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Our closest worm kin regrow body parts, raising hopes of regeneration in humans
- PeterisP 10y agoWell, a plausible answer is that if we (or random mutations) re-enable those genes then the end result is simply a lot of cancer. A reasonable default assumption is that each switch in our "genetic configuration" is set to a quite good value. The only exception is if we see a feature that is beneficial at a high calorie cost - those features have been (reasonably) optimized away during our evolution, but would be useful in modern circumstances where food is not scarce anymore; this is a tradeoff where it would make sense to just turn the dial way to the right from where it had been throughout the last million years.
- ryandvm 10y agoThe ability to regenerate body parts and cancer are not inextricably linked. Take the axolotl. It has the ability to regenerate entire limbs. It's also estimated to be a couple orders of magnitude more resistant to cancer than humans.
- mattnewton 10y agoMaybe that's the ticket? The cancer resistance is something that allows the axolotl to also keep regrowing limbs around in the genome?
- dharma1 10y agoThere are also many animals who are long living, and immune to cancer (to varying degrees). Naked mole rats live up to 30 years and almost never get cancer (only one case formally verified so far). Elephants have many more cells than us, and live to almost the same age, but only have a 5% chance of getting cancer, vs 10%-25% in humans. Lions have a 2% chance of getting cancer.
- lordnacho 10y agoOut of curiosity, how do we know the cancer rates of various animals? Someone would have had to examine a lot dead animals of various species to figure this out.
- trentmb 10y ago> Take the axolotl. It has the ability to regenerate entire limbs. It's also estimated to be a couple orders of magnitude more resistant to cancer than humans. The lifespan of of the axolotl is 10-15 years. I'd love to see the cancer rates for 71 year old axolotls.
- meric 10y agoAnd perhaps some people might risk the chance of cancer to grow their body parts back.
- mparlane 10y agoAlso with regeneration just cut out large chunks containing cancer and hope round 2 of your lungs is better!
- Grishnakh 10y agoPerhaps it could be turned on and off as needed: lose a finger in an accident, and take a drug to turn regeneration on. Grow your finger back in a week, and then take another drug (or stop taking the first drug) to go back to normal.
- mparlane 10y agoYour comment was either flagged or downvoted in to oblivion... I have vouched for it as I can't see any reason for either...
- PeterisP 10y agoThat's not how it works. For your finger to be capable of regeneration, the relevant genes would have to be in all your cells beforehand. Advanced genetic engineering can be used to ensure that particular genes get activated only in the presence of some molecule that isn't naturally present in humans, so it would happen only if you take that particular drug; but it would still be applicable only to "newly built" humans e.g. as part of in vitro fertilization, not as something that can be applied to adults.
- Grishnakh 10y agoWhy couldn't CRISPR or some more-advanced technique not yet discovered be used to insert the relevant genes into your cells? (Obviously, IANAG (geneticist))
- awqrre 10y agoif you got cancer, just cut that piece off and eat more?
- Ygg2 10y agoYeah, just regrow that brain, liver, thyroid gland. It could be those genes raise chance of cancer everywhere. Not just limbs.
- awqrre 10y agoI'd be willing to activate that feature if I was about to die.
- Ygg2 10y agoIdea was not to activate ability. But to be born with it.
- flukus 10y agoAre there animals that regrow their brain after a partial labotomy? In any case, humans can live with large chunk of brain removed, under the right circumstances.
- bradyd 10y agoThe liver can regenerate. As little of 25% of the original liver mass can regenerate back to full size after either surgical removal or chemical injury.[1] [1] https://en.wikipedia.org/wiki/Liver_regeneration https://en.wikipedia.org/wiki/Liver_regeneration
- SilasX 10y ago>Well, a plausible answer is that if we (or random mutations) re-enable those genes then the end result is simply a lot of cancer. Interesting idea, but does the risk of cancer have that much selective pressure? It tends to be the "last thing that kills you", after you live long enough to survive everything else. So it seems like any increased risk of cancer would have to be pretty high before it traded off against injury recovery. Then again, "injury recovery" might not have been as beneficial either -- the time to regenerate would still leave you vulnerable, so adaptations favoring avoidance of that injury would have a leg up in selective pressure.
- evilduck 10y agoCancer is probably selected against to a degree. At least for most normal healthy males, not dying prematurely of cancer means you've got probably 50 or so years to pass on your genes. If a cancer causing mutation kills you at 30, you may still have the chance to pass on your genes, but you're still being outcompeted in the larger gene pool by those who don't die early and have more children than you. And if not you, then your children who die prematurely may not procreate. Evolution doesn't really have much noticeable effect at the scale of single generations anyways.
- marcoperaza 10y agoIt's typically something that only hits you in old age because your body defends against it quite effectively.
- PeterisP 10y agoFor large animals, I'd believe that it's very rare to have non-fatal injuries that are large enough where regeneration would make a big difference to future life. According to evolution (which hasn't yet noticed medicine), if something rips off your foot, that's not an injury, you simply bleed to death or die of infection even if you win the fight - unlike, say, various small regenerating lizards. What selective pressure could there be to regenerate feet if there were almost no (alive) people with missing feet until the last few hundred years? However, risk of cancer is serious selective pressure even with short lives - e.g. https://en.wikipedia.org/wiki/Devil_facial_tumour_disease https://en.wikipedia.org/wiki/Devil_facial_tumour_disease. Cancer tends to be the "last thing that kills you" exactly because so much of our biology is tuned to resist cancer. Also, all kinds of mechanisms causing our aging problems seem to be simply evolutionary adaptations to resist cancer by limiting cell division.
- ciokan 10y agoMost likely cancer as a disease will be a solved problem before we could enable this body part regeneration thing...if ever.
- JonathonW 10y ago> A reasonable default assumption is that each switch in our "genetic configuration" is set to a quite good value. I'd question that assumption-- each switch in our "genetic configuration" is set to a value, and it's set to one that results in survival often enough for the species to reproduce, but it's not necessarily the optimal value, or even a particularly good one. It's just one that happened to be able to survive under environmental pressures at some particular time. To put this into a computer science context, genetic algorithms have the same problem-- they can find local maxima easily, but can have difficulty (depending on the nature of the search space) locating global maxima because they can't sacrifice short-term fitness to gain long-term fitness.
- trentmb 10y ago> A reasonable default assumption is that each switch in our "genetic configuration" is set to a quite good value. Least awful sounds more correct.
- BurningFrog 10y agoAnother exception would be if a limb has fallen off or otherwise failed. Then it would be great to be able to turn regeneration on, for that limb only. Any added risk should be much smaller than the always-on version.
- ThrustVectoring 10y agoThat's a bit much to expect out of evolution. First it needs a way to detect whether a limb has fallen off or otherwise failed. Then it needs to send a biochemical signal to the cells in the area iff the limb in the area failed. Then it needs to activate the regeneration iff the chemical signal is present. And each of these mutations has to be beneficial to the organism (or at least randomly there and costless). You can mush together the detection and signaling by having a local signal (like the biochemistry responsible for scabbing - iirc what happens is blood would do interesting chemistry while bleeding anyways, and so "turn into a scab when that chemistry is happening" is a worthwhile mutation), but still, it's a few too many steps.
- BurningFrog 10y agoI agree. What I was thinking (but didn't say) is that maybe we can make that happen with technology!
- anshou- 10y agoMaybe. The elephants being born without tusks due to ivory hunting pressures changing reproduction dynamics are likely at a disadvantage overall, but in the short term they will survive. Having tusks may be objectively better, but right now it'll get you killed.
- MichaelBurge 10y agoIt seems like the cells in a worm are relatively position-independent, so they can regrow using only local information. If you lopped off your leg, a cell would need to know how much of the leg to regrow to get to the kneecaps, how much to grow to get to the foot, or more. If you chopped off a foot, it seems hard to know which parts need to be regrown and which don't. There's a lot of complexity in a foot.
- cmdrfred 10y agoThis has to be a solved problem unless the womb offers some sort of telemetry.
- deleted 10y ago[deleted]
- MichaelBurge 10y agoIn that case, the entire organism is forming. It can use techniques like forming the general structure before filling in the details. It could be that forming the general structure is carefully scripted by chemistry, while the details are mostly position-independent. Bones can have their lengths determined by biological clocks that operate over years. Examples of clocks are hormone release cycles, which the rest of the body uses for signaling. But, a new leg wouldn't have access to the global clock, since it would've shut off if the affected parts are fully-developed. Bones and muscles might have their final shapes partially determined by outside forces. The biggest one is gravity. It may be that people develop longer legs in space, or their spines don't develop correctly. A leg intended to be regrown on an adult might not have time to be shaped in this manner.
- jonknee 10y agoIt's more than just worms that regenerate body parts. Some salamanders can regenerate whole limbs. https://www.youtube.com/watch?v=EsCSwVx3GvA https://www.youtube.com/watch?v=EsCSwVx3GvA
- shripadk 10y agoI remember seeing a story on BBC a while ago about how one guy, who lost the top portion of his finger while operating a toy in his hobby shop, was able to regrow it completely. It only took 4 weeks to regrow, including the nails, fingerprints et al., exactly as it was before using extracellular protein from pig bladder. Here is a link to the story: https://www.youtube.com/watch?v=NEnLK0oJCa8 https://www.youtube.com/watch?v=NEnLK0oJCa8
- traviswingo 10y agoI'm a huge believer that humans can cherry-pick the best traits of many different species and apply them to ourselves. It might sound like science fiction right now, bit give it time and we humans will have unlocked some crazy things that we claimed to be "impossible." It's always impossible until it's done. And to be honest, I think the second something is thought of, it becomes possible. I live for this shit.
- deleted 10y ago[deleted]
- partycoder 10y agoWell, it depends what you consider to be "the best". If you have watched the olympics, you can see that different body types are better suited for different sports. A basketball player playing ping pong or viceversa? probably not very successful.
- mattnumbe 10y agoBut if that basketball player had super speed and agility, then he would be good at both sports. You're only thinking about what humans are like now. If we could freely add and take away genetic mutations, who knows what kind of freaky immortal animals we'll look like in the future. We may also not care about sports at that point.
- deleted 10y ago[deleted]
- astrodust 10y agoMechanically there's an advantage to shorter limbs for particular sports, that's just how physics works. If a basketball player could be made super-human they might trounce ordinary ping-pong players, but a super-human ping-pong player would destroy them. Plus there's more to these sports than any one aspect. It's never just strength or height or stamina, it's a complex of factors. Finding that optimal even given all the options might be difficult. There's intrinsic trade-offs. For example, there's two kinds of muscle tissue, that better suited to fine motor skills and that suited to brute strength. Most animals are heavily stacked in the latter category, that's why a chimpanzee can tear you in half, but they lack the sorts of fine control that permits us to do things like type with agility and write precisely.
- mikedilger 10y agoThe processes that built us originally worked with much smaller versions of us. The techniques for constructing an arm that is a few cells wide may not work when the arm is millions of cells wide.
- agumonkey 10y agoWatching axolotl regrow a full limb is quite exciting mentally. The thing reboots topologically and not 'linearly' like most wounds. The bioengineering if I may say so seems passionating. If I could I'd go Inti embryology.
- jtchang 10y agoThis is the type of research where I like to fantasize about the outcome. As a human race we've managed to basically cheat evolution with our advances in medicine and technology. If somehow we can stay alive as a species long enough we very well might be able to discover the secret to regeneration and immortality in some way.
- jonknee 10y ago> If somehow we can stay alive as a species long enough we very well might be able to discover the secret to regeneration and immortality in some way. Hopefully we won't figure that out before we figure out how to not overcrowd Earth.
- avodonosov 10y agoForbid procreation for those who chosen immortality. If you decided to spawn children, then free space for them - die. (Or go cryopreservation and be kept in a small box occupying little space. In this case you and your decedents can live in turns: they live for one century while you sleep frozen; next century other way around).
- jonknee 10y agoYou can't let people choose because even a small percentage of people choosing immortality a generation will end up overcrowding the planet given enough time.
- avodonosov 10y agoThis depends on the reproduction rate. If it's > 1 then you're right. BTW, controlling reproduction rate is a way to not overcrowd Earth.
- JumpCrisscross 10y ago> Forbid recreation for those who chosen immortality How do you police sex in a democracy?
- woofyman 10y agoLizards can regrow their tails. https://www.google.com/amp/s/www.geneticliteracyproject.org/2016/11/11/regrowing-limbs-gene-map-of-how-lizards-regrow-tails-offers-insight-to-regenerative-medicine/amp/?client=safari https://www.google.com/amp/s/www.geneticliteracyproject.org/...
- reasonattlm 10y agoThe interesting studies are all in zebrafish and salamanders, not worms. One of the more intriguing of the recent ones is this from last year, strongly reinforcing the theory that most species lost proficient regeneration due to evolutionary battles between cancer and aging. The greater question is perhaps why there are any proficient regenerators among the vertebrates rather than why we can't do it. https://www.ucsf.edu/news/2015/11/251746/human-gene-prevents-regeneration-zebrafish https://www.ucsf.edu/news/2015/11/251746/human-gene-prevents... "Whether the regenerative powers of zebrafish and salamanders represent ancient abilities that mammals have lost, perhaps in exchange for advanced tumor-suppression systems remains an open question for biologists. Most tumor suppressor genes, being extremely useful for preventing cancer and for forming tissues during development, are broadly distributed and conserved across many different species. Recent studies, however, suggest that one, the ARF gene, arose more recently in the avian and mammalian lineage, and has no equivalent in the genomes of highly regenerative animals. To explore whether this gene might play a role in preventing tissue regeneration in humans, the researchers added human ARF to the zebrafish genome and assessed how it affected the fishes' normal ability to regrow damaged fins after injury. They found that human ARF had no effect on the fishes' normal development or response to superficial injury, but when the researchers trimmed off the tip of a fish's tail fin, the gene became strongly activated and almost completely prevented fin regrowth by activating a conserved tumor-blocking pathway."
- marvy 10y agoThat is sufficiently interesting to make me wish I could upvote it twice. But. What I really want to hear about is the opposite experiment. Take something that has ARF, and see what happens if you take it out.
- avodonosov 10y agoIt would be good to regenerate at least teeth.
- awqrre 10y agothat was my first thought as well ( I just had a bad dentist experience... )
- avodonosov 10y agoI've read of a research to grow teeth from stem cells (but I'm not sure the sources of this info were reliable)
- Turing_Machine 10y agoTeeth might also be a good area to look at in terms of figuring out how it works. Since most people already grow two full sets of teeth, and I believe there are numerous cases on record of people who have grown more than that, perhaps the regeneration genes are already partially activated in that region of the body.
- aninhumer 10y agoI'm not a dentist, but I get the impression that milk teeth and adult teeth are different things, not a regeneration cycle?
- Asooka 10y agoYep. If you're morbidly curious, you can google "baby skulls" (unsettling on so many levels, to be honest) to see how we're all born with TWO sets of teeth in our jaws. One just falls off as the ones above them push them out.
- m0llusk 10y agoRegenerating body parts doesn't happen because it is hugely expensive in terms of biochemical resources. Teeth are the most materially expensive parts of the human body. That is why teeth are often the most long lasting and best preserved human remains.
- partycoder 10y agoProbably because limb regeneration wasn't a favored trait during our evolution. e.g: we managed to survive and be fertile without it. Rather than limb regeneration we evolved pain and fear to prevent losing a limb in the first place. A similar question would be why aren't fruit toxic so animals stop eating them? Because they pass their genes anyways. Rather than that, animals that were too good at eating fruit, destroyed their own food source and died. Another interesting phenomenon are lemmings. Why lemmings kill themselves en-masse? Because they're too fertile. And as a population their own way to control their size is to mass suicide. The hawk and dove model game in game theory attempts to explain a bit of this.
- jostmey 10y agoYou are spot on correct. And regenerating lost body parts will require far more than just flipping the activation of a few genes.
- astrodust 10y agoDon't think that just because natural selection tended to favor a particular thing that it's necessarily a good thing. Some sheep have the most ridiculous horns because of how they compete for mates. If, in some alternate world, those sheep became intelligent and lived in a civilized society where such a thing was no longer relevant the horns themselves might have little worth other than prestige. They serve no functional purpose. Humans have survived in spite of our relative weaknesses. We've got a seriously screwed up head, nothing in there is oriented correctly, and parts of our body are on the verge of self-destructing even at the best of times. We were never intended by nature to live more than twenty years, everything past that is actually quite unnatural, as everything in your body starts falling apart at that point because from the perspective of natural selection taking place fifty thousand years ago you've either bred and done your duty, or you're dead weight. There's a lot of mistakes in our DNA that time will correct, but we can always jump start that process by making a few tweaks today.
- derekp7 10y agoFruit relies on being eating to assist in seed dispersal (notice how the seeds are usually cast aside?). Also, most of the fruit that you find in the supermarket are selectively bred to have quite a bit more flesh to them. Oh, and lemmings don't mass suicide. That's a myth that came about cause of Disney.
- abledon 10y agoOne answer I've read in The Spark In The Machine[1], is that our cells' organizational energies (or Qi in Chinese Medicine) is not strong enough as we grow older. Only when someone is super young (when their qi is super strong) can they regrow body parts and very small ones (the tips of the fingers!)[2] """ Doctors have seen the effect in humans without quite understanding how it happens. "Kids will actually regrow a pretty good fingertip, after amputation, if you just leave it alone," says Dr. Christopher Allan, from the University of Washington Medicine Hand Center, who wasn't involved in the research. """ EDIT: yeah i know its HN so i'll probably get downvotes, but as far as modern science is concerned we still know very little about embryology and what actually controls the beautiful orchestration of a single cell developing into a full human in 9 months. The idea of an organization energy that directs embryological cellular function is now starting to be investigated in western science [3] [1]https://www.amazon.com/Spark-Machine-Acupuncture-Explains-Mysteries/dp/1848191960 https://www.amazon.com/Spark-Machine-Acupuncture-Explains-My... [2] http://www.npr.org/sections/health-shots/2013/06/10/190385484/chopped-how-amputated-fingertips-sometimes-grow-back http://www.npr.org/sections/health-shots/2013/06/10/19038548... [3] https://vimeo.com/26761300 https://vimeo.com/26761300
- marvy 10y agoI am kind of doubtful about this Qi business. I followed the amazon link you gave and it made it even more doubtful. Nevertheless, I gave you an upvote, because I had no idea fingertips could ever regrow; that's really cool! I'm not sure what point you're trying to make with the third link. Are you saying Qi is electric?
- abledon 10y agoYes! the term "Qi" is just another way to denote the organizational electric energies our bodies use to orchestrate cellular function. This video does a way better job at describing it: https://vimeo.com/154294365 https://vimeo.com/154294365 (2 minutes)
- marvy 10y agoOkay, fine. Then what makes you say that children have more than adults?
- kazinator 10y ago"Why can't we break off half a microchip, and then rebuild the missing part so it works again? We have all the mask artwork and silicon wafers ..."
- andars 10y agoThis doesn't strike me as a reasonable analogy. 1) Microchips don't grow autonomously in the first place, unlike organisms. 2) The article's point is that not only do humans have the "mask artwork and silicon wafers", but also the genes that other organisms use to regenerate portions of their body. A closer equivalence would be "the instructions on how to rebuild the missing half of the microchip from what remains".
- kazinator 10y agoMicrochips grow autonomously if you regard the entire fab and its staff as a big organism. And note that the blueprints for the chip do actually encode more or less what it looks like: as a genotype they resemble the phenotype. Yet such a repair is not feasible. DNA genes do not encode an arm or a leg directly, but a convoluted process by which the structure develops.
- guitarbill 10y ago> Yet such a repair is not feasible. Well, we don't really know, because we've never bothered to build a chip/fab process with that capability. It's cheaper to just throw broken ones away (edit: plus, it isn't morally reprehensible to throw them away because they don't have consciousness... yet). I guess the other thing is that a CPU is pretty simplistic compared to a big organism. We do bin products and then e.g. underclock or disable parts of them accordingly. So there's the start of an "injury"-sensing mechanism. But microchips still have a few thousand years to go in their "evolution" at least :)
- rmtew 10y agoThe old UK sci-fi television series, Blakes 7, which aired in 1970's had this as one of their predicted technologies. Entire portions of machinery would regenerate after being exploded in sabotage. Grids of "radiation mine wire" would after being cut, would have the ends of the cable seek each other out and it would grow to join up again. The strategy to bypass this grid/minefield of interlaced wire, would be to fire the blaster across it clearing a path and then to run through it within 8 seconds before it regenerates. While it was a bit fantastical for the time, I'm sure some hand-waving could justify nanotech as the way this TV tech might be realised.
- mhalle 10y agoThere was an interesting Science Friday segment on this topic back in August 2016: http://www.sciencefriday.com/segments/a-hand-a-fin-a-gene/ http://www.sciencefriday.com/segments/a-hand-a-fin-a-gene/ A couple of comments made by the guests during the discussion (from memory): * there is a theory that humans/vertebrates actively repress regenerative abilities, * children under the age of about five have the ability to regrow cut-off fingertips, * the genetic instructions for growing a hand (or fin) consist of the thumb and little finger, and the rest get interpolated.
- kingname 10y agoDo you know cancer? The cancer is the ability of regenerate from the very begin in human's history. But we lost the ability of control cancel cells and it became an illness.
- dpark 10y agoWhat is this claim based on? This sounds like speculation.
- Jerry2 10y agoFew years back I remember reading a story about the guy who lost his finger in an accident and then regrew it by dipping it into some kind of a powder. Edit: found it! >The magical formula to regrow a finger apparently includes a doctor, a pig, and some “pixie dust.” This is no fairytale, though; this is a medical breakthrough being explored at the University of Pittsburgh, Pa. In Science Channel’s video, “How to Grow a New Fingertip,” Dr. Stephen Badylak from the university explains regenerative medicine has the potential to grow a whole human body. https://www.youtube.com/watch?v=DtBUM51t4iw https://www.youtube.com/watch?v=DtBUM51t4iw http://www.medicaldaily.com/pulse/magical-pixie-dust-pigs-bladder-helps-man-regrow-human-tissue-severed-finger-346154 http://www.medicaldaily.com/pulse/magical-pixie-dust-pigs-bl...
- sakopov 10y agoPerhaps I'm wrong, but isn't this how scientists regrow organs? The matrix is used as the structure which gets implanted with the person's stem cells which activates growth. In the end the organ isn't even rejected by the body. However, growing limbs out of the same material is just mind-bending.
- mysterypie 10y ago> In Science Channel’s video, “How to Grow a New Fingertip” Just wow! This story is about actually regrowing a finger on the man's hand. It's so incredible, I'd skeptical. Is this really correct? Why didn't they make a time lapse video of the man's finger regrowing -- even taking just one photo per day. That would have been the obvious thing to do, but they didn't do it (or didn't show it). UPDATE: On further research, I guess it was just too good to be true. Here's one rebuttal to the claims from the exuberant video: https://www.theguardian.com/science/2008/may/01/finger.claim https://www.theguardian.com/science/2008/may/01/finger.claim tl;dr: The finger was not so badly injured. It healed rather than regrew.
- Jerry2 10y agoHere's some pictures of finger regeneration. DO NOT open these images if medical imagery bothers you. They're gruesome :) http://www.mebo-international.com/sites/default/files/field/image/Fig%202.GIF http://www.mebo-international.com/sites/default/files/field/... Page with a lot more pictures: http://www.mebo.com/a/books/HUMAN/2011/0221/2934.html http://www.mebo.com/a/books/HUMAN/2011/0221/2934.html These examples are from stem-cell activation therapy: http://www.space-age.com/fingertipregeneration.html http://www.space-age.com/fingertipregeneration.html
- sfink 10y agoFrom what I've understood from things I've read on the past, we do have pretty much full regenerative ability already. It is blocked by various things, such as the epidermis. If you chop off a finger, a blastula of stem cells will develop on the tip, at least until the skin grows over and stops it. If you could hold back the skin, then... well, you'd die of an infection in very short order. Waiting for regeneration is just not feasible in the natural world. There's also the potential for cancer, of course, but personally I don't buy that objection. You can take cancerous cells and revert them to stem cells and they'll stop misbehaving (unless their genetic damage is very specifically triggering them to grow without bound, but I think this is rare. Usually it's a gene activation problem.) And complexity of the regenerated part isn't much of a problem. You can reroute the nerves on a salamander to get a fully functioning arm poking out of its back. Some things can regenerate half their hearts fast enough to survive. I don't know exactly how the information is transmitted and expressed, but it's there. No, I can't prove my assertions. They are based on half-remembered readings of the book The Body Electric from long ago, written by a guy who did experiments to back this craziness up. He was enough of a nutcase that not many people followed after, though his key findings were replicated. And he lost the thread at some point, going on a crusade against emf fields that didn't seem to be based on real science. So it goes.
- logfromblammo 10y agoAs I understand it, scarring and regeneration are mutually exclusive. The advantage of regeneration is that you get the body part back. The advantage of scarring is that you don't bleed to death or get a fatal infection while waiting for the wound to close. In larger animals, formation of scar tissue had a greater survival advantage. So humans scar instead of regenerating. The regeneration capacity is probably all still there in humans, but it is never been observed in modern times, except after losing less than about 1 cm of fingertip. It may not be a matter of how to turn regeneration on, but how to turn scarring off.
- xux 10y agoA lot of people are focusing on the mechanics, but it seems like humans don't generate body parts just like cells don't generate organelles. The entity is not _meant_ to exist by itself, but form a cohesive living group. A cell doesn't need to repair itself, it can simply clone itself and then die. A human being doesn't need to regenerate itself because it can reproduce and be cleared away. Evolution evolved to ensure the survival of the species, not the individual. The human being is constantly generating itself by multiplying cells. Similarly, the species is constantly generating itself by multiplying individuals.
- devoply 10y ago> Evolution evolved to ensure the survival of the species, not the individual. At some point in our evolutionary history the cells in our body made this choice. Evolution favors survival and potentially reproduction, because otherwise you are no longer in the game. So there was some evolutionary constraint that caused those genes not to regenerate parts. It's possible we can change things so that those genes are active again. But we don't really understand these systems well enough to do that and won't anytime soon. But science carries on and I am sure you can make lab mice to test hypotheses of how this might work in mammals. And we probably will very soon, if not here then in China. Evolution is perfectly fine even if you don't reproduce much, as long as you continue to survive in your environment. There are creatures out there that have changed very little and we know this because we have fossil records, and this is because they have been adapted to their environment and stayed adapted despite the environmental changes. And there are even immortal creature that die not because their bodies age and kill them but because they are eaten by other things, but still they don't change much over time. I guess you could say they are better evolved than other creatures that have to constantly change. They made better evolutionary decisions than other creatures very early on.
- piptastic 10y agoYou don't have to regenerate parts to live long enough to have offspring. You can do it at like 15 years old. So evolution isn't going to help in that regard much.
- maxander 10y agoThe "we have the same genes" argument is completely absurd. So alright, some set of DNA sequences in the context of a worm enable the regeneration of worm parts; does it follow that the same set of DNA sequences in the context of a human enable the regeneration of human parts? Of course not! In the same way that the knowledge of how fix a bike has little bearing on being able to fix a cellphone, or that the touchscreen drivers on said phone wouldn't provide a usable interface if loaded onto your gameboy. DNA is just data; its functional value is almost entirely dependent on its surroundings. For that matter, we're a bit physically different than worms; trying to port their mechanisms to human physiology is likely comparable to trying to graft wings onto your arms in order to fly. Not to say that regeneration is implausible (after all, generation is possible), or that there's nothing to be learned from worm regeneration, but this article is fluff.
- naasking 10y agoSure, we have the genes to grow limbs while hibernating suspended in amniotic fluid and being fed intravenously. Maybe recreate those exact circumstances and we can regrow limbs.
- vacri 10y agoWe regenerate plenty. Our bodies are constantly regenerating. We keep growing new skin to replace old (dandruff is a simple example), damaged organs can recover (eg liver problems), and even exercising to increase strength involves regeneration (broken muscle fibres grow back stronger). We don't regenerate large external body parts in general, but we do regenerate some bits quite well - like the palms of our hands. If you cut us, do we not bleed? Then clot? Then grow new tissue to heal the wound? Sometimes so that there is no evidence of a cut afterwards?
- Grishnakh 10y agoThat last part isn't regeneration, it's scarring. If it were regeneration, the skin would grow back just like new. The reason we scar instead of regenerating is to reduce the chance of infection; regenerating, as many simpler animals do when injured, takes longer and leaves the wound open to infection. We opted for scarring to avoid this. As for evidence of a cut afterwards, if you look at the skin under a microscope, layer by layer, you'll probably see the evidence, though it probably depends on the severity of the injury. Anything that goes through all the layers of skin leaves a scar, to my knowledge. As for growing new skin to replace old, the new skin we grow isn't a perfect replacement. If it were, older people wouldn't have wrinkles. We have a limited healing capacity, but it's not regeneration. Regeneration would have us growing tissues that are identical to those we had when we were young, with no evidence of scarring at all.
- Qantourisc 10y agoFrom another research done on mice, the answer is mainly scar tissue. https://www.ncbi.nlm.nih.gov/pubmed/12557217 https://www.ncbi.nlm.nih.gov/pubmed/12557217 About the evolution part: we have a higher change to live with scar tissue, then we have without (shorter chance for infections).
- Mz 10y agoand supply the necessary materials to let it work. That is the key.
- PikelEmi 10y agoBut when then if you cut of an arm - do the body then regenerate a new arm and the cut off arm a new body ?
- chei0iaV 10y agoUnless the arm managed to quickly generate enough organs to crawl around an feed itself, it would suffocate/starve before it could generate a body.
- songgao 10y agoImagine you chop off your head, give both your head and body necessary environment to regenerate. It'd be like cloning. Although the head gets a brand new body that works just as good if not better, while the body gets a head that is completely blank. Sounds pretty unfair to the latter...
- namaemuta 10y agoIf this were possible, I wonder how our new limb would grow. Would it be a reconstruction of the structure of the old limb or would it grow like a child limb and take the same amount of years (18-20) to reach the adult stage of the limb? Edit: replaced limb instead of member.
- Terr_ 10y agoFYI, referring to a body-part like "his member" is often a euphemism for penis, so your post is (unintentionally?) amusing to read.
- namaemuta 10y agoUnintentionally. In my defence I have to say that the term is correct but I get your point. I've replaced it for limb hoping the question will be taken more seriously.
- cobbzilla 10y agoseems to me that when the original generation of organs, bones, and other structure is occurring, there is a chemical soup of proteins/hormones/etc that provides the right environment for a whole host of gene expressions not seen after the generation is done and the organism is more or less fully formed. recreating that environment seems challenging. it's like getting back to bios after you already booted the OS.
- dang 10y agoWe changed the URL from http://newatlas.com/human-body-regeneration-worm-genes/46670/ http://newatlas.com/human-body-regeneration-worm-genes/46670..., which points to this.
- stn 10y agoWhat about unwanted parts which are removed intentionally? Wisdom teeth and appendicitis come to mind. Or body parts intentionally modified by surgery. Basically, unless there is some control regarding which part to regrow, this might not always be desirable.