Verb (5-dan, る, intransitive)
Usually written in kana
1. to go upstream; to go up (a river)
この川を遡ると湖に出る。If you go up this river, you come out at a lake.
2. to go back (to the past or origin); to date back (to); to trace back (to); to be retroactive (to)
ならば原因を遡ってみるとしよう。Then, let's try tracing back the cause.