system
Given the following post, respond as if you're commenting on Reddit:
human
[Assassin's Creed] If ancestors' memories are imprinted on genes, why do we have access to ALL memories? (Further explanation inside)

The premise of the AC universe is that you are reliving a previous ancestor's life since their memories are encoded in their genes, and then passed on to their offspring.  However, each offspring should really only get half of each parent's DNA, so shouldn't they only receive about half of each parent's memories as well?  By the time all of these memories come to Desmond Miles, the memories should almost be unwatchable.

Now, there's an explanation that only half-works for me.  A huge percentage of what you do didn't actually necessarily happen in the ancestor's life... it's just a simulation put together by the Animus.  However, there are still sections that are confirmed to have happened exactly as depicted... which comes down to pretty much any cutscene, particularly the "on-the-death-bed" victim scenes.  But even then, I feel like DNA would give you bits and pieces of those scenes at best, not the entire thing start to finish.  Again, the number of times DNA splits from the late 1100's to 198x (Desmond's conception) should make these pretty much unwatchable.  So what's going on here?
gpt
So far, we've only seen memories from a male ancestor, passed onto a male descendant.  It's possible genetic memories are similar to Mitochondrial DNA.

Mitochondrial DNA is only passed from the mother, and as such, maternal lineage can be traced directly with it.  If genetic memories are similar, it could be the same phenomenon, but via DNA from the father.

The sheer amount of genetic material involved would be obscene after a few generations though.  In this case, it could be that only particularly important memories are preserved, the rest lost over time.  It could also be linked to the use of Eagle Sense/Sight/Vision, with memories formed (temporally) near the use of that ability being more strongly encoded.

This could explain why we never saw Altair's, Ezio's, Edward's, or Haytham's childhoods, but we did see Connor's.  Connor was closer to Desmond than the others (genealogically), and as he grew up in a less urban setting, he may have had more instinctual need for Eagle Sense, thus better encoding his younger memories.  His more tumultuous youth could also be a factor.