- A recent study identifies phenotypic plasticity as the ability of tadpoles to change how they look and act, and how their tissues function, in response to their environment. If the pond also contains fairy shrimp, some tadpoles turn into aggressive carnivores and sometimes, the carnivorous tadpole stage becomes entrenched – without the need for a dietary trigger. This plasticity has also been confirmed in lizards, roundworms, and yeast. When yeast is exposed to the herbicide paraquat, the yeast copes by eliminating some or all of the DNA in their mitochondria, the cells’energy-producing organelles.
- Some consider this a classic example of “plasticity-first evolution”. On the surface, the findings vindicate Lamarck. The plasticity those changeable tadpoles display is built into their genetic code. And when an “acquired” trait does become “permanent”, it is because of mutations that “fixed” the plastic trait – a process biologists call genetic assimilation.
- Since plasticity is a built-in trait of so many organisms, it has obviously been mistaken for “evolution”. “Permanent” claim is meaningless given all organisms populations are ever-changing. The main questions are “what are the limits of plasticity?” and “what happens over the very long time?” The evidence to date is very clear:
a. Plasticity is a built-in widespread if not universal characteristic of organisms
b. It is limited in scope to a few traits like color, behavior, and metabolism
c. Plasticity is reversible rather than cumulative
d. It is not divergent as toads, lizards, roundworms, yeast, etc. never turn into not-toads, not-lizards, and so on. - This is a repackaging of the same stories sold as proof of “evolution”. Darwin’s finches, the peppered moth, antibiotic resistant bacteria and, why not, the tanning humans. Too bad all these not only do not diverge into new organisms, but they all have been shown to revert eventually when the stimulus is removed. Finches change back their beaks depending on environment and never turn into non-finches, the black moths reversed to white and never to not-moths, antibiotic resistance disappears from the population when we reduce the use of antibiotics (see NIH recommendation), and neither light-skinned Nordics, nor dark-skinned Mediterraneans turn into not-humans under any circumstance.
https://www.nih.gov/news-events/nih-research-matters/reducing-antibiotic-prescriptions
Yes. You use the concept more properly referred to as variance. Therefore, you confuse the two.
Why is that realistic, as a principle? Do you think evolution consists solely of ‘engineered populations’ released into the wild? You seem to be arguing against ID in that case.
They may either die out or persist. But what will not happen, if their lineage persists, is that their mutations will simply reverse and they will become wild-type again.
‘Seems to’? Is that like ‘Appears’? 🤔
Recognising separate phenotypic and genetic components is pretty standard. It was ‘made up’ by the very same people who coined the broader concept of plasticity: geneticists.
Suppose a population is reduced to 4 members, then recovers. What has happened to its variation (variance) and its mean? What is it going to ‘revert’ to when it grows again, and how?
Oh good. A game of burden tennis.
Could you please please, with sugar on top, explain how regression to the mean prevents evolution from occurring, because I don’t understand how it works?
Better?
Picture from the 1886 Galton paper.
See Allan’s comment. You haven’t addressed that comment, just changed the topic. If you are unwilling to defend it, you should revoke it.
“You can’t be seriously asking for my counterfactual to your unsupported claim. That burden is entirely on you.”
Just giving you the reasons why I don’t accept your claim that all population change is just phenotypic plasticity. If you don’t care, then don’t bother making those claims here.
Did I say “Read again the source article for this OP”? What part of that didn’t you get? Or you read and didn’t understand what they say?
I did NOT use the concept. But go ahead and keep pushing against that wall.
It’s realistic because it’s a feasible experiment as opposed to a dumb unverifiable legend you guys tell about some hypothetical distant past.
Don’t just make up stuff. Go ahead and test and THEN report your findings.
Suppose not! Test! Observed natural experiments also count.
You’re in denial – I already gave you a lot of examples. And it’s “Regression prevents Divergence” for now. Of course, no divergence, no “evolution”.
And what is that picture telling you?
Corneel,
Now you’re not even trying. Was expected at some point.
Am not!
That’s false. Directional change in a single lineage also is evolution.
THAT is the famous “reversion to the mean”, the very first time it was presented in a paper. It tells me that some of the variation in height is heritable, and some of it is not.
Your turn. What does that picture tell you?
Do you really think a shrinking population has never been observed to lose variation? As an observed natural experiment?
Allan presented the correct counterargument why reversion to the mean does not prevent evolution from occurring (and yours truly mentioned it a couple of times as well). Why do you refuse to engage it or even attempt to understand how the argument works?
Did too. Variance is a measure of variation. When repeat samples regress to the mean, it is because there is more variation outside of the tails of the distribution than in them. There is simple ‘variation’ both to left and right. But the central tendency is down to variance.
You think it unfeasible that anything could affect populations except engineered populations released into the wild?
Of course height is partially heritable. 7 ft people are not expected to give birth to 5 ft (adult) children. That doesn’t change anything.
Huh? First, there’s no documented “directional change” and second, are you saying “divergence of character” is not a cornerstone of “evolution”? Then what is?
Did not. He imagined a hypothetical case with too many suppositions. But we do have experimental evidence of bottlenecks, and none shows “evolution”.
Huh? Start making sense.
Huh? Start making sense. And refer more to experimental evidence and less to your imaginary scenarios.
Are you kidding? That changes everything. The heritability of trait variation is what preserves any change to the population phenotype, and shows that “reversion to the mean” will not be occurring once the genetic composition of a population has been changed.
For divergence we require at least TWO populations, do we not? You are making an artificial distinction between divergence and within-lineage change, but they are the same thing. If we have two populations with directional change in opposite directions, or have only one population changing, then we observe divergence. If neither of them changes, then there is no divergence.
Too many suppositions, how so? Allan presented a scenario where a population departs from the mean. Isn’t that the very subject that we are discussing; Whether such populations revert to the mean or consolidate the phenotypic change?
Allan argued that a population that is strongly reduced in size will lose genetic variation. This is observed many times; it is a major conservation issue, with cheetahs being a famous example. It is perfectly fine to use that as an example. Are there any other “suppositions” you resist?
What are you talking about? Reversion to the mean is not quote-unquote, but a real thing unlike “divergence of character”. And this is how it works: if you’re 7′, your kid is (probable) 6’6″ and will (probable) find an average mate (say 5’10”), hence your grand kids become 6’3″ and so on until your descendants are just average in a few generations. Your height is NOT PRESERVED over generations.
That doesn’t make any sense. What “two populations”? What “within-lineage change”?
And you should really (REALLY!) consider using real life examples, not 100% artificial scenarios.
So that’s a good one – finally a real-life example. Is the contemporary cheetah “diverged” from its ancestors? Of course not? But why? Because there’s no such thing as “divergence of character”, that’s why!
And anyway, to prove your theory you want to show an example of post bottleneck full recovery “divergence”, not one that has not yet passed that critical point.
This makes very clear how you suppose it works, thank you.
What you just described is the common way regression to the mean is often misunderstood. Francis Galton himself did not share this view, by the way, for the following reason: If we follow your scenario through, then all variation gets diluted and disappears in the course of a few generations. We call this blending inheritance. Yet Galton, like you yourself, recognised that this doesn’t happen: the variation in height is preserved. There is no difference in the variance in height between parents and offspring, and we expect as many extremely tall and short subjects in the offspring as there were in the parents. How is that possible? The trick is in the fact that, although the mean height of children in a family tends to regress to the mean, there is variation within families as well which offsets the diminished variation among family means.
Now please work your way through Allan’s scenario. What happens when there is a difference in the mean of the breeding parental generation? If you are looking for real life examples: This procedure has been exploited by breeders for centuries.
Not my fault you struggle with basic statistics.
Just running over the basics, which requires examination of core concepts. You have experimental evidence that all that has ever happened in nature is release of engineered populations to the wild? ‘Course you don’t. So why is it a reasonable extrapolation, just because we have some data relating to that scenario? I think that’s placing an unjustifiable faith in the model – classic map-territory confusion.
If you release a selected population into the wild and change the selective landscape, you are varying 2 parameters, not 1, a classic flaw in experimental design. If you release beneficial alleles into an environment in which they are no longer beneficial, of course they will be lost. Is this a reasonable universal model of evolution? I don’t think so.
Because you are in a wider, sexual population. The scenario I am inviting you to consider is one where there has been, effectively, truncating selection. The wider population no longer exists to pull us back to the mean. So what does?
I know this is artificial. It is extreme for illustration purposes (and based on a scenario you yourself proposed). Many more realistic scenarios could be proposed, but I think it often helps to consider extreme cases. It’s not a dichotomy – ie, either it’s unrealistically extreme or the population must have a constant mean.
How many experiments have you conducted?
The nature of many of the LTEE mutations is such that they are not simply reversible – wholesale transposition is vanishingly unlikely to reverse. Without conducting a single experiment, you are sure that they are, and I have to prove they aren’t. ‘Twas ever thus with the ‘experimental evidence’ crowd. Hypocrites, the lot of ’em.
You should really forget Galton… or Darwin for that matter. There is no “trick”. If your family is 7′ tall, [almost] ALL variation will be to downsize. Hence the list of 9′ tall is NULL, 8′ is very short, and so on: https://en.wikipedia.org/wiki/List_of_tallest_people
Yet the “trick” is that breeders have NOT mutated one single organism to date even with the most recent technology. In addition, all pure-breeds are very weak and take great effort to keep alive.
If you “change the selective landscape”, then you DON’T “release … into the wild”. No such thing as “beneficial alleles”. Name one if disagree. There is no “reasonable universal model of evolution” – and that’s exactly your problem.
What “truncating selection”? The “selection” fantasy has been discussed elsewhere. I will not discuss your unrealistic scenarios. Only observable evidence – even the sciencemag article is based on EVIDENCE – misinterpreted of course.
Enough talk. What’s your bet for what happens when you release the LTEE eColi into the wild? And let’s make this interesting.
Reality check: If families with mid-parent values of 7′ tall almost exclusively produce offspring that is “downsized”, then one of the next generations will eventually end up with an empty list of 7′ tall people. This process will repeat until all variation has vanished. Think about it. Something is wrong with your scenario.
BTW. When will you guys start using the SI? METERS!
Why bring up mutations? There is sufficient standing genetic variation to work with.
Why don’t they revert to the mean and live healthy and happy lives?
The very act of releasing a population that you have subjected to directional selection into the wild changes the selective landscape for that allele. The directional selection you have been applying is relaxed, and so selection will not maintain the allele. Therefore the behaviour of alleles on wild release is not a sound model for wide application to all scenarios.
Cit+
And yet you are saying that reversion to the mean is a universal, worked out all by your little self using the magic of inductive reasoning.
Sure. No such thing as truncating (or -tion) selection.
You’re changing the selective scenario. My bet is that Cit+ will go extinct.
Yours?
Not so. That’s because the 6′ and even 5′ family has a small chance of producing 7′ offsprings. This is real life, not a theoretical scenario.
When necessary.
Huh?
Because someone puts a LOT of effort in perpetuating those pure-breeds.
Again, “selection” is the wrong concept, hence your logic is circular. If “beneficial mutation” were a thing, then it would hold even if the environment changed.
Obviously that’s a trade-off mutation at best, given that it has not already spread to ALL eColi. Therefore not a “beneficial mutation” in the Darwinist sense.
Just a plain sight observation. No need for inductive reasoning. Go ahead and dispute that if you can.
Let me remind you that breeding is much more than “selection”:
5. Plant and animal breeding is not the “artificial selection” described by Darwin and has nothing to do with any natural process. Breeding requires a desired outcome, selection (just a minor step!) and isolation of successive generations of promising individuals, active mating or artificial insemination, optimization of growth conditions for the selected individuals, and/or other genetic technologies. Without most of these active steps nothing happens. Chihuahua and Poodle have no superior survivability to common dog or wolf, but happened anyway because humans worked hard to make them possible. But no one ensures all these active steps in nature. To take only one example, how could humans have “evolved” distinctly from chimps when no one separated each and every new generation based on a teleological model? Why did the proto-human not mate back with his/her regular chimp cousins to put an end to the split? Who and how could have separately optimized conditions for both chimp and human so both lineages survived in what looks like very much similar environments? ‘Selection’ of both “artificial” and “natural” type is thus the wrong word and should be phased out.
Of course “Cit+ will go extinct”. That’s because Cit+ is NOT a “beneficial mutation”. And that’s because there is NO SUCH THING as “beneficial mutation”.
Nonlin.org,
There are benefits to having the adaptations necessary to live and reproduce in the niche an organism finds itself in. The ability to swim underwater efficiently is beneficial if you live in the sea. Not so much if you live in a desert.
Good grief no. It is entirely dependent on the environment.
Absolute tosh.
Will do.
Nonlin.org,
Stop quoting yourself.
Whatever you say, big guy.
Is the chance that a family with a mid-parent value of 6′ produces 7′ offspring so much larger than the chance that a family with a mid-parent value of 7′ produces 8′ offspring? Most peculiar! What causes that?
Quoting Freddie Mercury: “Is this the real life? Is this just fantasy?”
A most eloquent response again, communicating some gap in understanding, perhaps? What part should I explain?
Perpetuating, perhaps, but those stocks do not phenotypically revert. That’s why they are called purebred or true-breeding.
You are failing to give satisfactory responses to simple issues that have had an explanation for over a century, Nonlin.
Not how it works. You only build myths around the observable. But there’s nothing in the observable that tell you about how and why things are the way they are.
If “it depends”, it means it can be ‘detrimental’ instead, hence NOT “beneficial”. Logic 101.
Why don’t we take your word for it?
Which is it? Your word or my argument?
Yes, the same change can be beneficial or detrimental depending on the environment. Hence mutations happen irrespective of the ‘need’ for those mutations, right.
So oh wise one, why are things the way they are? Where would you like your delivery of gold dropped off? Round the back is it? Next to the furs and diamonds!
Or are you saying we can know nothing about the way things are and were?
Pangaea much?
Do you disagree but don’t have valid counterarguments? What can be “peculiar” about indisputable observations? I already demonstrated what causes that.
Actually, they do. I distinctly recall an example of inbred lab mice losing their characteristic through mutation and thus becoming useless. Can’t find that actual quote, so this is an imperfect substitute: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3627018/
So a single example demonstrates there are no such thing as purebred mice?
Someone better let all those people who have been selling such mice now for what must be 100’s of generations. There are entire companies that do nothing except breed such mice. How can they possibly do that if what you are saying is true?
Don’t let reality get in your way or anything…..
Yes it is.
I bet you wouldn’t have looked in Galileo’s telescope either. 🙂
And your point is?
We can see how things are NOW (clear mark of design). We cannot see how and why things HAPPENED (“evolution”). And we most certainly can’t see “beneficial mutations” like in the example given: “ability to swim underwater efficiently is beneficial if you live in the sea.” Sponges, mollusks and corals show why that’s not the case.