to go upstream; to go up (a river); to go back (to the past or origin); to date back (to); to trace back (to)
going to the source; tracing to the origin
going upstream; sailing against the current
retroactivity; retroaction; being retroactive (to)
going upstream; swimming upstream
going upstream; sailing against the current
anadromous fish (fish that migrates upstream, e.g. salmon)