Perspectives on Evolution

[Gawdzilla Sama]

I started with these. I've given away a dozen copies of each since '08.

[Anomalocaris]

Evolution is one of the areas in science that bother me.  It's not that I don't believe in it-- in fact, I think evolution is a fundamental property of any system with complexity, bonded interactions, and time.

My problem is that when we talk about the evolution of a species, we are talking about a species as though it's a thing.  This strikes me as somewhat mythological: humans cannot evolve (except in a different sense intellectually perhaps), but what it means to be human is slowly shifting-- there's a kind of Archetypal Man who is changing over time, both genetically and memetically (if I can coin that term).


So what, exactly, is changing over time?  Nothing, in fact, is changing, at all, ever, in evolution, any more than colors change from red to blue in a rainbow.  Nothing is developed, and yet it obviously IS developed.

Think of a specie as a large collection of lights of different colors.   Most lights don’t change colors before they burnout.  But very few may contains a random defect and would change their color once before burning out. Every time a light burns out, there is a chance another one or more light of similar color to the color of the burnt out bulb replaces it.  

Now imagine the chance that a burnout bulk will be replaced depends on the color of the burnt out bulb.

Now you can see how over time, the average color of the total collection of the lights will change.


The individual lights don’t evolve.  They just come on, and burn out.  Maybe once in a great while something happens and a bulb changes color.  That’s not evolution,  that’s defect.

Evolution is when the average color of all the lights taken together gradually change over time.

[bennyboy]

I'm not sure exactly what you mean by 'humans cannot evolve'.  We are evolving.  Every organism is, all the time.  It might be hard to comprehend because our human timescales are less than a blink compared to the scales on which evolution works, but changes in allele frequency over time is absolutely happening in humans - and with enough time these changes in allele frequency leads to speciation.

Let me specify.  I mean that individual human beings do not evolve.  There are no physical objects in existence which are undergoing the process of evolution.

[Gawdzilla Sama]

I'm not sure exactly what you mean by 'humans cannot evolve'.  We are evolving.  Every organism is, all the time.  It might be hard to comprehend because our human timescales are less than a blink compared to the scales on which evolution works, but changes in allele frequency over time is absolutely happening in humans - and with enough time these changes in allele frequency leads to speciation.

Let me specify.  I mean that individual human beings do not evolve.  There are no physical objects in existence which are undergoing the process of evolution.

Oh boy. You need those books I posted.

[bennyboy]

Afaik evolution is not defined via species or speciation, but by changes of gene frequencies in a population. Speciation (splitting up of populations into groups that don't mate anymore) is a higher level outcome of that..?

Yeah even in my OP there's some conflation. To me, evolution is not really a process, but a statistical description of data sets in a context that has members which can interact, and in which different kinds of interactions can persist variably over time. But in talking about for example humans, it's fair to infer I'm also talking about speciation.

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Maybe it would help you to think of a persistent pattern that's changing. After all, you can't step into the same river twice because it contains different water molecules the second time. Even the shape of the river is changing slowly over time. Same with a cloud above a hill. The cells in our body get replaced over time as well. So the pattern that we call human is changing over time because of evolution.

Interesting. Would you describe the process of aging as a kind of evolutionary process? Certainly, the question "Who's aging" is something akin, since 5 year-old bennyboy never died, but clearly does not exist as he did. I think when you say pattern, it's much like the "Archetypal Man" I mentioned in the OP, it's more man-ness, than any individual man (or even collection of men).

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Yearp.  Changes in gene frequency over time is evolution, and evolution + a shit ton of time = speciation.

Is this really how evolution is defined? How would changes in gene frequency over time be measured? Certainly, very much or even most of the evolutionary narrative is based on fossils, no?

[SteveII]

I'm not sure exactly what you mean by 'humans cannot evolve'.  We are evolving.  Every organism is, all the time.  It might be hard to comprehend because our human timescales are less than a blink compared to the scales on which evolution works, but changes in allele frequency over time is absolutely happening in humans - and with enough time these changes in allele frequency leads to speciation.

Let me specify.  I mean that individual human beings do not evolve.  There are no physical objects in existence which are undergoing the process of evolution.

You are right. The biological evolutionary process requires natural selection and natural selection cannot happen within the lifetime of one organism.

[Anomalocaris]

Let me specify.  I mean that individual human beings do not evolve.  There are no physical objects in existence which are undergoing the process of evolution.

You are right. The biological evolutionary process requires natural selection and natural selection cannot happen within the lifetime of one organism.

No it could. If the organism lives past its reproductive succcess or failure.

[Thumpalumpacus]

Yearp.  Changes in gene frequency over time is evolution, and evolution + a shit ton of time = speciation.

Is this really how evolution is defined?

Yes, that is the definition of evolution I learnt in PhysAnthr101.

 

How would changes in gene frequency over time be measured?

Before modern technology, agrarians measured it very roughly by phenotype -- that is, the physical expression of the dominant genes in one's heredity. This is exactly how they genetically engineered animals such as domesticated cattle, or plants such as wheat or corn. The old MkI eyeball can see one hell of a lot of detail.

 

Certainly, very much or even most of the evolutionary narrative is based on fossils, no?

Not any more, not since the time of Mendel, and then Watson/Crick.

Definitely need to read up on this, Ben. The Modern Synthesis blends Darwin's original theory with Mendel's insights into genetics, and then a few decades after that happened Watson and Crick discovered the architecture of DNA and the exploration of its components started, which knowledge was then folded into the Modern Synthesis. Fossils are good clues, no doubt, but modern biochemistry is by far the more powerful tool for understanding evolution by natural selection.

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[...] natural selection cannot happen within the lifetime of one organism.

Selection happens depending on whether death occurs before or after reproduction, and whether death was caused or avoided by one or more mutations. The changes in alleles in a population -- the statistical changes which result in speciation -- take lifetimes. Do not confuse the two.

[Astonished]

Evolution is one of the areas in science that bother me.  It's not that I don't believe in it-- in fact, I think evolution is a fundamental property of any system with complexity, bonded interactions, and time.

My problem is that when we talk about the evolution of a species, we are talking about a species as though it's a thing.  This strikes me as somewhat mythological: humans cannot evolve (except in a different sense intellectually perhaps), but what it means to be human is slowly shifting-- there's a kind of Archetypal Man who is changing over time, both genetically and memetically (if I can coin that term).


So what, exactly, is changing over time?  Nothing, in fact, is changing, at all, ever, in evolution, any more than colors change from red to blue in a rainbow.  Nothing is developed, and yet it obviously IS developed.

You probably need to do a bit more reading on the subject. You are aware there are six-fingered persons, yes? So if some kind of viral plague came along and wiped out most everyone but for the few that have six fingers, eventually after generations of breeding, the dominant trait will be six fingers. A singular mutation can thrive and make humans noticeably different from the current majority, and humans are always mutating. There are some crazy number of mutations within the genetic code for each human born compared to the parents that spawned them, even if those genes don't express themselves (I think they call it junk DNA or something...just one of the things that makes nonsense of intelligent design). There's nothing saying that those genes can't someday express themselves with the right combination of mutations and there's no way of knowing just what form that expression will take.

So we're seeing evolution in humans all the time. There's a family that has nigh-unbreakable bones, a child born with some kind of extreme muscularity, and a few others. Just because it's not more widespread doesn't mean it's any different than the stuff happening throughout evolutionary history, we just haven't had enough time to see full-blown species change to where they're not just unable to breed together when separated (like the fruit fly experiments) but becoming entirely different, unrecognizable species. No one's going to see anything that extreme in our short lifetimes but there's more than enough evidence even without fossils, and even if we didn't understand genetics, we'd still have heredity to go on. Also consider the lifespans of other creatures; they'd probably breed a lot more, have more offspring per birth cycle, live shorter so they'd make more room for the new generations, and have more pressure to get to breeding what with the pre-civilized world. We live a long time, breed more infrequently (at least nothing compared to back before vaccines) and don't abandon the deformed ones to die like I think I heard some wolves or something do with their ugly offspring.

Also, is this really a topic for the philosophy section? Maybe life sciences would be a better place for it.

[bennyboy]

This is in fact meant for the philosophy section. I'm not doubting evolution, I'm talking about material, supervenience, emergence of properties, and that kind of thing-- interpretations of how to look at evolution, not about whether it is a scientific fact or not.

It's fine to say, "humanity evolves." But to me, this is a little circular-- if humans are defined as those organisms matching a particular phenotype (or certain genetic markers), and that phenotype or genetic makeup changes, then what does this really mean? Is humanity in fact evolving, or are more and more individuals diverging from the defining features of that species, until at some point it cannot be said to exist anymore?

What, exactly, is undergoing the process of evolution? Not genes. Not individual human organisms.