“As to why we (and mice) would have a gene that makes it easier to forget, perhaps they should consider that while being locked into the memory of a maze may be advantageous to a lab raised maze walking mouse - it could be absolute MURDER for a wild mouse that has to adapt to changing circumstances and cannot be a slave to its memory.”
It’s hard to imagine that a better memory would not be an advantage for survival. Remembering not to eat certain things that made you sick or not doing to certain things that almost got you killed would be helpful. There must be other things the gene effects that on balance make it better to have in the wild.
The trick is to remember that a food made you sick, or that a place is dangerous, but not be so locked into the memory that you forgo advantageous behaviors because of an unfortunate memory.
Obviously there is a balance achieved in the wild between being able to remember, but not being a slave to the memory. You knock out this gene and the balance is thrown off, and you have a mouse that is MUCH better at memorizing a maze - but is it as adaptable to new circumstance, is it as ‘creative’ at problem solving - or is it locked completely into what worked or what didn't work previously?
So I guess what I am saying is that a mouse remembers good enough to do his mousy thing, a mouse isn't (in the wild) a maze walker, he is a mouse.
If a population of mice needed to remember things better or more viscerally or whatever - and this gene didn't have other features of antagonistic pleotropy (for any good thing it does it probably does bad stuff also)- then the natural tendency would be for this gene to be downregulated or rendered non-functional through selection of genetic variation.