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Author Topic:   How do you define the word Evolution?
caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


(2)
Message 88 of 936 (803515)
04-01-2017 7:41 AM
Reply to: Message 87 by CRR
04-01-2017 6:42 AM


Re: My definition
The definition from population genetics; a change in allele frequency in a population over time; is unsatisfactory because it focusses on only a part of the whole scope of evolution.
Having thought about this - I agree. This definition does cover a more limited scope than what we usually mean when we talk about evolution. I think most people would agree that something like the endosymbiosis of mitochondria and chloroplasts is part of what we understand by evolution - but this is not captured by the change of allele frequencies definition.
However, your definition:
Evolution is the theory that all the living forms in the world have arisen from a single source which itself arose naturally from an inorganic form.
is not very satisfactory; since it seems to me that nothing that you've included is entailed by what we mean when we talk about evolution. Your definition would mean that someone who argued for two independent origins of life; followed by evolution with natural selection; would be arguing against evolution; which is obviously wrong.
It seems to me that all we really mean when we say 'evolution' in the biological sense is 'how organisms change over time'. Everything else is either about the mechanisms of evolution; or specific events in natural history as we understand it. They aren't part of the definition.

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caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


Message 140 of 936 (804726)
04-12-2017 5:20 PM
Reply to: Message 124 by Faith
04-11-2017 10:08 PM


I see. Interesting. Of course it DOESN"T arise from mutations, the alternative forms of the genes are built in; and of course although natural selection is sometimes the cause of the elimination of some variations to favor others, it happens more often from the new gene frequencies brought about by the simple splitting of a population into two or more subpopulations, and especially in the smaller population, with reproductive isolation.
As pointed out on another thread, this is impossible within your model of history. Some genes have literally thousands of different alleles in the modern human population. One individual human can carry no more than two. If humanity originiated from two people; or from a few people after the flood, then mutation is required to account for existing genetic diversity.

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 Message 124 by Faith, posted 04-11-2017 10:08 PM Faith has replied

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caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


Message 232 of 936 (805165)
04-16-2017 11:13 AM
Reply to: Message 152 by Davidjay
04-13-2017 9:38 AM


Variation in humans is by the Lord for diversity etc.... it in no way means mutational change.
STOP twisting words, to suit your theory. STOP the double speak.
This is not a twisting of words. A change to a gene's is what a mutation is. If you don't like the word for some reason we can just call it 'gene change' instead.
If you want to opt for Dredge's unfalsifiable and unhelpful answer that gene change is all done by God, then fair enough, but the existence of gene change is not avoidable.

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caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


(4)
Message 233 of 936 (805167)
04-16-2017 11:51 AM
Reply to: Message 194 by Faith
04-14-2017 9:14 PM


Re: alleles/mutations?
HOWEVER, it really depends on whether they are viable alternatives that actually do something to further variation(...)
Well, they're clearly viable, because most living people possess them. And they further variation, since people are more varied than they would be if we were all genetically identical. I'm a little unclear what you mean here.
If what you're suggesting is that there is no adaptive change, so that all alleles except the original Adam and Eve ones are functionally equivalent or harmful, well that's easy to disprove. We've already found funtional genetic variation in humans. To take an easy example (since I only know easy ones!) the gene EGLN1 exists in more than 300 different known variants in humans. EGLN1 produces a protein which is involved in response to low oxygen conditions. Certain rare variants of EGLN1 are very common among Tibetans, and they play a role in making these people better able to survive in the low oxygen environment of the Tibetan plateau. Different rare variants exist at high frequencies among Andean Indians, for the same reason.

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caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


(2)
Message 278 of 936 (805311)
04-17-2017 2:03 PM
Reply to: Message 234 by Faith
04-16-2017 5:11 PM


Re: alleles/mutations?
Yes a hundred or more new ones in every generation I understand? A few of which get passed on to the next generation. But that doesn't make them viable alternatives that further variation, since most of them are "neutral" which really means only slightly deleterious, not at a level to be weeded out by natural selection..
Clearly we're using these words in different ways. 'Viable' means 'capable of living and reproducing'. If organisms are living and reproducing with certain alleles, then these can make viable organisms.
As for furthering variation, this seems tautological. If generation 1 has alleles A and B, to which mutation adds a third allele C in the following generation, then generation 2 has more variation. I'm not entirely clear what alternative you're proposing.
You need to show 1) that these are actually mutations and not naturally occurring variants
We just covered that a minute ago. There are hundreds of known alleles of this gene. Adam and Eve can have had at most four.
and 2) if mutations, you need to show that all the variants actually DO something, since most mutations are neutral, not affecting the organism, to mildly deleterious, accumulating over time toward something undesirable.
Well that's why I chose this example, as it's one where we do have clear evidence that these variants are doing something - sorry if that wasn't clear. Some of the variants common amongst Tibetans have been demonstrated to protect against health problems associated with high altitude. Some lead to the production of more red blood cells; others have more complicated mechanisms that are a bit beyond my understanding of biochemistry (since overproduction of red blood cells can carry its own problems) - an example here if you wanted to have a look.

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caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


(2)
Message 296 of 936 (805441)
04-18-2017 1:41 PM
Reply to: Message 279 by Faith
04-17-2017 3:50 PM


Re: alleles/mutations?
Sorry if I'm not being clear, not sure exactly what this is about.
The hundred I mentioned aren't "viable" then, occurring in individuals where they can't be passed on, but supposedly might do something undesirable in the person's body?
The idea is that most of the mutations are in the individual's body but don't get passed on, those mutations we are all said to accumulate, most of which don't get passed on.
Yes, most mutations do not get passed on; since only those that happen in a germ-line cell (ie. a sperm or an egg) can be passed to a child. A mutation that happens in a skin cell of your arm is not important for evolution (this is true of something like a human, anyway - some other organisms (like many plants) can reproduce vegetatively as well and pass on pretty much any mutation).
The 'hundred or more' you mention, however, are I think supposed to be germ-line mutations - those which are passed on to children. The figure in humans is now believed to be lower; however - about 60 (this is based on direct comparisons between parents and children now that they're able to sequence whole genomes).
The question is what each of those alleles actually does. I accept that there are all these variations in the sequence, defining them as different alleles, but what exactly do they DO? How many of them just do what lots of others also do? We're talking about different versions of a particular gene, right? Presumably different versions, diffrerent alleles, exist to vary what the gene produces. If it's a gene for hair color one allele may be for brown, another for black, another for red and so on. If you have hundreds of such alleles, what does each of them do? In other words, why would more than four in a population be useful anyway? Especially when there may be a number of genes for the same trait that also have different alleles/versions, that combine with the other genes toward a particular effect in the organism.
Well, they won't all be useful variants. A lot of variation is selectively neutral, as you pointed out before. And of course unhelpful mutations can also be passed on. The only mutations which will be instantly removed by selection in every case are the dramatically deleterious ones. The mutations which cause the foetus to miscarry in the womb, or which make you certain to die in childhood, or which make you sterile; a mutation which is more subtly disadvantageous should be expected to lose out in the long term; but the term can sometimes be very long.
This raises all kinds of questions in my mind. How can such "mutations" really be mutations if they specifically and pointedly do things that are SO beneficial to the people in this situation? How do they get selected?
But as just pointed out, there are hundreds of known mutations (in this one gene). There are undoubtedly more that we haven't found - plus all those that were selected away or happened to die out. Most of them probably don't do anything beneficial to anyone. We're just looking at the few specific ones that are known to do something useful because that's what we were talking about.
As for how they get selected; surely this is something you understand already. People have been living on the Tibetan plateau for tens of thousands of years (though I know you don't accept the dating). People prone to altitude sickness are going to be at a disadvantage over people who aren't; especially in the hard times - when there is plague, famines, invasions, etc; and so over the long haul the variants which protect from altitude sickness will become more common.
This is not an instant process. This study identified a specific protective ELGN1 variant which is much more common in Tibet than anywhere else; but it's frequency in Tibet is at about 70%.
Even if what selection does is merely favor the reproduction of the best equipped/fittest individuals wouldn't getting such capacities established throughout the population cost an awful lot of (way too many) losses on the way to getting them established?
There's no threshold of acceptable loss - what would 'too many' be?
But I think you're thinking about it wrong. Imagine a situation where there are two organisms, but only enough food for one. The one who gets the food will live and reproduce, the other will starve. Now, if one has some advantage over the other (being faster, stronger, more persistent, whatever), and the advantage is genetically based, this one is more likely to get the food and survive, and its genetic advantage is likely to be passed on.
If the two are genetically identical, then one of them will still die anyway. In the first case there's selection, in the latter case not, but there's no difference in the loss to the population.
ABE: BUT, there is still the question how you know they are mutations anyway, as opposed to built in variations that simply accumulate, just as the mutations would supposedly do. How do you know the SOURCE of the alleles?
I'm not sure I understand this question. How can something accumulate if it's already built in? We know that a diploid population which starts with only two individuals can only have a maximum of 4 versions of each gene. If we find more than four versions in a later generation; then something changed.

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caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


(1)
Message 412 of 936 (806073)
04-22-2017 5:05 PM
Reply to: Message 378 by dwise1
04-21-2017 10:24 AM


Re: An Alternative consistent and coherent model
Common sense says that when it drops off the end it will continue to move in a spiral trajectory. It doesn't!
I did a bit of asking around to see if I was just strange, and have been unable to find anyone who would expect the ball to continue in a spiral path. I understand my methods are not rigorous; but I'm very curious about how the original study that is supposed to have revealed this was stuctured.
I can find literally no one who would expect the ball to continue in a spiral path. That's not common sense. That's contrary to everyday experience.

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caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


(2)
Message 860 of 936 (813681)
06-29-2017 4:23 PM
Reply to: Message 858 by Faith
06-29-2017 1:22 PM


Re: Polyploidy -- evolution by doubling the genome
This is not the story that has been told about these mice before this. If there is no intense selection pressure then of course you're not going to lose the alleles for the other colors. That happens with intense selection pressure.
The story has not changed; you may just have misunderstood it before.
The animal is question is Chaetodipus intermedius. The image below is from Nature. Most Ch. intermedius are the same colour as the light brown in upper left and lower right.
A few, however, are darker colours like the other two in the image. These darker coloured ones live in parts of the Sonoran desert with dark black rocks from prehistoric volcanic eruptions. These dark areas are separated from one another. Dark and light mice freely interbreed.
The reason we only find dark mice in the areas with volcanic rocks is natural selection - this is your reduction of genetic diversity. Lighter coloured mice get eaten more often on the volcanic rocks; and darker coloured mice get eaten more often elsewhere. The reason the different alleles are not eliminated from the global population of Ch. intermedius is that the selection pressures are different in different places.
The reason Taq is so inordinately fond of these mice as an example of evolution, though, is that there is not one allele for dark colouration. Every isolated 'island' of volcanic rocks seems to have a different allele for producing black fur. Once this allele arises, natural selection maintains it in the area with the dark rocks; but prevents it from spreading to other places where it would be beneficial - since no mouse can carry the gene except across the sandy-brown desert.
This does not look like your preferred pattern of two ancestral mc1r alleles differentially expressed in different populations; with mutated forms that either do nothing or are detrimental. Instead, we see different mutated forms becoming dominant in different areas of black rocks where they're beneficial - whichever one happened to arise first.

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caffeine
Member (Idle past 1024 days)
Posts: 1800
From: Prague, Czech Republic
Joined: 10-22-2008


Message 924 of 936 (814354)
07-07-2017 1:53 PM
Reply to: Message 916 by RAZD
07-05-2017 1:26 PM


Re: Polyploidy -- evolution by doubling the genome
And ... black is dominant ... so, the Hardy-Weinberg equation gives us:
The alleles should only be expected to be in Hardy-Weinberg equilibrium in the absence of selection. Since both phenotypes are under selection, it's not relevant. The proportions will depend on the extent of the habitats that select for each colour morph.

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