very little place for the individual in Darwin's theory. But as this is an opinion from a non-academic, so it is lacking the rigor required of an authority.
Advantage
is established several generations after the "patient-zero"
shuffles off this mortal coil. The means of establishing
"advantage" is the simple expedient of counting the
offspring and offspring's offspring and comparing the raw
number of living descendants. Not hard at all. The trouble
is that it is rarely done in a systematic and controlled
manner (read here: outside of a lab and with either fruit
flies or something like e. coli it has never been
done (that I am aware of)). The really hard part is teasing
the supposed "trait" that confers the "advantage" away from
the myriad other traits that compose an individual and/or a
species.
Unlike you, I find the idea behind Darwin to be compelling. But, like the previous faith that natural selection sought to dislodge (read here: The Bible), it was just turned to political posturing and status competition. Scientists have talked their way into being the new priests, and like priests, they have mucho problemo with folks not thinking right. The default position for a scientist/priest is on a podium, denouncing the heretics who dare to not parrot the correct dogma.
Like most
central tenets of any faith, natural selection has been
larded with non-canonical addenda.