
Our closest worm kin regrow body parts, raising hopes of regeneration in humans - awqrre
http://www.washington.edu/news/2016/11/28/our-closest-worm-kin-regrow-body-parts-raising-hopes-of-regeneration-in-humans/
======
xux
A 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
> 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
You 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.

~~~
toasterlovin
Living for a long time after you have children is incredibly useful from the
standpoint of genetic fitness. After all, grandparents play an important role
in pretty much every human culture. And a grandparent with all their body
parts is a whole lot more useful than one without.

~~~
coldtea
> _Living for a long time after you have children is incredibly useful from
> the standpoint of genetic fitness. After all, grandparents play an important
> role in pretty much every human culture._

In the time scale that matters to evolution, grandparents played absolutely no
role for the Homo Sapiens, and neither did culture.

~~~
toasterlovin
Do you have children? Raising children is hard. And it's a lot less hard when
you have other adults to help. Historically, those would be grandparents and
aunts/uncles. But aunts/uncles would probably have children of their own.

~~~
coldtea
"Historically" is the keyword here. Evolutionary timespans are much much
larger than recorded history and human culture as we know it.

~~~
toasterlovin
Nobody's saying that grandparents being alive are a prerequisite for
grandchildren. But anybody with kids will tell you that grandparents are
tremendously helpful in raising children.

Evolution is statistical in nature, not binary. Grandparents just have to be
useful in raising grandchildren for them to be favored by natural selection.
They don't need to be strictly necessary.

------
PeterisP
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.

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.

~~~
SilasX
>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.

~~~
PeterisP
For 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.

~~~
chei0iaV
> if something rips off your foot, that's not an injury, you simply bleed to
> death or die of infection

That's a false premise.

Plenty of (four-legged) animals can survive just fine without a leg - in fact,
it's often said that animals have a spare leg. Some animals might even gnaw
their own leg off it's stuck in something and they can't get it out.

~~~
PeterisP
It's kind of correlated with size - the smaller the animal is, the easier it
is to survive after losing a limb. For a horse, even a broken leg is likely to
be fatal.

A missing foot is survivable for a lynx much more so than for a human in the
absence of modern medical care.

The same applies for evolutionary pressure in the case of hypothetical
regeneration. A lizard can take ~2 months to regenerate a limb, for a human it
would take longer simply since the limb is larger and needs to grow more.
Prehistoric humans and hominids were calorie limited - if an injured
individual is capable and likely to (a) survive for e.g. half a year with the
injury and (b) to obtain much more calories than normal to rebuild many pounds
of tissue, then apparently there is no strong evolutionary pressure to favor
regeneration it as he/she is capable of procreating almost as well even
without this feature.

------
sfink
From 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
As 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.

------
Jerry2
Few 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-
bl...](http://www.medicaldaily.com/pulse/magical-pixie-dust-pigs-bladder-
helps-man-regrow-human-tissue-severed-finger-346154)

~~~
mysterypie
> 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
Here'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/...](http://www.mebo-
international.com/sites/default/files/field/image/Fig%202.GIF)

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)

------
reasonattlm
The 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...](https://www.ucsf.edu/news/2015/11/251746/human-gene-prevents-
regeneration-zebrafish)

"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
That 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.

------
traviswingo
I'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.

~~~
partycoder
Well, 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
But 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.

~~~
astrodust
Mechanically 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.

------
avodonosov
It would be good to regenerate at least teeth.

~~~
Turing_Machine
Teeth 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
I'm not a dentist, but I get the impression that milk teeth and adult teeth
are different things, not a regeneration cycle?

------
maxander
The "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
> 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!

But that isn't really the argument. We know we can grow limbs because we've
all done it once before.

------
mhalle
There 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.

------
jtchang
This 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
> 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
Forbid 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
You 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
This depends on the reproduction rate. If it's > 1 then you're right. BTW,
controlling reproduction rate is a way to not overcrowd Earth.

------
mikedilger
The 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.

------
Qantourisc
From 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).

------
namaemuta
If 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_
FYI, referring to a body-part like "his member" is often a euphemism for
penis, so your post is (unintentionally?) amusing to read.

~~~
namaemuta
Unintentionally. 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.

------
vacri
We 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?

------
naasking
Sure, 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.

------
kazinator
"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
This 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
Microchips 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
> 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
:)

------
MichaelBurge
It 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
This has to be a solved problem unless the womb offers some sort of telemetry.

~~~
MichaelBurge
In 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.

------
abledon
One 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-
My...](https://www.amazon.com/Spark-Machine-Acupuncture-Explains-
Mysteries/dp/1848191960)

[2] [http://www.npr.org/sections/health-
shots/2013/06/10/19038548...](http://www.npr.org/sections/health-
shots/2013/06/10/190385484/chopped-how-amputated-fingertips-sometimes-grow-
back)

[3] [https://vimeo.com/26761300](https://vimeo.com/26761300)

~~~
marvy
I 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
Yes! 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
Okay, fine. Then what makes you say that children have more than adults?

~~~
abledon
Its more about the strength and quality rather than the quantity. As we get
older the quality reduces with the rate depending on our genes, lifestyle,
habits etc... Children in general, have better qi because they are 'new'.

I'm not going to go into the scientific details here and start listing off
pubmed studies, but its all in that book if your interested (many references
at the end of each chapter). I'm sorry the amazon link seemed to further
dishearten you, I would love to know why!

~~~
marvy
> I would love to know why

Sorry for late response. The entire blurb on Amazon gives off a mildly pseudo-
science vibe, but it is mild enough that I was willing to forgive it. But this
I could not overlook:

"[...] how the hearts of two people in love (or in scientific terms `quantum
entanglement') truly beat as one"

Just no. I don't know quantum mechanics, but I know enough to say that can't
possibly be anywhere near right, or even vaguely plausible.

~~~
abledon
Ah yes, so, similar to how womens' periods synchronize up when they live
together...Studies of couples show that when in a state of rapport, of
emotional empathy, heart rates become matched and that they become mismatched
when out of rapport: [http://www.futurity.org/heart-beats-sync-up-in-romantic-
coup...](http://www.futurity.org/heart-beats-sync-up-in-romantic-couples/)

Yeah I would probably not take that quote 'Truly beat as one' literally, I
mean, I'm betting the heart rates in the study aren't as precise as to say...
a distributed real-time system written in go /joke :)

~~~
marvy
It's not the "beat as one" I object to, it's the "quantum entanglement".

~~~
abledon
Oh, Rats! Well when speaking about quantum entanglement, we (as Naive realists
on HN (see my profile)) should just ignore it for the next 2000 years,
hopefully by then physicists will have a definitive yes or no answer for that
domain. Like an unfortunate cardamon seed in our tasty sweet rice kheer, I
guess just navigate around it and enjoy everything else presented in the book
with a back-up-with-references-from-pub-meds-from-the-last-40-years format.

~~~
marvy
All right, all right :) I'm adding it to my list.

------
PikelEmi
But 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
Unless the arm managed to quickly generate enough organs to crawl around an
feed itself, it would suffocate/starve before it could generate a body.

------
stn
What 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.

------
agumonkey
Watching 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.

------
cobbzilla
seems 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.

------
woofyman
Lizards can regrow their tails.

[https://www.google.com/amp/s/www.geneticliteracyproject.org/...](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)

------
songgao
Imagine 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...

------
Mz
_and supply the necessary materials to let it work._

That is the key.

------
dang
We 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.

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kingname
Do 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
What is this claim based on? This sounds like speculation.

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partycoder
Probably 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.

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dpark
> _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._

Lemmings don't commit mass suicide.

[https://en.m.wikipedia.org/wiki/Lemming#Misconceptions](https://en.m.wikipedia.org/wiki/Lemming#Misconceptions)

~~~
partycoder
OK, fine. Disregard the lemmings.

They do die massively, but it's not intentional, I get it.

