Evolution Not Random

[JEROME DA GNOME]

This is an utterly absurd and pointless argument over semantics. It's as if you've got a guy from England and a guy from Spain, and they see a black shirt:

"It's black." "No, es negra!" "No, it's black!" "No, es negra!" "No, it's black!" .....

Interesting that a good amount of conversation was devoted to using a particular definition of a particular word when dealing with opponents in a debate.

 

[Belz...]

I've just read through the thread today. There are clearly different definitions of random at play here amongst parties who have been battling though many threads. I'll not wade into the middle of it other than to state that I agree with Meadmaker; words can have more than one meaning. Evolution can be correctly described as either random or non-random depending on what definition of 'random' is being used.

Which is exactly why I asked Mijo and Jimbob to explain what they mean by random:

1) Deterministic and entirely causal, but impossible to predict by us.
2) Random in the sense that they are acausal i.e. like quantum fluctuations.

That is not the opinion of the average physicist these days.

At least, not the ones who taught me chaos theory.

I wasn't aware chaos theory dealt with quantum physics, but then I don't know much about it. And again, it depends what you mean by "random".

It would help if defined "deterministically chosen"and "determined outcome". To me, they mean there was no other choice or outcome for the mutation.

In reality, there WAS no other choice. From our point of view, it was random. The problem is, as I said above, there are two definitions of "random". Which one are we using, here ?

 

[Wowbagger]

For example, the decision to build that dam may ultimately depend on one person's opinion, and that opinion may very well be based on his mood the day that the paper has to be signed, and that mood may depend on the state of a brain cell within his brain, and that brain cell may be altered by the impact of a gamma ray, which was a quantum event that occurred when an atomic nucleus decayed inside the sun.

The next thing you are probably going to say is that a butterfly flapping its wings somewhere, could end up causing a hurricane somewhere else. The problem with that analogy, though, is that hurricanes are not determined by a single butterfly flutter, but by many, many other factors combined.
In your analogy, the person's mood is really the emergence of many brain cells, and is unlikely to change significantly, due to the impact of a gamma ray on a single brain cell.

A good counter argument I have heard is one of state-transitions: If changes in mood or storms are modeled in a similar way we model the states of matter (solid, liquid, gas, etc., etc.), a small change could be enough to decide which state the thing will slide into.

The counter argument for that counter argument is that transitional states are still possible: where the dam decision is neither pro nor con, where the storm is neither a hurricane nor a tropical storm, where matter is neither solid nor liquid; but in some realm in-between.

The counter to that counter counter is that the states in between tend to be unstable.

But, the final counter to those counters of the counter counters is: so what?! Probability is still reliable enough in the macro-world to make predictions. If that were not the case, there would be no such thing as science.

 

[Skeptic Ginger]

Don't be so picky. The point is it's a semantic argument, and pointless.

But if you insist: a Hawaiian and an Inuit are in New York on a spring day:

"It's cold!" "No, it's warm!" "No, it's cold!" "No, it's warm!" "No, it's cold!" ...

Happy now?

I think there is a tiny thread of truth to what you say, everyone looking at the same problem from a different angle and seeing a different solution. However, once I started reading mijo's position and looked into all that probability/stochastic mathematical modeling mijo was applying to the tiny random component of evolution, it became apparent that his mathematical model really did not apply to evolution mechanisms.

I started thinking about how a particular allele spread throughout the population. A random mutation occurs, the offspring inherit it, there can be additional mixing and so on. I was looking at the delta CCR5 also known as the CCR5 deletion. It has been shown to increase resistance to HIV by altering the surface protein which the HIV must bind to to enter the human white blood cell. At first it was thought to have been amplified a thousand or so years ago when it provided an advantage against yersinia pestis (the plague). Then it was hypothesized to actually have emerged 5,000 years ago and perhaps was amplified as it provided an advantage in resistance to small pox. But the latest research is showing the distribution is actually probably one of normal dissemination with no amplification.

So that did suggest that the acquisition of the CCR5 deletion was random. It arose spontaneously as a random mutation and was disseminated via inheritance. So I was now left with the question, why did that not make sense in terms of selection pressures making evolution non-random? And I then thought of the 6 billion different genomes give or take in the human population which all contained random variations in genetic code. Again, that makes no sense considering we are all still human, two legs, two eyes, same circulatory systems, muscular systems, and so on. Species are not evolving right and left from these random changes. Sometimes species remain stable for long periods of time. When species do evolve, they do so in single directions at a time. This is not suggestive of a random process.

While there is a pool of random genetic patterns within the human population, and there is a range of variation, albeit how narrow or wide that distribution of variation is is relative to what you are comparing it to, there are still so many consistencies within species, and so many consistencies in the directions evolution takes, random just does not describe the result.

In other words, random describes the input but not the output. The mathematical model mijo tries to apply because there is random input (though it turns out the input is a lot less random than we at first thought), does not in fact apply. In mijo's mathematical model and in the analogy Wayne used describing random numbers in meant random numbers out, the results of such a model were you to apply it in a computer program, would either fail to give you what evolution gives us, or it would give you (if you put the proper natural selection criteria in) predictable results. And random systems are not supposed to be predictable.

Mijo is taking a mathematical model which at first glance looks like evolutionary process, but upon closer testing, fails to describe evolutionary processes. The genetic mutations may indeed be random. But the processes of evolution take that pool of random nucleic acid substitutions and very specifically determines what is going to occur with those random genetic changes. So a better model is something akin to a random number generator that continually supplies numbers so that the ones you need when change is required will be in the pool. The random number generator is a tad inefficient, because it generates numbers you will never need and you have to continually clean those out, so to speak. But the benefit is the numbers you do need continually appear. That gives you a predictable supply of genetic code to meet the unpredictable circumstances that the organism may be faced with.

 

[mijopaalmc]

skpetigirl-

Did everyone who possessed the CCR5Δ32 mutation and was infected with the plague and smallpox survive and reproduce while everyone who possessed the CCR5Δ32 mutation and was infected with the plague and smallpox died without reproducing?

My is that the mere biasing of survival and reproduction does not make evolution non-random.

 

[mijopaalmc]

How is the model that skeptigirl claims I created not representative of evolution?

 

[Shoogar]

I noticed a random process that leads to a definite result everytime.

A tire had blown out on the interstate leaving shards of rubber everywhere. Everytime one of the pieces was run over it would randomly move, sometimes left and sometimes right. But eventually all the pieces end up off the roadway. An example of random events leading to a decidedly non-random conclusion.

 

[sol invictus]

The genetic mutations may indeed be random. But the processes of evolution take that pool of random nucleic acid substitutions and very specifically determines what is going to occur with those random genetic changes. So a better model is something akin to a random number generator that continually supplies numbers so that the ones you need when change is required will be in the pool. The random number generator is a tad inefficient, because it generates numbers you will never need and you have to continually clean those out, so to speak. But the benefit is the numbers you do need continually appear. That gives you a predictable supply of genetic code to meet the unpredictable circumstances that the organism may be faced with.

There is an interesting question one could ask. Suppose you went back to the time just after the first life had emerged, and you changed some small thing (the proverbial butterfly flapped its wings, or Homer Simpson sneezed). Three billion years later, what kind of life would be around?

Obviously no one knows the answer, but my intuition is that while complex life would have evolved, it would look quite different from us (at least superficially). That alternate skeptigirl might have ten arms, or none. Maybe we'd be born in pouches, or spread on the wind like dandelion seeds. So in that sense, evolution is random.

But on the other hand I think it's almost certain that complex (and probably intelligent) life of some sort would come to be, given enough time. In that sense evolution is deterministic.

This is what I meant to represent with my pinball analogy - the motion of the ball is unpredictable, and whether it drains down the middle or to the side is too, but it's inevitable that it will drain eventually.

 

[Meadmaker]

I wasn't aware chaos theory dealt with quantum physics, but then I don't know much about it. And again, it depends what you mean by "random".

The prof's point was that the unpredictability of a chaotic system is not just due to insufficient knowledge of the initial conditions. He spoke of systems where any uncertainty at all would lead to unpredictable final positions on a much larger scale. Then he noted that this was true right down to quantum level. Even if you knew the state of every particle down to the limits of the Heisenberg principle, you still wouldn't be able to predict the final state of the system.

On the other hand, if you simply were to answer some of the questions about the final state as, "You can't know, it's chaotic", you would fail the class. We spent time trying to characterize the range of possible final states. In most chaotic systems worth studying there are some states that are highly likely. There are other states that are absolutely impossible. One way, but only one way, to characterize systems might be to talk about the probability distribution of final states based on whatever is known about the initial state.

Evolution is a bit like that. We don't know how species will look in a million years. Furthermore, this is not just a limitation of our ability to measure initial conditions or compute equations of motion. Quantum effects will influence the future development of life. On the other hand, we can say that some developments are highly likely, while others are absolutely impossible.

Does that mean that evolution is random? I think it means that one sentence summaries of such a complex phenomenon are useless.

 

[Meadmaker]

This is what I meant to represent with my pinball analogy - the motion of the ball is unpredictable, and whether it drains down the middle or to the side is too, but it's inevitable that it will drain eventually.

The pinball analogy is a good one. Let's carry it a bit farther. If the final state of the ball is considered the final state of the system, it is deterministic. When it's done, the ball will be at the bottom of the board, waiting for the next quarter to give it new life.

On the other hand, what if we consider the final state of the sytem to be the position of the ball, plus the final score? Then, the final state has a random component.

Once again, whether we call the system "random", or not, depends on exactly what aspect of the system we are considering.

 

[Kotatsu]

I'm surprised no one has responded to this yet. Spiders typically have 8 eyes. I'm not aware of any other species with more than 2 eyes, but spiders definitely do have more.

If you by "species" do not limit yourself to arthropods, then sea stars and many kinds of flatworms have more than 2 eyes. I believe there are nematodes that have more as well, and maybe gnathostomulids, but I can't remember at the moment.

ETA:
Having read skeptigirl's post again, I can point out that there are also numerous groups of organisms which develop no eyes. For instance sponges, cnidarians and many of the smaller phyla.

I also assume that mijo is not interested in being given an example which, so far, complies with all his criteria, but is more interested in semantics and squabbling. I keep my examples to myself, then.

 

[mijopaalmc]

I also assume that mijo is not interested in being given an example which, so far, complies with all his criteria, but is more interested in semantics and squabbling. I keep my examples to myself, then.

I honestly don't see what you don't understand about My previous response. If an individual doesn't produce reproductively viable offspring (i.e., offspring that can themselves produce offspring) for any reason pertaining to its genetic makeup and/or how its genetic makeup mixes with others of its species, it fails to reproduce in the sense that I was trying to convey. Again, this is for any reason, regardless if whether the the offspring die during pre-natal development, can't find food or mates or escape predators as efficiently as others of its species, have gonads that don't produce functional gametes, or produce sterile offspring with other individuals of their species.

As far as notation goes, I think we need to agree on some standard notation because the scheme that I am using right now does not take into account the full complexity of the situation. As I see it, there is a collection of genes that are subject to non-neutral selection (the "selection complement") the variable expression of which lead to the observed phenotype of the individual. Thus, there are at least two ways in which two individuals can possess different phenotypes:

1. They can have selection complements with different alleles in them
2. They can have selection complements with identical alleles in them that are differently expressed

In my previous posts, I was talking about gross morphological characteristics (i.e., shape of beak or wingspan) but I was also trying to emphasize that such characteristics have and underlying genetic basis. However, I failed to express them unambiguously. I would therefore appreciate it if you helped develop some notation or referred me to some preexisting notation that captures the above two concepts so that we can have a discussion that is unambiguous as possible. I will then be able to explain what I mean more clearly.

 

[mijopaalmc]

Kotatsu-

The example to which you refer does not actually comply with all my criteria, because I was referring to the behavior of a population as an ensemble of phenotypes* not just a single phenotype as a collection of individuals. What I am trying to say is that, given a population consisting of phenotypes A, B, C, D, and E with numbers of individuals N_A, N_B, N_C, N_D, N_E, respectively, selection can be either be deterministic or stochastic. It is deterministic if the post-selection parental population consists of N_A+N_B+N_C, because all of the A, B, and C individuals survived while none of the D, and E individuals survived. It is stochastic if the post-selection parental population consists of 0N_A+.1N_B+.2N_C+.3N_D+.4N_E, because some of the B, C, D, and E individuals while others didn't, even if none of the A individuals survived.

*For now, phenotypes will be genetically distinct selection complements

 

[Belz...]

The prof's point was that the unpredictability of a chaotic system is not just due to insufficient knowledge of the initial conditions. He spoke of systems where any uncertainty at all would lead to unpredictable final positions on a much larger scale. Then he noted that this was true right down to quantum level. Even if you knew the state of every particle down to the limits of the Heisenberg principle, you still wouldn't be able to predict the final state of the system.

Hell, I'm not even sure quantum 'chaos' affects the macroscopic world in any way, so we're a far cry from saying that.

Evolution is a bit like that. We don't know how species will look in a million years. Furthermore, this is not just a limitation of our ability to measure initial conditions or compute equations of motion. Quantum effects will influence the future development of life.

Evidence ? Can quantum fluctuations knock a piece of your DNA out of place ?

 

[Kotatsu]

I honestly don't see what you don't understand about My previous response. If an individual doesn't produce reproductively viable offspring (i.e., offspring that can themselves produce offspring) for any reason pertaining to its genetic makeup and/or how its genetic makeup mixes with others of its species, it fails to reproduce in the sense that I was trying to convey. Again, this is for any reason, regardless if whether the the offspring die during pre-natal development, can't find food or mates or escape predators as efficiently as others of its species, have gonads that don't produce functional gametes, or produce sterile offspring with other individuals of their species.

I do understand your previous response. My further questions were posed to make sure that I had understood it correctly, and to clear away as many possible loop holes as possible. I am involved in another discussion on similar matters at the moment, and my counterpart there is making his best to obfuscating the matter by semantics, faked misunderstandings, ignorance and so on.

As to notation, the scheme you outlined in your subsequent post suffices for my needs, and may even be a bit over-elaborate.

My question to you is if polyploidisation in obligate sexuals would be an example worthy of discussion as a candidate for evidence against your assertion? It would consist of having a population with N members, which through one of many mechanisms would be able to assume the states A (diploidy), B (tetraploidy), C (8-ploidy), D (16-ploidy) and so on. Interbreeding between states A and any of the other may or may not work, but the offspring is (in the case AB) triploid, and thus usually infertile. If we limit ourselves --- as is most usual --- to just states A and B, we would then have a deterministic model: all individuals with state B will fail to have the possibility to get fertile offspring.

This assumes that polyploidisation is rare enough that two tetraploid individuals will never meet. I will elaborate more, if necessary, after I have read your response to this. Note that I don't want to state that I think this definitely is an example which

would settle this debate (i.e., whether all individuals with a given collection of phenotypes all reproduce while all other individuals with other phenotypes don't)

I am just curious to see if it is; you obviously know better than me what would and would not meet your criteria, and you have discussed this more thoroughly than I have. I just have the feeling that people most often overlook polyploidisation when they talk about evolution, possibly because if generally happens to icky animals.

 

[sol invictus]

Evidence ? Can quantum fluctuations knock a piece of your DNA out of place ?

Yes, absolutely.

Cosmic rays, which are individual highly energetic particles, can cause mutations or cancer by damaging DNA. Your risk of cancer is increased by flying in planes a lot, because the less atmosphere there is above you the more often you're hit by one.

Skin cancer can - and often is - caused by a single UV photon.

Radioactive materials produce various types of nasty particles which can cause cancer and mutations.

In all these examples the particles in question are produced by a single quantum event which is truly random (in the sense most people use that word) so far as modern science can say.

 

[Belz...]

Yes, absolutely.

Cosmic rays, which are individual highly energetic particles, can cause mutations or cancer by damaging DNA. Your risk of cancer is increased by flying in planes a lot, because the less atmosphere there is above you the more often you're hit by one.

Skin cancer can - and often is - caused by a single UV photon.

Radioactive materials produce various types of nasty particles which can cause cancer and mutations.

In all these examples the particles in question are produced by a single quantum event which is truly random (in the sense most people use that word) so far as modern science can say.

Huh ? Aren't those cosmic rays produced by supernovae ? Aren't those UV photons emitted by electrons ? How is that random ?

 

[Belz...]

I just have the feeling that people most often overlook polyploidisation when they talk about evolution, possibly because if generally happens to icky animals.

Who'd want to look at, or even think about, icky animals ? No, no, no. We prefer thinking about those cute, white baby seals that evil Canadians keep killing for their own twisted Nazi pleasure!

 

[Kotatsu]

Who'd want to look at, or even think about, icky animals ? No, no, no. We prefer thinking about those cute, white baby seals that evil Canadians keep killing for their own twisted Nazi pleasure!

I had one of my prejudices violated recently when I was presented with a stuffed toy in the shape of a louse (not Ischnocera that I work with, but an Anoplura, sadly, but you can't get everything...). Up until now I had believed that only cute animals were made into stuffed toys. Well, this particular louse is quite cute as a toy, but not in real life...

 

[sol invictus]

Huh ? Aren't those cosmic rays produced by supernovae ? Aren't those UV photons emitted by electrons ? How is that random ?

They're produced by quantum mechanical events. For example, take a molecule in an excited state at the surface of the sun. Every second, it has some probability to emit a UV photon. When it does, that photon could travel to the earth and cause a mutation in someone.

The process by which the photon is emitted (and by which it damages the DNA, for that matter) is quantum mechanical. In the most modern formulations of physics we have, it is a truly random, non-deterministic event. It cannot under any circumstances be predicted with certainty, no matter how much information you have or how precise your measurements are. The only thing we can speak about is the probability per unit time it will occur.

So everything in the world is affected - actually, determined - by truly random processes, including the orbit of the earth around the sun. One could therefore say that everything in the world is random, in that specific sense - but that is not a very useful statement, and in fact it's not even true if we use the most common definition of the word.

The motion of the earth around the sun is almost perfectly predictable, because all those random events add up to something that obeys very simple laws almost all the time. Therefore it shouldn't be called random. Whether or not the atom emits the photon in a given second is totally unpredictable, and should be called random. Evolution is somewhere in the gray area in between.