Evolution by Elimination - The Game

[Speedwell]

Thanks. It does seem to me the capability to mate is the only viable means of defining a "species". There's an odd interplay here where the definition of evolution involves populations, but DNA is organism specific. As such, reductio ad absurdum makes it nearly impossible to set how much difference in DNA (or morphology) constitutes a different species.

Certainly species determination is often difficult and sometimes controversial. The standard definition is that a population constitutes a different species when it can no longer interbreed with the parent species, but there will be an extended period of time when partial interfertility persists. If you are looking for a qualitative change during speciation you won't find one.

 

[essentialsaltes]

Thanks. It does seem to me the capability to mate is the only viable means of defining a "species". There's an odd interplay here where the definition of evolution involves populations, but DNA is organism specific. As such, reductio ad absurdum makes it nearly impossible to set how much difference in DNA (or morphology) constitutes a different species.

I don't understand what you're trying to say. You seem to agree about what a species means. So that's not controversial. That's all it takes for interbreeding to be theoretically possible. But if interbreeding is practically impossible because of geographical separation, that's what divides a species into separate populations.

The geographic area seems more to me a matter of practicality than rigorous definition.

Probably so. A population is a subset of a species that is geographically separated to some extent with any other populations of that species. Like say, sequoias in California that live in a few distinct 'islands'. While pollen from one island might get to another and cause 'mixing' this is a rare enough event that biologically, these different populations are considered distinct, even if they are not perfectly distinct. And what to do with those single dots, single trees or stands? are they separate populations, or just lumped into the closest decent sized island? Or just not considered, since they are too small to be of statistical significance. It's a matter of practicality rather than rigorous.

If that's not the case, I would say the definition is seriously flawed and would need to consider the allele frequency of all living things.

Why is that needed if we agree on what a species is?

Sure, but that hasn't entered the scenario yet as a consideration.

Just because you haven't mentioned it doesn't mean that mutations haven't entered the scenario by being past events that may have an effect on future outcomes.

A dog eats a poisoned ham sandwich and survives; this may be due to its particular alleles/mutations.

"I get in a car accident and survive."

Maybe that's due to the airbag.

"The airbag hasn't entered the scenario yet"

Well, you haven't mentioned it, but I can see that it entered the cabin of your car and saved your butt.

 

[Resha Caner]

I don't understand what you're trying to say. You seem to agree about what a species means. So that's not controversial. That's all it takes for interbreeding to be theoretically possible. But if interbreeding is practically impossible because of geographical separation, that's what divides a species into separate populations.

There are issues of confidence and induction at play here. So, let's take the color of the dog's fur as an example. Whether it's one or many allele's that determine fur color, I will simply refer to it as the "fur color allele" (FCA).

Within dog specimen A, FCA is located at position X in the DNA sequence. When we check specimen B, we again look in location X. But location X is not determined by counting exactly 1352647 positions down the chain. It's based on finding the gene starting sequence (TCG or whatever it is). Even then, the FCA in specimen B won't necessarily be the exact same sequence as it was in specimen A. There will likely be some variation.

So do we test the FCA in every specimen to absolutely confirm it really is the FCA, or do we conclude it is the FCA based on some confidence level of location and sequence? Let me know if I got something wrong there, but we're taking a sequence from an organism and projecting that onto a measure for the population based on some confidence level. Right? I'm not saying that's bad science, but you and I both know how tricky that can be. It's not as easy as it sounds when you read about it in a textbook.

Further, we're making inductive conclusions about what that population is. I'll sample this organism because, based on morphology, it looks like a dog. My specific example tells me this particular DNA sequence produces this morphology, so I'll extrapolate that to all similar morphologies in this geographic area. Or, if not that, I doubt I'm forcing all organisms in the population to mate to prove absolutely they fit the definition of species. And there are probably other inductions as well. Again, not bad science, but not guaranteed protection against misleading results either.

That's what my comment referred to.

Just because you haven't mentioned it doesn't mean that mutations haven't entered the scenario by being past events that may have an effect on future outcomes.

True, but it is improper to assume a cause until the conditions of the problem are given. Even if science has only found one cause for a given result, it is improper to assume that cause until the conditions are stated. Maybe it's just a technicality, but it's an important one for this conversation.

- - -

... Ben Franklin is still waiting for the storm.

 

[essentialsaltes]

There are issues of confidence and induction at play here. So, let's take the color of the dog's fur as an example. Whether it's one or many allele's that determine fur color, I will simply refer to it as the "fur color allele" (FCA).

Within dog specimen A, FCA is located at position X in the DNA sequence. When we check specimen B, we again look in location X. But location X is not determined by counting exactly 1352647 positions down the chain. It's based on finding the gene starting sequence (TCG or whatever it is). Even then, the FCA in specimen B won't necessarily be the exact same sequence as it was in specimen A. There will likely be some variation.

Alleles are different variations of a particular gene. If we identify the fur color gene (furc), we find that it comes it multiple alleles. Fluffy may have allele A, but Mutt has allele B. But both are of the same gene. If they aren't the same sequence, then they are NOT the same allele, they are different alleles of the same gene.

So do we test the FCA in every specimen to absolutely confirm it really is the FCA, or do we conclude it is the FCA based on some confidence level of location and sequence? Let me know if I got something wrong there, but we're taking a sequence from an organism and projecting that onto a measure for the population based on some confidence level.

I think something's wrong. We identify genes by what they do, like maybe make a protein, like tyrosinase, which regulates the production of melanin and consequently skin color. Everybody's got different alleles of that gene, and there are even alleles that result in the production of no melanin at all. This does not mean that their allele is not a 'skin color' gene. It is.

All of this was settled before we even knew what DNA was. But yes, genes are typically found at the same locus on chromosome whatsit. For instance "The location of OCA1 may be written as "11q1.4-q2.1", meaning it is on chromosome 11, long arm, somewhere in the range of band 1, sub-band 4, and band 2, sub-band 1."

Further, we're making inductive conclusions about what that population is. I'll sample this organism because, based on morphology, it looks like a dog. My specific example tells me this particular DNA sequence produces this morphology, so I'll extrapolate that to all similar morphologies in this geographic area.

If we measure a brown dog and find a particular DNA sequence of the fur gene, we do not conclude (or extrapolate) that all brown dogs have that sequence. There are lots of neutral mutations/variations of a gene that will produce the same phenotype. Nor do we conclude or extrapolate that all dogs with that sequence will be brown, since other regulator genes may play a role (as with albinism, where a perfectly functional melanin gene may be overridden by the different tyrosinase allele).

Or, if not that, I doubt I'm forcing all organisms in the population to mate to prove absolutely they fit the definition of species. And there are probably other inductions as well.

Yes, we make the bold assumption that all of the dogs are dogs (and of the same species). (I mean, you just poisoned a few dogs, you haven't seen any of them mate. Mating has not entered the scenario.)

 

[Resha Caner]

If we measure a brown dog and find a particular DNA sequence of the fur gene, we do not conclude (or extrapolate) that all brown dogs have that sequence.

I didn't mean to imply that.

I think something's wrong.

If I didn't lay out the example properly, I'm open to correction.

Everybody's got different alleles of that gene ...

Yes, I know. That was my point. So, when someone counts allele frequency they ... (fill in the blank).

But yes, genes are typically found at the same locus on chromosome whatsit.

I thought this was used to locate the alleles. I didn't think samples were taken by watching to see what that allele does in every organism. But, feel free to correct me.

In the end, it doesn't matter for my purposes in this thread. It was a tangent comment.

 

[essentialsaltes]

I didn't think samples were taken by watching to see what that allele does in every organism. But, feel free to correct me.

If I'm understanding you, isn't that what Mendel did (in the pre-DNA world) of looking to see whether peas were smooth or wrinkly?

I mean, the theory of evolution, genetics, and alleles all predate the discovery of DNA.

 

[Resha Caner]

If I'm understanding you, isn't that what Mendel did (in the pre-DNA world) of looking to see whether peas were smooth or wrinkly?

You could be right. I don't know. I assumed at least sometimes there was an attempt to confirm actual existence in the DNA. What you're saying is there is an assumption that we can determine allele frequency by observing the expression of traits.

Maybe. It just seems that could be confounded with phenotype, epigenetics, etc.

 

[drjean]

So if "improvement" is not part of evolution (natural selection implies a casting off of unnecessary and adding on of improving necessary) then why would "change" be considered "mutation"? Again, no.

 

[Tayla]

Is this evolution?

Evolution means mutations or gene copy errors which are passed on to subsequent generations because natural selection favors them. Ham sandwiches can't evolve because they are not biological organisms.

 

[Resha Caner]

@Speedwell , @drjean , @jesus316 : Thanks for the answers. I don't know everyone's background, so if any of you are biologists, I'd appreciate a comment on the exchange shown below. I mean, I do know some here (like @PsychoSarah ) have a background in biology, but she's not participated so far.

I think (not being a biologist) when we talk about allele frequencies changing over time, we're thinking about over generations.

Is there a formal definition of evolution that stipulates generations, or is that an informal understanding?

 

[essentialsaltes]

@Speedwell , @drjean , @jesus316 : Thanks for the answers. I don't know everyone's background, so if any of you are biologists, I'd appreciate a comment on the exchange shown below. I mean, I do know some here (like @PsychoSarah ) have a background in biology, but she's not participated so far.

Just trying to help.

From Nature:

"The study of evolution can be performed on different scales. Microevolution reflects changes in DNA sequences and allele frequencies within a species over time. These changes may be due to mutations, which can introduce new alleles into a population. In addition, new alleles can be introduced in a population by gene flow, which occurs during breeding between two populations that carry unique alleles. In contrast with microevolution, macroevolution reflects large-scale changes at the species level, which result from the accumulation of numerous small changes on the microevolutionary scale. An example of macroevolution is the evolution of a new species."

Both of the examples of causes of allele changes involve things that occur with the passage of genes across generations.

 

[Doctor.Sphinx]

I like your reply simply for the human element of it. I often get a sense that evolution is viewed as something that happens in "nature" apart from human interaction, and that any changes prompted by human interaction are interference. It seems more appropriate to say that whatever humans might do, it is merely one of many selective pressures. It also raises an interesting question about "life". If a living being actively pursues the proliferation of ham sandwiches, in what way is that different from the proliferation of life? I'm probably getting too philosophical.

You obviously have not read my book, the Blind Sandwich Maker, which does away with any superstitious notions of an intelligent or seeing sandwich maker. No, the blind sandwich maker is just a combination of economic factors and cost pressures which give the appearance of a sandwich maker to the ignorant and misinformed, which I am not. So the boring and less tasty ham sandwich will stop being produced for the delicious and appetising ham sandwich with mayonnaise, irrespective of any act of intelligence. This is all due to economic forces and the limitations of cash.

 

[drjean]

That the sandwiches do not make themselves, I find, is telling.

 

[Resha Caner]

Just trying to help.

Sure. Thanks.

 

[PsychoSarah]

@Speedwell , @drjean , @jesus316 : Thanks for the answers. I don't know everyone's background, so if any of you are biologists, I'd appreciate a comment on the exchange shown below. I mean, I do know some here (like @PsychoSarah ) have a background in biology, but she's not participated so far.

-_- ham sandwiches are not alive. It wouldn't matter how much you add onto the ham or even mess with the DNA that remains in the ham cells, those cells are dead and cannot reproduce. Furthermore, even if the ham sandwich was alive and capable of reproduction and the mustard somehow influenced the DNA, that'd be an example of mutation. Said mutations could lead to trends within the population of this hypothetical nightmare of living sandwiches, depending on how they reproduce and how well they repair damage to their DNA, and thus influence evolution, but would not be in and of itself "evolution".

This thread is very silly, I like it.

 

[doubtingmerle]

-_- ham sandwiches are not alive. It wouldn't matter how much you add onto the ham or even mess with the DNA that remains in the ham cells, those cells are dead and cannot reproduce. Furthermore, even if the ham sandwich was alive and capable of reproduction and the mustard somehow influenced the DNA, that'd be an example of mutation. Said mutations could lead to trends within the population of this hypothetical nightmare of living sandwiches, depending on how they reproduce and how well they repair damage to their DNA, and thus influence evolution, but would not be in and of itself "evolution".

This thread is very silly, I like it.

We are back to teaching basics. Cats have babies. Ham sandwiches don't. watches dont. Cars don't. But cats and dogs do. You would think it would be easy to get people to understand that.

 

[bhsmte]

We are back to teaching basics. Cats have babies. Ham sandwiches don't. watches dont. Cars don't. But cats and dogs do. You would think it would be easy to get people to understand that.

You would think yes. Some folks though, have other personal motivations.

 

[Ophiolite]

Is there a formal definition of evolution that stipulates generations, or is that an informal understanding?

The definition of evolution has itself evolved. If it seems vague to you, this is because the definition will depend somewhat upon context and perspective.

Here is an example: my field experience of evolution is almost entirely related to fossils. In palaeontology we cannot determine what alleles are present (though we can often make sound inferences), so any definition relating to alleles is meaningless in this context. For a palaeontologist evolution is evidenced by significant changes in morphology.

What constitutes a significant change? That's reasonably easy to define and difficult to detect. A significant change is one that goes beyond the boundaries of variation of the prior population. Now, if you've been paying attention to what others have been saying, you should be sitting up round about now and calling "foul". You have been told, by geneticists (or biologists in general), that any change in the proportion of alleles in a population is evolution. That's true. That's microevolution. That's what, for the most part, geneticists study. That's their limit.

Palaeontologists cannot work at that level of granularity. Palaeontologists focus on how those small, microevolutionary steps build up to macroevolutioary changes, detectable in the fossil record.

I hope that clarifies rather than confuses, but if it is the latter please feel free to ask any questions.

Note: I have responded to your quoted post without completing reading of the thread, so my remakrs may seem to ignore later comments.

 

[Resha Caner]

This thread is very silly, I like it.

Thanks. There are some further examples that build toward something a little more reasonable.

The definition of evolution has itself evolved. If it seems vague to you, this is because the definition will depend somewhat upon context and perspective.

... For a palaeontologist evolution is evidenced by significant changes in morphology ...

Thanks for some very interesting & enlightening comments.

All the comments have more or less reinforced my prior conclusions. I'm curious about a whole host of issues surrounding the topic of evolution. One of them involves the word itself. It has become so politicized that it seems to have become divorced from the issues. In other words, it seems to me certain segments of people are so violently opposed to the word evolution, that even if it's meaning were to drift toward "God's mysterious and special creation" they would still object. In other words, even if science were to find new mechanisms as the cause of life's diversity, and those mechanisms didn't cause any theological issues, some people would still object.

On the flip side, it seems evolution is now defined in such a way - with a broadness and informalness - that it can pretty much encompass anything related to change within a biological system. So, even if someone were to find an alternative explanation for the diversity of life and the means by which viable organisms form, biologists would absorb that idea and continue to use the term "evolution" to describe it.

For me both of those conditions are a bit frustrating, but I guess that's the way it is.

 

[Ophiolite]

All the comments have more or less reinforced my prior conclusions. I'm curious about a whole host of issues surrounding the topic of evolution. One of them involves the word itself. It has become so politicized that it seems to have become divorced from the issues. In other words, it seems to me certain segments of people are so violently opposed to the word evolution, that even if it's meaning were to drift toward "God's mysterious and special creation" they would still object. In other words, even if science were to find new mechanisms as the cause of life's diversity, and those mechanisms didn't cause any theological issues, some people would still object.

It should be straightforward to determine the intended meaning of evolution from context. For example:

At this point in the proto-stars evolution it enters the T-Tauri phase.

Evolution of graptolites in the early Silurian facilitates correlation of widely separated sedimentary sequences.

Ideas about the role of fire teams in the infantry evolved rapidly in WWII.

He has certainly evolved from the unruly teenager to his present status as a community leader.

Unfortunately, as you noted, there are some who choose not to make the necessary distinctions. For some this may be ignorance, for others it is deliberate obfuscation intended to support their agenda. This may be important from a theological standpoint and from the interaction of religion and science, but is has no bearing whatsoever on the practice of biology and development (evolution ) of evolutionary theory.

On the flip side, it seems evolution is now defined in such a way - with a broadness and informalness - that it can pretty much encompass anything related to change within a biological system. So, even if someone were to find an alternative explanation for the diversity of life and the means by which viable organisms form, biologists would absorb that idea and continue to use the term "evolution" to describe it..

No. This is absolutely not the case. There are many changes in biological systems that are not evolution. A complete list would probably fill a book, but here are a handful of very general examples:

• The changes that occur during the development of a fetus.
• The changes that occur during germination of seeds.
• The changes occur during mitosis.
• The changes to behaviour that occur during penguin mating season.

The definitions may be confusing and appear general, but the bottom line is that evolution is a permanent and heritable change in the genetics of an organism that will be reflected in its morphology or behaviour.