I have been thinking about this for quite some time. Apparently, according to some research, the human brain has an estimated total memory of around 2.5 petybites. This is not much of a issue right now, for that is more than enough space for one human lifetime. But, the question does have some merit. This is in-part due to the fact that human lifespans have been increasing rabidly over the last few decades. Because we might someday become biological immortal, the question does arise: since the human brain is not limitless, what will happen when that limit is reached? As far as I know, we would never have had to evolve a biological system to deal with this sort of problem. What might happen to a person physically once this limit is reached, and what could we do to prevent this from being a problem for future humans?
Is “we forget stuff” not sufficient?
The great majority of things that we experience don’t go into storage at all. And most of those that do, we forget completely within a fairly short space of time. I remember the route I took around the aisles of the supermarket this morning, but I will have forgotten it by tomorrow.
With long term memory, it seems subjectively that as memories fade with time or decreasing significance, their “resolution” decreases. That would presumably correspond to a reduction in the number of bits.
I don’t know what happens when the hunan brain brain reaches its memory limits, but it’s probably similar to the szechuan brain.
(you might want to have a mod fix the thread title)
The limitation on memory is not so much one of capacity (nor does it function like computer memory—if you don’t believe me, I dare you to memorize the order of a couple of decks of cards shuffled together, or a mere hundred thousand digits of pi, much less a couple of petabytes), but one of accessing and correlating all the contents, thus the utility of mnemonic techniques.
If you want to know what kind of sci-fi stuff we could do to future humans, that is a bit out of the scope of factual questions.
It seems to me that biological evolution of the brain memory system may not have kept cadence with how our brains increase our lifespan. And maybe even our required ability to acquire new information. and discard useless information.
Consider an AI system that has limited memory. It has the programming to take in and utilize information. The program likely has the ability to keep on taking in information, but has an ever dwindling repository to store the useful results. But it needs to use a lot of the results in order to process new information.
Seems to me it will return less reliable results with each iteration of processing new information against a lesser amount of remembered information. The information in memory may become skewed in strange ways as it is rewritten with new results. No unlimited data base with which to compare/parse new information.
Seems obvious that the human brain is nowhere close to enough for one human lifetime, even accounting for the fact that we remember almost none of our experiences. The ability to learn new things goes way down with age already.
Fortunately, we can already offload a large amount of storage to electronic devices. Phones are effectively a cybernetic memory device already. Eventually we’ll take a few steps closer to actual implanted memory devices.
This is me, some times, but I’m not blond.
Goddammit, I was going to try to find that episode.
Nobody really knows how the brain works. Even the OP’s link says “The brain’s exact storage capacity for memories is difficult to calculate. First, we do not know how to measure the size of a memory. Second, certain memories involve more details and thus take up more space; other memories are forgotten and thus free up space. Additionally, some information is just not worth remembering in the first place.”
We need to get past this modern delusion that lifespans are just going to greatly increase. That’s probably as real a possibility as everybody getting personal rocket packs. Biologic immortality is essentially meaningless.
The human brain is a fantastic marvel, way above our current understanding. Maybe the only thing we can confidently say about the brain is that no single representative of humanity comes close to making full use of all the capabilities it has.
Might as well ask what happens when we use up the galaxy.
Is this concurrent thread a coincidence?
Crossposting from the other thread…
Nope. I was inspired by this thread, and the “Married…With Children” clip in particular. 
As for human lifespan increasing “rabidly” - In the US, life expectancy at birth has gone up by a whole nine years in the last 6 decades:
Life expectancy is not lifespan. Life expectancy has gone up because of nutrition, public hygiene, treatment of chronic illnesses and the reduction in habits that result in premature death (e.g. smoking), and of course a reduction in infant mortality. Human lifespan, on the other hand, has remained fixed at about 120 years. Even improvements in medical treatment and lifestyle changes to improve health and mobility into late adulthood have not prevented the eventual senescence, and the brain appears to have a genetic clock that precisely drives cognitive development and degradation.
Stranger
If we become biologically immortal without any upgrade to our memory (and assuming the immortality includes the brain continuing to work in the same way indefinitely), we forget stuff. Eventually, we forget so much stuff, and have remembered and learned so much different stuff, including behaviours and habits, that we’re a different person that happens to live in the same body.
That is, we would appear to be a different person if two snapshots, hundreds of years apart, were compared - but to the individual experiencing the process, it’s continuous gradual change.
Even back in the time of King David, “the span of man is threescore years and ten, or fourscore if he be strong”. In other words, back then, if you managed to avoid all of the diseases and wars and other causes of premature death, you could expect to probably live to maybe 70 or 80 before dying of old age. Which isn’t too different from now. The two key differences are that, first, we’ve gotten a lot better at avoiding those premature causes of death, and second, we’ve managed to extend quality of life considerably.
Do We Have Any Idea What Might Happen When The Human Brain Reaches Its “Memory Limit?”
This shows up in your field of vision
As others have mentioned we haven’t found any reliable way to increase biological lifespan. There is certainly research going on, we are getting a better understanding of what causes senescence and there are ideas to try and approach senescence as a disease to be ameliorated. But none of them have, as of yet, produced any near-term reliable way to halt or arrest senescence. That being said, some sort of biological immortality while science-fiction, is not science fantasy, it isn’t entirely implausible some era of human could figure it out.
However, I think it is often exaggerated how much biological immortality would increase the age at which the “oldest person” lived. Remember, fixing aging just stops you from getting old. The aging process certainly takes a toll on our bodies and makes any number of types of death much more likely, but the contra isn’t necessarily true. Just because you don’t age doesn’t mean you can’t develop an unexpected aneurysm and die from it, or have a sudden heart attack, or stroke, blood clot break loose and kill you etc etc. It doesn’t mean you can’t get sick from a bad virus and die from it. On top of that there are all the “non-natural” causes of death: accidental deaths, drug overdose, homicide, suicide etc.
Maybe if you were biologically immortal, and possessed of a paralyzing fear of death and a strong desire to live as long as possible no matter what, and had vast wealth, such that you kept yourself in a bubble with round the clock emergency medical staff nearby in case anything unexpected developed, you could push 500 years or something. I question the value of that life or the quality of it, though. Living exposes you to dying, and I’m not sure there will ever be an easy way around that even if we do solve aging.
The TLDR being–even with biological mortality I wouldn’t expect the typical person to live a crazy long time, certainly average age of death would go up a good bit, but I assume memory would adjust like it does now–you don’t remember things that you don’t consider important or worth remembering.
(bolding mine)
That covers it right there. For whatever reason when you run out of memory you will forget stuff. Everybody hits that limit very early in life, we’ve all forgotten far more than we remember. Our capacity grows as we get older, but it never catches up to the amount of information that floods our heads every day.
Eh, it’d still be finite, but it’d be a lot longer. Based on Social Security stats, a 30-year-old has about a 0.18% chance of dying within a year. If we assume that “curing aging” means setting someone back to that level, then you’d see an average lifespan of around 557, with some lucky folks living many times that long. And that’s just from living like a normal present-day 30-year-old: For someone who chose to “live in a bubble”, it’d be far longer yet.