The one that always come to mind is: how will we spare space for the youths?
I’m unusually chill when it comes to population, both over and under. I’m not enormously concerned by how many people there are, I’m more concerned by how healthy the existing people are, and how healthy the environment is, both of which are mostly orthogonal to population and depend primarily on technological development. It’s important to note that fertility rates are generally declining worldwide, seemingly in tandem with economic development. The most economically developed countries generally have below-replacement fertility rates, and are facing depopulation plus highly inverted population pyramids (high ratio of sick, dependent, aged people) if something doesn’t change. In places where fertility is below two children per woman, you could abolish death completely and population will plateau, since each generation produces fewer children than the one before, so you get a geometric series with r < 1. Thus, the only study I’m aware of that analyses the demographic consequences of rejuvenation therapies predicts only slow and limited population growth (at least in Sweden).
Of course, it all depends how fertility changes. Ending reproductive senescence could allow people to postpone childbirth even further than they already do, lowering fertility rates further, or it could lead to people having more children throughout their greatly extended lifetimes. I suspect the former will occur, but time will tell.
the biologist in me is very confident that it’s terribly misleading to think biological ageing as a simple accumulation of damages
Oh, I hope I didn’t give the impression that this was simple. One of my core points is that ageing cannot be reduced to any single target for intervention, there is no way around the fact that ageing is many-faceted and will require complex combination therapies to address. I only assert that there will be some combination of damage which, if eliminated, will elicit healthy life extension, and that we have some well educated guesses as to what those are and how to go about fixing them, and that doing so can only be good for people even if damage identified by SENS platform is not in fact comprehensive.
Counter-counter-points:
Yes, cancer is hard and I glossed over it. Partly it will be mitigated by immune system rejuvenation, since immune surveillance plays a huge role in cancer suppression. Dealing with mitochondrial dysfunction should also reduce cancer incidence, by lowing the amount of free-radical assault on DNA. Aside from that though, there are exciting things happening in actual cancer therapy: cancer immunotherapy (works very well in blood cancers, might scale to solid cancers), THIO by MAIA Biotechnology (rapidly kills cells that express high levels of telomerase, which most cancers do by necessity), Lou Hawthorne’s NaNots (can safely remove stuff from the blood, can be used to soak up the soluble immune system inhibitors that tumours have to use to protect themselves from the immune system, and finally, Michael Levin’s lab have managed to suppress cancers using ion channel drugs, along with opening a whole new perspective on what cancer fundamentally is.
The effects rejuvenating effects of parabiosis are due to either good things in the young blood, or dilution / removal of bad things (e.g. inflammatory signalling molecules) in the old blood. The debate continues, but I believe consensus is leaning towards the latter, since you can achieve similar results just by diluting the blood with saline-albumin [1,2].
Function follows form. If there are diseases that aren’t associated with any obvious damage, then that only means we’ve yet to identify what the damage is. Machines do what they do because their structure; if they malfunction, then there must some change somewhere in the structure that causes it, and whatever that change is, we call it damage. Remember that damage is defined very broadly, it doesn’t have to be what you’d think of as “wear-and-tear” necessarily—it could be something like over-sensitisation of a particular type of neuron in the case of CRPS, for example.
Progeria (assuming you mean Hutchinson-Gilford syndrome) is a mutation in a critical nuclear envelope protein which causes rapid and widespread damage of many forms, since it’s such a critical component that’s defective. It’s thought of as “premature ageing” since its symptoms resemble accelerated normal ageing, probably because “widespread damage of many forms” is what normal ageing is, but that doesn’t mean that the damage involved in progeria is the same as in normal ageing (though there’s probably some overlap). As for menopause, it’s kind of a moot point to me whether a change is “under genetic control” (difficult to define since everything is ultimately determined by genes anyway) or not. Thymic involution appears to be a programmed developmental change, but we still call it damage, because it causes a loss of function (inability to make new naive T-cells). We don’t much care how damage happens, only how to reverse it.
In places where fertility is below two children per woman, you could abolish death completely and population will plateau
Why would fertility per woman stay the same when childbearing lifespan is increased? It seems more likely to me that fertility per woman per year would stay the same—have a kid or two, then a few decades doing other things, then another kid or two and so on. And this leads to exponential growth (as long as fertility/woman/year > 0).
Is that really conter counter? Levin’s idea on long range communication fits well with the ideas of cancer as learning system, even better than natural selection alone. Also, the impact of diluting blood seems 100% compatible with the idea that it’s diluting an ageing marker (indeed inflammatory molecules are excellent candidates).
If there are diseases that aren’t associated with any obvious damage, then that only means we’ve yet to identify what the damage is
we still call it damage, because it causes a loss of function
These definitions are imho too forgiving.: if we define damage as loss of health, then sure « removing damage » will tautologically cause good health. If we define damage as material defects, which I think is closer to your original intent, then maladaptative memories (of the affective system in PTSD, of the pain system in CRPS, of the immune system….) can cause a loss of function without a lasting role for material damages (beside killing oneself when it’s no longer possible to cope with this level of pain|suffering)
If we define damage as material defects, which I think is closer to your original intent, then maladaptative memories (of the affective system in PTSD, of the pain system in CRPS, of the immune system….) can cause a loss of function without a lasting role for material damages
“Material”? I don’t think it’s useful to distinguish between material and immaterial change, the point is that the change is maladaptive. If your hard drive gets corrupted preventing your computer from booting then we still call that damage, even though it seems less material than, say, shooting the PSU. And ultimately, data and code are material anyway, whether they’re represented by patterns of magnetic polarisation or changes to neuronal sensitivity or connectivity or whatever.
I’m unusually chill when it comes to population, both over and under. I’m not enormously concerned by how many people there are, I’m more concerned by how healthy the existing people are, and how healthy the environment is, both of which are mostly orthogonal to population and depend primarily on technological development. It’s important to note that fertility rates are generally declining worldwide, seemingly in tandem with economic development. The most economically developed countries generally have below-replacement fertility rates, and are facing depopulation plus highly inverted population pyramids (high ratio of sick, dependent, aged people) if something doesn’t change. In places where fertility is below two children per woman, you could abolish death completely and population will plateau, since each generation produces fewer children than the one before, so you get a geometric series with r < 1. Thus, the only study I’m aware of that analyses the demographic consequences of rejuvenation therapies predicts only slow and limited population growth (at least in Sweden).
Of course, it all depends how fertility changes. Ending reproductive senescence could allow people to postpone childbirth even further than they already do, lowering fertility rates further, or it could lead to people having more children throughout their greatly extended lifetimes. I suspect the former will occur, but time will tell.
Oh, I hope I didn’t give the impression that this was simple. One of my core points is that ageing cannot be reduced to any single target for intervention, there is no way around the fact that ageing is many-faceted and will require complex combination therapies to address. I only assert that there will be some combination of damage which, if eliminated, will elicit healthy life extension, and that we have some well educated guesses as to what those are and how to go about fixing them, and that doing so can only be good for people even if damage identified by SENS platform is not in fact comprehensive.
Counter-counter-points:
Yes, cancer is hard and I glossed over it. Partly it will be mitigated by immune system rejuvenation, since immune surveillance plays a huge role in cancer suppression. Dealing with mitochondrial dysfunction should also reduce cancer incidence, by lowing the amount of free-radical assault on DNA. Aside from that though, there are exciting things happening in actual cancer therapy: cancer immunotherapy (works very well in blood cancers, might scale to solid cancers), THIO by MAIA Biotechnology (rapidly kills cells that express high levels of telomerase, which most cancers do by necessity), Lou Hawthorne’s NaNots (can safely remove stuff from the blood, can be used to soak up the soluble immune system inhibitors that tumours have to use to protect themselves from the immune system, and finally, Michael Levin’s lab have managed to suppress cancers using ion channel drugs, along with opening a whole new perspective on what cancer fundamentally is.
The effects rejuvenating effects of parabiosis are due to either good things in the young blood, or dilution / removal of bad things (e.g. inflammatory signalling molecules) in the old blood. The debate continues, but I believe consensus is leaning towards the latter, since you can achieve similar results just by diluting the blood with saline-albumin [1,2].
Function follows form. If there are diseases that aren’t associated with any obvious damage, then that only means we’ve yet to identify what the damage is. Machines do what they do because their structure; if they malfunction, then there must some change somewhere in the structure that causes it, and whatever that change is, we call it damage. Remember that damage is defined very broadly, it doesn’t have to be what you’d think of as “wear-and-tear” necessarily—it could be something like over-sensitisation of a particular type of neuron in the case of CRPS, for example.
Progeria (assuming you mean Hutchinson-Gilford syndrome) is a mutation in a critical nuclear envelope protein which causes rapid and widespread damage of many forms, since it’s such a critical component that’s defective. It’s thought of as “premature ageing” since its symptoms resemble accelerated normal ageing, probably because “widespread damage of many forms” is what normal ageing is, but that doesn’t mean that the damage involved in progeria is the same as in normal ageing (though there’s probably some overlap). As for menopause, it’s kind of a moot point to me whether a change is “under genetic control” (difficult to define since everything is ultimately determined by genes anyway) or not. Thymic involution appears to be a programmed developmental change, but we still call it damage, because it causes a loss of function (inability to make new naive T-cells). We don’t much care how damage happens, only how to reverse it.
Why would fertility per woman stay the same when childbearing lifespan is increased? It seems more likely to me that fertility per woman per year would stay the same—have a kid or two, then a few decades doing other things, then another kid or two and so on. And this leads to exponential growth (as long as fertility/woman/year > 0).
Is that really conter counter? Levin’s idea on long range communication fits well with the ideas of cancer as learning system, even better than natural selection alone. Also, the impact of diluting blood seems 100% compatible with the idea that it’s diluting an ageing marker (indeed inflammatory molecules are excellent candidates).
These definitions are imho too forgiving.: if we define damage as loss of health, then sure « removing damage » will tautologically cause good health. If we define damage as material defects, which I think is closer to your original intent, then maladaptative memories (of the affective system in PTSD, of the pain system in CRPS, of the immune system….) can cause a loss of function without a lasting role for material damages (beside killing oneself when it’s no longer possible to cope with this level of pain|suffering)
“Material”? I don’t think it’s useful to distinguish between material and immaterial change, the point is that the change is maladaptive. If your hard drive gets corrupted preventing your computer from booting then we still call that damage, even though it seems less material than, say, shooting the PSU. And ultimately, data and code are material anyway, whether they’re represented by patterns of magnetic polarisation or changes to neuronal sensitivity or connectivity or whatever.