Do we know how a human would regrow a limb? Would it start out as a small limb and grow out or just grow arm first then elbow, forearm, etc.
https://jbiol.biomedcentral.com/articles/10.1186/jbiol105/fi...
It's fairly reminiscent of how limb growth looks during embryogenesis - and I think considering that is how other vertebrate (such as axolotl) regeneration looks, that it's probably what human limb regrowth would be like too. So your second description sounds more like it, but with continuing development of 'prior' parts while the 'later' parts (fingers etc) are still developing.
Michael Levin's group have experimented with a 'bioreactor' that can be attached to the stump of an amputated limb in frogs (that don't ordinarily regenerate limbs) and after a short period of treatment (days), the reactor is removed and the limb then regenerates on its own over the next few months. They are looking into reproducing this in rats now, with the clearly-stated aim of similar human regeneration being the ultimate goal.
I wholeheartedly recommend watching some of Levin's lectures on YouTube, there are a great many of them and I think they're both illuminating and fascinating!
We should really just grow clones in labs and harvest them for parts.
Remove the brains at week 16 through genetic and surgical means. Keep the rest of the body artificially alive. Expensive upfront, but massively scaleable.
MHC, ABO, etc. complexes engineered to be transplant compatible.
We could replace organs and blood as we age. In fifty years, full head transplants could tackle every disease except brain and blood cancers and neurodegeneration. Every other disease solved.
It's so simple and obvious, but nobody can get over the egocentric morality qualms and superstitious ick factor.
Our bodies are plants. It's our minds that are special. We should be able to transplant every other part.
The gut has the enteric nervous system with half a billion nerve cells and a hundred million neurons. Where's the clear divide between 'brain' and 'everything else'?
> "full head transplants could tackle every disease except"
except being quadraplegic and in an Iron Lung because reconnecting the spinal column is indistinguishable from magic at this point. What about the risks involved in major surgery and rehab? The hospital staffing and effort and costs involved in doing multiple organ transplant surgeries per lifetime for each of hundreds of millions of people? Saying "it's so simple" doesn't make it simple.
But by using only three of the four factors, you can still induce pluripotency, but with much lower cancer risk.
I think that cloning individual organs is much more promising than cloning entire bodies and then harvesting. Much less work, you don't have an entire body you need to either upkeep or dispose of.
Ever notice as we age, get hurt, that table, network, updates?
For some injuries, part of the imperfect process, is a relearn, recalibrate step involved. Once that has played out. The whole thing works as a unit.
I can sometimes remember what it used to be like. Being able to move jn some way, or some rate.
And when I try and do it today, there is a very deep inhibition. My brain / body knows it no longer happens that way,
And these things may be why physical therapy helps. No pain. No gain. We have someone else pushing us. Manipulating our bodies in ways that challenge those built in metrics.
So, it hurts, but it is good hurt. Triggers that network to reconsider, update, whatever.
But for getting us into a ridiculously drawn out war, and another war, and…oh and paving the way for drone strikes, for helping lead the country into a recession, for being - at the time - really good at embarrassing the office, he still pretty much gets to just paint or whatever and fuck off.
A bit mad to think about how much I miss him compared to gestures at everything. “Mission Accomplished”, vomiting on (iirc) the Japanese PM, being oddly good at dodging shoes to the head, this is like seeing a toddler destroy a car and going “cuuuuuute”.
Cheney, on the other hand, shot a guy in the head “on accident” and by my count has no redeeming qualities unless…nope, just checked and he’s still alive.
Pluripotent cells work fine in many animals with no apparent problems and avoid all of the issues with the clone approach. If pluripotent cells turn out to cause problems, then we could always engineer a kill switch to make sure they die off after the limb is regrown.
It seems more likely for there to be a single set of genes responsible for growing a limb than 2 sets in the Axolotl. Especially since the new limbs seem identical to the old ones, rather than following a distinct backup blueprint.
I’m obviously not an expert.
There’s actually a theory that hominid ancestors at some point split off from other great apes by also not going through the typical great ape sexual maturity. For examples humans look a lot more like juvenile chimps that we do sexually mature chimps.