system
Given the following post, respond as if you're commenting on Reddit:
human
If humans achieve immortality, how would our brains cope with all the information over such a long lifespan.
gpt
We already learn new things partially by over-riding associations between other memories/skills/information. That's one reason why we might "forget" something. 

An important reason we are able to remember so much is memory consolidation. We form a network of associations between words, memories, etc. People don't store every single detail, only details that stand out, or are what neuroscientists call "salient" information. This allows us to re-create a memory from much less information than if we remembered everything in precise detail. When we try to remember, we re-create the story and make up a lot of the details based on our associations with that salient information.

There was a famous psychological experiment where participants read a story about a person driving up to an intersection. They were told that the driver saw a yield sign and stopped, looked both ways, then drove through the intersection. A while later,  participants were asked to evaluate whether statements about the story were true or false. One of them was "There there was a stop sign at the intersection." Turns out that virtually everyone "remembered" that there was a stop sign at the intersection.

If you rephrase the question and ask people "what was at the intersection?" they tend to either say they don't remember or that it was a yield sign. Simply posing the question as "There was a stop sign at the intersection" made people think of a stop sign, so when we try to remember we re-create the story with a stop sign in it. 

Point being that we don't really even remember all that information to begin with, we just remember enough to make the rest of it up.