I don’t think you have used the word “evolved” in the same way that Evolution uses it. It does not mean “change” – although there are changes. For example, a rock changes from a lumpy, perhaps crystalline form into a smooth, shiny form because of erosion, but there was no evolutionary force in play.
Evolved in the sense I understand Evolution to use it is that there is a mechanism that produces variants and those variants have one of four outcomes:
they fail in the environment, i.e. they die.
they survive and their variance helps them surpass their neighbors
they survive and their variance causes them to fall behind their neighbors
they survive and their variance does nothing for or against them
I should have put “die”, “survive”, “surpass”, “fall behind” and “does nothing” in quotes, since they all beg for a nice clear definition, but I don’t have one.
Johna
I don’t think this is what Evolution is about, or at least it’s just a part of Evolution. This part of is incorporated into Evolution: “qualities amenable to lasting will last”. That’s true, but it requires another part: that variants are actively produced. And I think the order is significant too:
variants are actively produced
some of the variants survive (i.e. they last), some do not
repeat 1 & 2 as long as there are variants producing offspring
So, again, the universe changes second by second, but that is not Evolution. I have offspring that are a combination of me and my mate, and that offspring survives a climate change – that’s evolution.
Yup. I’m going for door #1, tautological truisms. (but see below…)
Yup, again. The question then is: Is “death” equivalent to “not life” for all possible definitions of “life”? Seems to be so.
Very cool. The parents are “dead”, and the new organisms are “alive”.
Hmmm.
So that hints that “life” is “life” across the universe, whatever the definition of “life” is. And ditto for “dead”. That is, if something is defined as “alive” on one planet, it could not be called “dead” on another. Or am I jumping a little far?
Let’s see if I understand what you said:
A single entity could arise that provides all variants needed for all (or at least most) environmental changes that happen on some planet. Once that entity is in place, there is no further need for mutations, crossover, or even reproduction. It can survive without changing, and since it can survive, there is no need for offspring.
You’ve come up with a counter-example then. Evolution is NOT universal.
Could that entity arise without evolution? It’s highly unlikely, but it is possible.
Yes. So to paraphrase: “Shit happens… everywhere.”
I’m not sure I understand what scenario Johna is setting up. Correct me if I’m wrong but I get that he is allowing for sexual reproduction and a universe that can change. Seems to me that it would be impossible to not have evolution even if you have unlimited resources.
I think Johna’s definition of evolution is too narrow. I like Sage Rat’s better. It’s simply change in the organism that gets passed down enough to see new traits. Eventually, this can lead to new species.
There are many mechanism for this. Johna keeps talking about mutations but what mechanism for mutation does he mean? For example, sexual reproduction specifically engineers ‘mutations’ during meiosis and then fertilization. Crossovers are changing the genome on purpose. Even if the coding region of the gene is not altered, it got thrown onto the other chromosome and may be expressed differently.
Even if there’s no ‘natural selection’ due to competition for resources, I think populations must eventually drift even if they’re not small and isolated. Also, you would have to eliminate natural disasters or diseases (particularly viral diseases that can alter the genome, some think eukaryotes came from this) that create catastrophic changes in populations. Then you have to remove mate preferences. I suppose this may not exist without competition.
But really, sexual reproduction wouldn’t exist without natural selection and competition. It uses too much energy and wouldn’t be worth it without the pressure for variation.
Finally, to prevent evolution even without sexual reproduction, you’d still have to have a perfect form of replication. This could only exist in a fantasy world. In other words, people can see evolution of self-replicating RNA molecules in the test tube. Mutations are made by mistakes in replication. They can speed this up by putting two different RNA molecules in the tube and limit resources (nucleotides). Eventually the ones that use the resources the best, are selected and the other ones are lost from the population. Nevertheless, I suspect that you might see some population drift even without selective pressure. Even if we suddenly had cellular organisms that have higher fidelity polymerase (how would they originate, BTW?), you still get mistakes. Also, mistakes happen during cell division (called aneuploidy). Either way, changes will occur and eventually populations would likely shift.
The actual word “evolution” is perhaps a bit too tied up in biological evolution, so let me say that there’s a greater law that can be stated like this:
The Law of Existence Any observable object exists in its current state due to the outcome of all reactions with its environment until that point in time.
The main thing to note with this law is that it doesn’t define what an object is. There is no “success” or “failure”. It’s simply pointing out that change or the potential for change was always there, but it made its way through in just the right way to show up just as it is now.
Biological evolution, however, attempts to define what that object is (i.e. a lifeform). Generally, reproduction and inherited traits are part and parcel of that definition. But if a lifeform evolves into something that no longer breeds, but rather lives eternally, is that still “life”? That becomes a little hairy. A definition of life that I think everyone could agree with is that it is something which can operate autonomously (i.e. it has something like intellect).
Well so let’s take either example.
Life = Something which passes on inherited traits to its successors.
This implies change from generation to generation. So, for any line of succession, you’re going to see a reaction with its environment (per the Law of Existence) that could have rendered it no longer fulfilling the definition of life or continuing to exist as life. In either case, the result conforms to the popular conception of evolution and by definition, any “life” you ever find in the universe will have absolutely undergone this process.
Life = An autonomous, on-going chemical reaction
An autonomous being, by the definition of autonomy can be said to have the potential to end its autonomity (for instance, by killing itself or by reacting to its environment in a counterproductive way). Since its assumed that the environment is or has the potential to change, we can presume that an autonomous being is changing itself to persist or else it would have ceased to exist. It might not end up needing to change, but by definition it had the potential and would only have gotten to this point if in all cases where change was required it had acted correctly to preserve its autonomy.
Does the second version count as “evolution”? It’s changing to match its environment and only continuing on as life due to that success, so it can be said to be evolving–even if its due to rationality rather than random chance.
If you phrase the definition of evolution as “The Law of Existence as perpetuated on life” then yeah, no matter what you’re talking about evolution. Not using that definition though, it comes down to whether you would count #2 as being a viable definition of life. It’s theoretically possible that a whole bunch of matter collided at one point and it all just happened to merge correctly to create an autonomous being, and that being has continued to exist into modern day. Personally, I would find that highly unlikely because any lifeform capable of properly changing to match all possible changes in the world in a rational and successful fashion is going to be too complex to happen by random chance. It will have had to have been a lifeform of type 1 at some point.
JohnA, to answer briefly: I think that the answer to your question is that it’s unknowable whether life evolves on other planets as it does on ours until/unless we get to those planets and find out. There’s a missing issue in your OP regarding life, to which I would add (in the form of a question) “as we know it?”. Life can conceivably exist in many forms that we don’t know since we know nothing of extra-terrestrial life, therefore we can’t know whether it evolves as life does on our planet, in other ways or not at all. If it’s life as we know it then it evolves as it does on our planet, if it’s life as we don’t know it it may not.
Hmm. I didn’t think I was referring to my own personal definition. In any case, I meant good old Darwinian evolution.
Simple change through what mechanism? My question is: Must the change you are referring to occur because of mutation and crossover?
I didn’t specify a mutation mechanism. I don’t think Darwinian evolution specified it either. It is possible, for example, that a species could use some other mechanism than DNA for encoding traits and, if so, mutation would not be mutation of DNA but a mutation of whatever encoding mechanism they are using.
But whatever mechansim is used, must mutation (or crossover) occur for a species to adapt?
Well this is actually the core my question. If not by crossover and mutation, how would the population “drift”?
True. But my understanding is that mutations are also caused by exposure to radiation like ultraviolet light. Am I correct (not sure)?
Not necessarily. If adaptation is universal, then one or more mechanisms for achieving that adaptation is universal as well.
Hmm. I didn’t asked whether life as we know it is on another planet or evolves as life does on our planet. I asked whether evolution is universal. There is no presumed definition of life in my question.
To me evolution works like this:
In the face of my environment, I either live long enough to produce offspring (via self-replication, mating, or whatever) or I don’t.
there is an encoding mechanism that defines which set of traits I have
My offspring have a different set of traits than I do because either a mutation or crossover or both were applied to the encoding mechanism.
My offspring faces the environment – which has changed-- and lives or dies long enough to produce offspring. Their odds of surviving are different than mine.
and so on.
(If I am wrong, please correct me!)
Note I haven’t specified carbon-based, DNA, or anything else that is localized to earth-like life.
Evolution’s “survival of the fittest” and “natural selection” is the “Their odds of surviving are different than mine” part and is basically a numbers game. If the traits I have and share with my species increases the odds of me surviving my encounter with the environment and produces enough additional entities to add to the population, great(!), my species continues to exist. Otherwise, the population will dwindle until we are extinct.
Another key aspect is that evolution is passive. It’s passive in that there is nothing that actively selects which mutations occurs, it’s just luck my set of traits happen to be survivors in this environment. Change the environment back 10,000 years and perhaps I’d be a goner.
I think we have established the following are universal facts simply because they are tautological:
there are entities out there that are alive (although perhaps not life as we know it)
there are entities that are dead, i.e. immortality is not allowed.
there is an environment that entities exist within.
the environment changes (perhaps slowly, perhaps quickly)
entities have traits
the traits entities have will allow them to continue being alive (i.e. survive) or not
And so my original question is then: Can I add one more item to this list?
the traits must change through some mechanism to adapt to environmental changes
John
Johna: Okay. I think I understand where you’re coming from and agree that evolution is probably universal wherever life exists. The nature of the evolution, the speed at which it occurs and the variety of species (if that’s the right word) it produces doubtless varies widely from one planet to the next, though given the number of stars in the cosmos there’s probably a likelihood of there being a large number of planets with life similar to the kind we have on earth, however this is another topic. In a general sense I think you’re right. Then there’s the larger issue of whether or how much we can discover of life in the universe outside our solar system, once more, a different discussion.
But Blake came up with a scenario, which I paraphrased above:
If he/she is right, evolution is not universal. It is a counter-example showing that an entity could be adaptive to environmental changes without changing the set of traits it carries, it only has to be able to manifest/present different behaviors from a single set of traits.
An earth-based example is an animal that could transform it’s physiology to be cold-blooded when it was more efficient to be so and warm-blooded when that was more advantageous.
Blake’s scenario seems to be a counter-example to evolution, but there are still a couple questions:
could Blake’s entity arise without adaptation in the first place, i.e. it would adapt for “a while” and then stop when it got to its final form.
my gut feel is that it is too complex of an entity and that evolutionary adaptation is simpler and therefore much, much more likely. There seems to be a general principle of minimization of effort and complexity present in the universe. Something as complex as Blake’s entity runs contrary to that principle. C
John
It’s really impossible to say because we have absolutely no idea what form life takes elsewhere. On Earth organisms adapt primarily through altering their genetic makeup. Adaptation trough Lamarkian mechanisms, while ubiquitous, accounts for a tiny fraction of adaptation. On Earth the genetic material also exists primarily in a single package, with just a few accessory packages, and replication of these package is all-or-nothing
But there is no reason to believe that is universally true. Elsewhere Lamarckian mechanisms may be the norm, and genes may exist as discrete, modular units. The progenitor organism may have had the ability to replicate, multiply and modify individual genes without nuclear division, and to express only specific genes. Total, two-way genetic transfer may also be the norm, since with absolute control of expression genome size becomes less of a burden.
IOW the norm would have been for single celled organisms to modify their own genes without replication. If the temperature is too to they would play around with expressing alternative heat resistance genes, and then play around with making variations on that gene via imperfect replication. They would also swap total genetic material with any other organism they encountered, presumably with a mechanism to remove any perfect copies of extant genes.
Within a relatively short time organisms will exist that have the potential to exist in any environment simply by altering gene expression.
I’ve never heard of this principle before. Where did it originate.
On the face of it, it seems obviously untrue, or at best untestable. It seems obvious that both an oak tree and an alga can live on the same patch of soil, yet the oak tree is much more complex. Similarly numerous organisms have existed over evolutionary time that filled exactly the same niche, yet later forms were usually much m ore complex.
So the only way that this principle could be true is if we define “minimisation of effort” as "minimisation of effort required to successfully compete, but in that case it can’t be brought to bear on this argument without become completely circular.
The way I see it, only two modes are even imaginable for the emergence of complex life-forms: Evolution and creation. Can you think of a third? IOW, if evolution is not universal, that would mean God exists, and decided to create living things on some worlds and let nature take its course on others; which is not entirely inconceivable, but is kind of hard to get one’s mind around.
Depends how you define evolution. For most of my adult life, and in most textbooks even today, evolution was defined as “changes in gene frequency within a population”. I can think of numerous ways that complex lifeforms can emerrge that don’t involve either creation or changes in gene frequency within a population. I gave one example above.
Heck, there’s no reason to believe that extra terrestrial life even has genes.
Well it’s an observation I’ve personally made that seems generally true – not a principle with a capital “P”. It’s the opposite of the universe tends toward high entropy and it’s what makes Occam’s Razor generally true. Perhaps it would be better to call it a rule of thumb.
[QUOTE]
It seems obvious that both an oak tree and an alga can live on the same patch of soil, yet the oak tree is much more complex.
I think a better comparison would be two variants of an oak tree, where both can exist in the current environment, but one of them requires extra complexity (say a symbiotic relationship with another entity). Given all possible scenarios of environmental change, what are the odds of survival for the one kind of oak tree vs the other? I’d bet on the simpler variant.
Yup, you’re right, my argument is circular. Hmmm…
Well we’re back to it again. Evolution is no universal, there are other mechanisms for entities to adapt to environmental changes.
If you have any evidence to support that contention I’d like to see it. I know of none.
And I can’t think of any logical reason why it should be true. Extra complexity provides an organism with extra options, which should increase survivability under scenarios of environmental change. In the real world there is a significant, though weak, correlation between environmental stability and plant polyploidy, with polyploidy being most common in seasonally dry, temperate regions and least common in tropical rainforests. The standard explanation for that is that polyploidy, which is one measure of complexity, provides a survival advantage by allowing a plant to adapt to changes more rapidly.
Now while that argument is disputed, the very observation does provide an objective counterpoint to the idea that complexity is generally detrimental to survival. If that were the case it’s hard to see why polyploids exist at all, since at best they would be survival neutral yet undeniably more complex.
Not saying you’re necessarily wrong, just wondering what observations might have led you to to this conclusion.
Depending on how you define “evolution”. Indisputably there are mechanism other than Darwinian genetic evolution, but that has been firmly established for over a decade.
However I do think there are some observations that support it.
One is that the things tend towards entropy. A clean, orderly room will eventually become messy unless some energy, some effort is expended to keep it clean. To me, a complete breakdown of an object into it’s constituent parts is the antithesis of complexity, it is the simplest form it can take.
Combining those basic parts into a complex entity takes some energy, and some luck. The simpler entities pair up by chance in a particular way and a more complicated entity results.
Another is that resources are scarce. If an organism can survive with fewer resources that’s a survival advantage. If a complicated organism doesn’t require more resources than it’s simpler cousin, great! Otherwise, it will be impacted by it’s more complicated structures.
Once an entity is more complicated it starts to require more from it’s surrounding environment. It has to “eat” for example. Eating is, I think, a complicated
function. Even the simplest form of eating where one organism just envelopes another and then disintegrates the other (“digests”) is a relatively complicated.
In short, energy is required to create something complex and then energy is required to maintain that complexity and then even more energy is required for an organism to self-sustain it’s energy levels.
True, a more complicated organism has more options. But extra complexity also gives more ways for the organism to fail and they require more energy to maintain. So extra complexity is balanced by the extra cost of maintaining the complicated structures.
So in a rapidly changing environment, having many options at your disposal is a survival advantage. And in static environments it isn’t a survival advantage and so goes away.
So in the tropical rainforests, there could have arisen more complicated organisms (simply by chance), but they died off? So given a specific environment or slowly changing environments, simpler organisms survive a little better. Given a quickly changing environment, a more complicated organism survive better.
Some benign traits will be carried if the organism can maintain those traits without impacting its current survivability. If those traits don’t require it to do something (eat more, generate more heat, etc) that will indeed impact it’s current survivability, the traits will stick around. If the cost of maintaining the trait is exactly zero, then it can will keep it around forever. If the cost is greater than zero, then there is a chance in some future environment that extra cost will impact survivability.