Neil deGrasse Tyson on Cryonics
Question:
What are your thoughts on cryogenic preservation and the idea of medically treating aging?
His response:
A marvelous way to just convince people to give you money. Offer to freeze them for later. I'd have more confidence if we had previously managed to pull this off with other mammals. Until then I see it as a waste of money. I'd rather enjoy the money, and then be buried, offering my body back to the flora and fauna of which I have dined my whole life.
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Comments (105)
The view of cryonics Tyson expresses here is, unfortunately, just the standard high-status-scientist conventional wisdom at the moment.
On the other hand, this is interesting:
In other words, he considers his greatest scientific achievement to be an improved estimate for a particular quantity, based on an analysis of biases in other people's data. That's rather...LWish.
It looks like he's just another smart guy who's no wiser outside the laboratory, which is very disappointing, as I greatly admire him as a scientist and advocate of science education. Bah. He's still on our side, or at least a fellow traveler.
(!) But look what he says here (emphasis added):
It seems this belief of his just hasn't yet propagated to the part of his mind that answers the cryonics question.
Well.. It doesn't necessarily lead to that. You can just not have children.
And it doesn't have to be not to have children at all. Ie. 1 child for everyone happens to be 0.5 children per person.
Just saying that the "space program" probably isn't the best solution.. for now.
That's quite a leap to go from "he disagrees with me on one issue" to "[he's] no wiser outside the laboratory [than an average person]."
From his reply I suspect that cryonics is something he hasn't thought about very much, whereas he has thought quite a lot about other important (arguably more important) issues. For a celebrity scientist, I am actually quite surprised how insightful and independent his thinking is on a wide range of topics.
Cryonics is very expensive, and I would guess there's only about a 1% chance of it working as currently performed. Seeing it as a potentially rare and worthwhile opportunity, or as a waste of money both seem like reasonable positions depending on a persons values and finances to me...
What are the numbers that lead to your 1% estimate?
I will eventually sit down and make a back of the envelope calculation on this, but my current off-the-cuff estimate is about twenty (yes, twenty) orders of magnitude lower.
I see. So if you made a billion trillion independent statements of the form "cryonics won't work", on topics you were equally sure about, you'd be pretty confident you were right on all of them?
? No.
I fully admitted that I have only an off-the-cuff estimation (i.e. something I'm not very certain about).
Then I asked you if you have something better - some estimate based in reality?
OK, so you have some assumptions that you attach some high but not extreme amount of probability to, according to which the chances of cryonics working are on the rough order of 10^-22. Fair enough. But given that the relevant question is how certain you are about the assumptions, why even bring up the 20 orders of magnitude, if it doesn't matter whether it's 20 orders of magnitude or 1000 orders of magnitude? What role could the 20 orders of magnitude number play in anyone's decision making?
Note that I'm a different person than user:CasioTheSane.
Ok, now we are squeezing a comment way too far. Let me give you a fuller view: I am a neuroscientist, and I specialize in the biochemistry/biophysics of the synapse (and interactions with ER and mitochondria there). I also work on membranes and the effect on lipid composition in the opposing leaflets for all the organelles involved.
Looking at what happens during cryonics, I do not see any physically possible way this damage could ever be repaired. Reading the structure and "downloading it" is impossible, since many aspects of synaptic strength and connectivity are irretrievably lost as soon as the synaptic membrane gets distorted. You can't simply replace unfolded proteins, since their relative position and concentration (and modification, and current status in several different signalling pathways) determines what happens to the signals that go through that synapse; you would have to replace them manually, which is a) impossible to do without destroying surrounding membrane, and b) would take thousands of years at best, even if you assume maximally efficient robots doing it (during which period molecular drift would undo the previous work).
Etc, etc. I can't even begin to cover complications I see as soon as I look at what's happening here. I'm all for life extension, I just don't think cryonics is a viable way to accomplish it.
Instead of writing a series of posts in which I explain this in detail, I asked a quick side question, wondering whether there is some research into this I'm unaware of.
Does this clarify things a bit?
Fascinating. I've been waiting for a while for a well-educated neuroscientist to come here, as I think there are a lot of interesting questions that hinge on issues in neuroscience that are at least hard for me to answer (my only exposure to it is a semester-long class in undergrad). In particular, I'd be interested to know what level of resolution you think would be necessary to simulate a brain to actually get reasonable whole-brain emulations (for instance, is neuronal population level enough? Or do we need to look at individual neurons? Or even further, to look at local ion channel density on the membrane?)
Local ion channel density (i.e. active zones), plus the modification status of all those ion channels, plus the signalling status of all the presynaptic and postsynaptic modifiers (including NO and endocannabinoids).
You see, knowing the strength of all synapses for a particular neuron won't tell you how that neuron will react to inputs. You also need temporal resolution: when a signal hits the synapse #3489, what will be the exact state of that synapse? The state determines how and when the signal will be passed on. And when the potential from that input goes down the dendritic tree and passes by the synapse #9871, which is receiving an input at that precise moment - well, how is it going to affect synapse #9871, and what is the state of synaps #9871 at that precise moment?
Depending on the answer to this question, stimulation of #3498 followed very soon after with stimulation of #9871 might produce an action potential - or it might not. And this is still oversimplifying things, but I hope you get the general idea.
If you have a technical argument against cryonics, please write it up as an actual blog post, ideally under your real name so you can flash your credentials. It will be the most substantial essay arguing for such a point ever written: see my blog. I'm pretty convinced that if there was really a strong argument of the sort you're trying to make, someone would already have done this, so I take it as strong evidence that they haven't.
This was supposed to be a quick side-comment. I have now promised to eventually write a longer text on the subject, and I will do so - after the current "bundle" of texts I'm writing is finished. Be patient - it may be a year or so. I am not prepared to discuss it at the level approaching a scientific paper; not yet.
Keep in mind two things. I am in favor of life extension, and I do not want to discourage cryonic research (we never know what's possible, and research should go on).
Not weighing in either way on cryonics itself, but on the meta level: Why do you consider that strong evidence? It seems to me that most people who don't think cryonics will work simply aren't interested in it, and therefore haven't tried very hard to prove that they're right.
No doubt you can identify particular local info that is causally effective in changing local states, and that is lost or destroyed in cryonics. The key question is the redundancy of this info with other info elsewhere. If there is lots of redundancy, then we only need one place where it is held to be preserved. Your comments here have not spoken to this key issue.
The brain has redundancy at the level of neurons: it is quite resilient against diffuse neuron loss, and in case of localized damage, unless the affected area is large or includes key regions such as the brainstem, impairment is often limited to one or a few functions, and in some cases it even reorganizes to transfer the lost functions to other areas, partially recovering them.
However, there is no expectation that the brain has redundancy against the loss of an information storage medium that is used in all neurons.
If you destroy half of your collection of DVDs, the information in the other half is still intact. If you destroy every odd-numbered track on all of your DVDs, instead, most of the remaining data will be too fragmentary to be of any use, even if the number of bits you destroyed is the same in both cases.
I will quickly remark that some aspects of this comment seem to betray a non-info-theoretic point of view. From the perspective of someone like me, the key question for cryonics are "Do two functionally different start states (two different people) map onto theoretically indistinguishable molecular end states?" You are not an expert on the future possibilities of molecular nanotechnology and will not be asked to testify as such, but of course we all accept that arbitrarily great physical power cannot reconstruct a canister of ash because the cremation process maps many different possible starting people to widely overlapping possible canisters of ash. It is this question of many-to-one mapping alone on which we are interested in your expertise, and I would ask you to please presume for the sake of discussion that the end states of interest will be distinguished to molecular granularity (albeit obviously not to a finer position than thermal noise, let alone quantum uncertainty).
That said, I think we will all be interested if you can expand on
and whether you mean this in the customary sense of "it won't boot back up when you switch it on" or in the info-theoretic sense of "this process will map functionally different synapses to exactly similar molecular states, or a spread of such states, up to thermal noise". You are not being asked to overcome a burden of infinite proof either - heuristic argument is fine, we're not asking for particular proofs you can't possibly provide - we just want to make sure that what is being argued is the precise question we are interested in, that of many-to-one mappings onto molecular end states up to thermal noise.
EDIT: Oops, didn't realize this was an old comment.
Shake your head. Vigorously. (Do it.)
There, I've just caused you to scramble a vast array of concentration gradients, proteins tumbling around in a merry free-for-all. I have thus killed the old king, vive le roi nouveau!
If that's not enough, consider the forces inertia exerts on all those precious gradients and precise molecule orientations when on a rollercoaster. Uh oh.
The molecular states may not have to be exactly similar after all to yield functional equivalency within an acceptable margin, a margin we deem acceptable throughout our lives. Let's not worry about a few non-injective transformations?
I was initially swayed by Kalla724's arguments (as well as a little molecular biology background), but it's missing the forest for the trees.
Do you think uploading C. elegans is impossible?
In general, uploading a C. elegans, i.e. creating an abstract artificial worm? Entirely doable. Will probably be done in not-too-distant future.
Uploading a particular C. elegans, so that the simulation reflects learning and experiences of that particular animal? Orders of magnitude more difficult. Might be possible, if we have really good technology and are looking at the living animal.
Uploading a frozen C. elegans, using current technology? Again, you might be able to create an abstract worm, with all the instinctive behaviors, and maybe a few particularly strong learned ones. But any fine detail is irretrievably lost. You lose the specific "personality" of the specific worm you are trying to upload.
I'm reading your comment and am now thinking of this as startlingly optimistic, particularly this bit, which appears just wrong per your comment. Except I realise I don't understand the area enough to rewrite that bit. Gah. Are the Wikipedia articles on what you're talking about here any good for getting up to speed?
The point you're making seems to be that performing the repair is impossible in practice. Apart from that difficulty, do you think enough information is preserved in the location of all atoms in a cryopreserved brain, so that given detailed knowledge of how brains work in general this information would in theory be sufficient to reconstruct the initial person (even if this information is impractical to actually extract or process)? One possibility for avoiding the reconstruction of brains out of atoms is to instead reconstruct a Whole Brain Emulation of the original person. Do you think developing the technology of WBE is similarly impossible, or that there are analogous difficulties with use of WBE for this purpose?
I don't believe so. Distortion of the membranes and replacement of solvent irretrievably destroys information that I believe to be essential to the structure of the mind. I don't think that would ever be readable into anything but a pale copy of the original person, no matter what kind of technological advance occurs (information simply isn't there to be read, regardless of how advanced the reader may be).
Can you elaborate on the damage that is occurring, even with cryoprotectants?
Why/how would low temps in a cryoprotectant denature proteins?
If you have time I would really like to see the detailed posts, perhaps even in a new thread. I am also a bioengineer/biophysicist but I have little knowledge of neuroscience.
I'll eventually organize my thoughts in something worthy of a post. Until then, this has already gone into way more detail than I intended. Thus, briefly:
The damage that is occurring - distortion of membranes, denaturation of proteins (very likely), disruption of signalling pathways. Just changing the exact localization of Ca microdomains within a synapse can wreak havoc, replacing the liquid completely? Not going to work.
I don't necessarily think that low temps have anything to do with denaturation. Replacing the solvent, however, would do it almost unavoidably (adding the cryoprotectant might not, but removing it during rehydration will). With membrane-bound proteins you also have the issue of asymmetry. Proteins will seem fine in a symmetric membrane, but more and more data shows that many don't really work properly; there is a reason why cells keep phosphatydilserine and PIPs predominantly on the inner leaflet.
You'll need to read Molecular Repair of the Brain. Note that it discusses a variety of repair methods, including methods which carry out repairs at sufficiently low temperatures (between 4K and 77K) that there is no risk that "molecular drift" would undo previous work. By making incredibly conservative assumptions about the speed of operations, it is possible to stretch out the time required to repair a system the size of the human brain to three years, but really this time was chosen for psychological reasons. Repairing a person "too quickly" seems to annoy people.
You might also want to read Convergent Assembly. As this is a technical paper which makes no mention of controversial topics, it provides more realistic estimates of manufacturing times. Total manufacturing time for rigid objects such as a human brain at (say) 20K are likely to be 100 to 1000 seconds. This does not include the time required to analyze your cryopreserved brain and determine the healthy state, which is likely to be significantly longer. Note that some alterations to the healthy state (the blueprints) will be required prior to manufacture, including various modifications to facilitate manufacture, the inclusion of heating elements for rewarming, and various control systems to monitor and modulate the rewarming and metabolic start-up processes as well as the resumption of consciousness.
After you've had time to digest the paper, I'd be interested in your comments. As Ciphergoth has said, there are no (repeat no) credible arguments against the feasibility of cryonics in the extant literature. If you have any, it would be most interesting.
As a neuroscientist, you might also be amused by Large Scale Analysis of Neural Structures.
For recent work on vitrification, I refer you to Greg Fahy at 21st Century Medicine.
Mine was also just an off-the-cuff "guesstimate."
I am skeptical that it is possible to estimate the chances of cryonics working in a rigorous quantitative way. There's no way to know what technical hurdles are actually involved to make it work. How can you estimate your chances of success when you have no information about the difficulty of the problem?
Um...there is quite a bit of information. For instance, one major hurdle was ice crystal formation, which has been overcome - but at the price of toxicity (currently unspecified, but - in my moderately informed guesstimate - likely to be related to protein misfolding and membrane distortion).
We also have quite a bit of knowledge of synaptic structure and physiology. I can make a pretty good guess at some of the problems. There are likely many others (many more problems that I cannot predict), but the ones I can are pretty daunting.
I was unclear, I didn't mean that there's no information, just that there's potentially no information on specific areas that are critical for a meaningful prediction:
Given that both of these types of events are common when developing new technology, attempting to predict how long it will take and how well it will work is basically a waste of time. Even if you synthesize all of the data you have in a rigorous way and come up with a number, I expect that the number would have error bars so large that it's merely a quantitative expression of the impossibility of accurately predicting such events with the data you have.
I am curious about what are the biggest obstacles you see that cause you to give 20 order of magnitude lower an estimate than I do. If that is accurate, thinking about and working on cryonics is a pointless waste of time.
I agree with you on both points. And also about the error bars - I don't think I can "prove" cryonics to be pointless.
But one has to make decisions based on something. I would rather build a school in Africa than have my body frozen (even though, to reiterate, I'm all for living longer, and I do not believe that death has inherent value).
Biggest obstacles are membrane distortions, solvent replacement and signalling event interruptions. Mind is not so much written into the structure of the brain as into the structure+dynamic activity. In a sense, in order to reconstruct the mind within a frozen brain, you would have to already know what that mind looks like when it's active. Then you need molecular tools which appear impossible from the fundamental principles of physics (uncertainty principle, molecular noise, molecular drift...).
My view of cryonics is that it is akin to mercuric antibiotics of the late 19th century. Didn't really work, but they were the only game in town. So perhaps with further research, new generation of mercuric substances will be developed which will solve all the problems, right? In reality, a much better solution was discovered. I believe this is also the case with life extension - cryonics will fade away, and we'll move in with a combination of stem cell treatments, technologies to eliminate certain accumulated toxins (primarily insoluble protein aggregates and lipid peroxidation byproducts), and methods to eliminate or constrain cellular senescence (I'm actually willing to bet ~$5 that these are going to be the first treatments to hit the market).
I agree with you that the enormous cost is probably not worth it, when you start thinking what else could be accomplished with the money in the context of it's low probability of success.
However, those technologies that increase human lifespan are really something entirely different than cryonics, not a replacement for it.
Even if we increase lifespan significantly, as long as we still have a lifespan cryonics would allow us to remain frozen until even more life extension technologies come about. It's also a potentially viable method for keeping people alive for long distance space travel at sub-relativistic speeds.
I'd look forward to seeing a more detailed post (or even a journal article) from you going into the biochemistry specifics of the problems with cryonics you mention in this post, and your other posts in this thread. I am particularly curious why rehydration would denature proteins which are naturally stable in water? And what sort of membrane distortions would occur that aren't reversible?
All good reason to keep working on it.
The questions you ask are very complex. The short answers (and then I'm really leaving the question at that point until a longer article is ready):
I said that because it seemed he was giving the pat, standard, "I haven't thought about this" answer. I don't know if Tyson is sloppy in all thinking outside the lab, but he seemed to be sloppy here. I wouldn't mind if he disagreed with cryonics after having examined the issue in detail, but he's giving an answer (seemingly) without having thought about it very much.
In short, I think I mostly agree with you.
Indeed. (As a non-cryonicist myself, I might well feel offended.)
(Nitpick: Cryogenics is the study of producing near absolute zero temperatures. You mean "cryonics".)
Thank you. Title updated.
The best way to convince people to give you money is to offer them something of exceptionally high value.
It's perverse logic to imply that a service has lower value because people are willing to pay for the service.
Tragically, the extremely small number of people who have signed up for cryonics proves it's not a "marvelous way" to "convince people to give you money."
I think the fixed version of the statement is that the persuasiveness-to-actual-value ratio is high, so even if persuasiveness is low, that just translates to the actual value being lower still.
That's a lovely bit of rhetoric to appeal to the Greens. (I say rhetoric because if you are cremated, there's nothing to offer back, and if you are buried, you are usually embalmed and now 'the flora and fauna' will be poisoned if they try to take your offer anytime soon.) I wish I could manage that trick.
All the biological material will be cycled back into the ecosystem, most of it quite soon - even despite the presence of toxins (formaldehyde-eating bacteria, etc). His statement is correct in the sense that if you are cryopreserved, the net amount of carbon, nitrogen, phosphorus, etc in the biosphere will be slightly lower than it otherwise would have been.
Not attacking your position, just pointing that out.
"I'd have more confidence if we had previously managed to pull this off with other mammals."
Some mammals are pretty good at doing it themselves... http://users.iab.uaf.edu/~brian_barnes/publications/1989barnes.pdf
You could say that billions of dollars spent on cancer research is a huge waste of money because curing cancer has not been proven to work in small mammals. There is no proof that cancer can be cured. I am not being entirely sarcastic about this, but I would give a higher probability for success to most of the Strategies for Engineered Negligible Senescence to achieve rejuvenation. Knowledge of the forms of damage that result in aging is the first step toward repairing that damage. With cryonics the problem is similar: there is damage to be repaired, and it is not unreasonable to believe that in 50 or 100 years the molecular repair technology will be available. It would be foolish to believe that humans will never be able to live on Mars until you see humans living on Mars. The ability to extrapolate from present technology to future technology requires more sophistication than simplistic empiricism.
If what you say were true - we "never cured cancer in small mammals" - then yes, the conclusion that cancer research is bullshit would have some merit.
But since we did cure a variety of cancers in small mammals, and since we are constantly (if slowly) improving both length of survival and cure rates in humans, the comparison does not stand.
(Also: the integration unit of human mind is not the synapse; it is an active zone, a molecular raft within a synapse. My personal view, as a molecular biophysicist turned neuroscientist, is that freezing damage is not fixable from basic principles (molecular drift over a few years is sufficient to prevent it completely). In my mind, the probability that some magical "damage repair" technique will be developed is within the same order of magnitude with probability that Rapture will occur. Cryonics is important primarily in the sense that it provides impetus for further research; but a radically different method of preservation is required before possibility of revivification reaches any reasonable level.)
I'm not quite sure what you mean by molecular raft, but do you think you need to record properties of molecular rafts or just properties of the population of molecular rafts in the neuron? (e.g. amount of each type)
Perhaps a better definition would help: I'm thinking about active zones within a synapse. You may have one "synapse" which has two or more active zones of differing sizes (the classic model, Drosophila NMJ, has many active zones within a synapse). The unit of integration (the unit you need to understand) is not always the synapse, but is often the active zone itself.
I might as well post this here because I don't think it's worth a new thread. Let's assume for the purposes of this argument that you have a suitably high confidence in cryonic revival at some future time. How much do you weigh the number of deaths as a direct consequence of electricity consumed keeping you frozen, against your irreplaceablity in the future society? I'm assuming that there is a non-trivial amount of electricity involved, and substituting the monetary costs of electricity per Folding@Home user per year, with the amount paid per person per year to purchase cryonics services.
Does this train of thought hold at all? If anyone has the time and knowledge to run some numbers, that would be great...
Cryonics storage doesn't consume even a visible fraction of industrially produced liquid nitrogen. And it won't for ten-thousands of patients to come.
Retracted after a bit of research; they just add more liquid nitrogen to counteract evaporation, and don't actually use any electricity. (I honestly didn't know this.)
Anyone who knows what these two picturse are and where they come from? Nemesis is doing some I think not very accurate critique of LessWrong on the Swedish Skeptics internet forum. It is in Swedish, and sorry, I have not time to translate into English. But though I do not know, I suspect that Nemesis have not produced them by himself but found them somewhere. If anyone knows I would be glad to know. (If someone should know already and recogises them, I do not ask anyone to spend significant time on it.)