This also raises the question, how did the Borg acquire the technology they
have? Generally speaking, in a competition, the higher technology will
win, especially when you are talking about phasers and shields and warp
drives. So the Borg should be unable to defeat an enemy with higher
technology than themselves. The only reason they are a threat to the
Federation is because they have better technology.
This means that they should not have been able to assimilate a race which
possessed their current technology if all they had was Federation-style
phasers or something weaker. Their ships would not have constituted a
threat to such a race.
I conclude that the Borg evolved as individuals (or at least in a state
where they could make technological progress) until they reached their
present level, *then* they formed the Collective as we see it, which has
stagnated technologically for some reason.
Of course, we all recognize that the Star Trek universe is a spectacularly
unlikely future, with their incredibly slow rate of technological
progress, lack of exploitation of nanotech, extremely limited medical
technology, under-utilization of AI despite its clear effectiveness, etc.
Hal