It is often stated throughout the Stargate series that the Goa'uld are more technologically advanced, however, during the SG-1 episode "Pretense" (3.15), it is stated that the Goa'uld did not invent their technologies, but rather they assimilate them from the civilizations they take as host.
We know that the Goa'uld's original hosts were the evolved Unas, although we only see the primitive Unas, the "un-Goa'ulded" ones. IIRC, there was a distinction, and the evolved Unas were the ones taken as hosts.
Eventually, the Goa'uld take humans as hosts. The only way that could happen, and the way that's implied in the show, is that the Goa'uld traveled to Earth and abducted humans. This implies that the Goa'uld had space travel (and probably not just stargate travel), possibly the evolved Unas' space travel technology.
Is this accurate? Did the Goa'uld take over a technologically advanced Unas race and then trade Unas for humans? Were the full origins of the Goa'uld ever described in the Stargate series canon?