[QUOTE=Starving Artist]
I have no idea. 
It’s just that it’s always struck me in these threads vis-a-vis evolution that no one ever seems to talk about plant life and/or how it’s evolved.
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Dawkins’ The Ancestors’ Tale has some nice sections on the evolution of plant life and the things that came before the split. I’m sure there are better sources, that’s just the one I’ve read.
[QUOTE=vison]
I don’t see the various ethnic groups as “evolution”. Am I wrong?
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Evolution is just change over time. We probably all looked pretty much the same when we went through that evolutionary bottleneck, and it’s thought that physical differences we see in different human populations started to appear 15 or 20k years ago. So yes, that is evolution. However, it doesn’t mean that any particular population of humans is “more evolved” than any other. “More evolved” is a meaningless term.
[QUOTE=Starving Artist]
And then of course, we have not one life form spontaneously combusting, but two: animal & vegetable.
Nobody ever talks about plant life in these threads.
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First of all, there are not two but six accepted kingdoms in the domain of living organisms: Animalia (all multicellular animals), Plantae (multicellalar photosynthetic plants), Fungi (non-photosynthetic multi-cellular organisms that have cell walls), Archaea (simple and typically specialized bacteria-like organisms), Eubacteria (larger and typically more generalized single cell prokaryotic bacteria), and Protista (a grab back of simple single-cell or nonspecialized multicellular eukaryotic organisms). It is widely accepted that all organisms in these kingdoms are derived from a common ancestral progenote, and the study of molecular biology has reinforced this as a genetic structures are found across wide segments of the domain of terrestrial life. (All terrestrial life uses DNA as the encoding medium for the proteins and polysaccharides, and lipids which make up the bulk of most living organisms.)
As far as we are aware and all evidence indicates, life arose only once, and that everything considered to be “alive” today derives from a common source. (It is entirely likely that something like life has arisen on numerous occasions but that the original form readily outcompeted later pretenders.)
[QUOTE=panache45]
Why are you assuming all changes are small? Remember that girl in India who was born with four arms, not long ago? That’s a quantum leap over all her two-armed ancestors. If she had been allowed to mature with those arms, perhaps they would have become an evolutionary advantage. I can think of lots of circumstances in which we’d be better off with an additional arm or two. This could have been an example of evolution at work, in only one generation.
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No, that is a result of what is almost certainly developmental misfire, a problem during prenatal development that resulted in differentiating cells into limbs in the wrong place, or partial absorption of one developing fetus by another. It is a certainty that she would not have been developmentally mature (insofar as the human anatomy has no way to realistically accomodate a second set of arms) and very, very unlikely that this was the result of a viable genetic modification that could then be passed upon to successive generations. The sort of “quantum leap” that you propose is colloqually known by zoologists and evolutionary biologists as a “hopeful monster” and is widely considered to be not only fundamentally unlikely but also an example of the type of systemic or saltational mutation that, if true, would in fact be the sort of event that would support the notion of an Intelligent Designer (or some other, equally unlikely theory of transmission of desired or acquired characteristics), in lieu of some process that could be rationaly explained by natural selection. Instead, what we see in the fossil, genetic, and natural breeding records is modification via successive small changes repeated over generations. A hopeful monster, if such were found in nature, would not be evidence of modern evolutionary synthesis but a redupation of it.
[QUOTE=vison]
I don’t see the various ethnic groups as “evolution”. Am I wrong?
[/QUOTE]
Variation in phenotypes associated with geographical ethnicity is most certainly evolution in evidence. Admittedly, these adaptations don’t serve us particularly well today, but the incidence of sickle-cell anemia in humans of African ethnicities (providing protection against the malaria parasite) and the adult lactose tolerance of people in Northern Europe are but two of many examples of adaptation in modern humans. The physical phenotypes (light skin for more northern populations, darker hues toward equitoral regions) speak for themselves. Some cultural differences, like eye and hair color, may be entirely incidental but reinforced by allopatric diffentiation and eventually serve the incidental purpose of readily identifying outsiders.
Stranger
vision: Out of curiosity, how do you think the different ethnic groups got to look the way they do if not by evolution?
In Survival of the Sickest, Dr. Sharon Moalem proposes that much of evolution is an adaptation to some suddenly-developed environmental condition or disease, and points out that the stress of such conditions or diseases can either cause 1) a vastly increased rate of mutation, 2) previously “unused” genes to “switch on”, or both. The point here is that evolution is by no means a uniformly smooth process, and that much of it may occur in fits and starts. Fascinating book.
[QUOTE=John Mace]
vision: Out of curiosity, how do you think the different ethnic groups got to look the way they do if not by evolution?
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I phrased my comment very badly, I’m sorry. Of course it’s evolution! I meant that we are still all the same species, that the differences between groups of people are not significant. I was aiming at wondering, or asking the question, speculating: what might the human race become? When our descendants are a different species? How will they differ from us?
[QUOTE=vison]
I phrased my comment very badly, I’m sorry. Of course it’s evolution! I meant that we are still all the same species, that the differences between groups of people are not significant. I was aiming at wondering, or asking the question, speculating: what might the human race become? When our descendants are a different species? How will they differ from us?
[/QUOTE]
There is at least one theory that evolution will not continue in the human species, because we are self-aware and are interfering with natural selection. It seems to me this may not represent a cessation, but at least a change, though I’m not educated enough to even tell the difference.
And once we start widespread gene-therapy on humans, I don’t know what you’d call it.
And I suppose by these criteria, eveolution has ben either stopped or radically altered for any number of domesticated animal and agricultural crop species.
[QUOTE=Boyo Jim]
There is at least one theory that evolution will not continue in the human species, because we are self-aware and are interfering with natural selection. It seems to me this may not represent a cessation, but at least a change, though I’m not educated enough to even tell the difference.
And once we start widespread gene-therapy on humans, I don’t know what you’d call it.
And I suppose by these criteria, eveolution has ben either stopped or radically altered for any number of domesticated animal and agricultural crop species.
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Yes, I understand those points. But the world might look very different in 100 or 1,000 years - and not necessarily better, either. Our descendants might be very few, might be eking out a precarious existence due to some major collapse of our “civilization”. Or not, of course. And my imagination won’t take me 10,000 years, not at all.
Actually, we’re evolving faster and faster. Who’d have thought that?
[QUOTE=vison]
I phrased my comment very badly, I’m sorry. Of course it’s evolution! I meant that we are still all the same species, that the differences between groups of people are not significant. I was aiming at wondering, or asking the question, speculating: what might the human race become? When our descendants are a different species? How will they differ from us?
[/QUOTE]
Defining when a population becomes a different species is somewhat arbitrary, since you can’t figure out if organism separated by time can produce fertile offspring. Typically, though, it takes about 500k to 1M years for speciation to take place in large mammals like humans. However, if we’re still around 500k years from now, genetic engineering will most likely play a bigger role in changes of our genetics than natural selection will.
[QUOTE=Stranger On A Train]
First of all, there are not two but six accepted kingdoms in the domain of living organisms:
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That is sooo 1970s!
The most modern (1990+) analyses have focused on three Domains – Archaea, Bacteria and Eucaryota – each of which contain several Kingdoms.
Personally, I despise the whole ranking system anyway, so prefer to think of them all as simply “clades”.
Can they? Sure. Did they? Probably not. Not all features are adaptations in a given environment. As environments change, the relative adaptive value of traits changes. Some may go from detrimental or neutral to advantageous, others from advantageous or neutral to deleterious, and still others may go from selectively neutral to beneficial or disadvantageous.
[QUOTE=Dertulm]
Evolutionary theory inevitably requires large amounts of time, since the whole idea is that many small changes, when added together, result in very large changes, and the small changes have to happen sequentially, and each takes time. Fine and good, and I’m not arguing against the principle. Two questions arise, however:
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Major problem in the section I italicized. Some changes confer an advantage; some are a disadvantage; and some don’t matter one way or the way, but happen associated with traits in the first two categories. Hell, some traits offer an advantage under some circumstances but not others: consider sickle cell.
[QUOTE=brazil84]
Do plants have DNA and base pair coding similar to that of animals? I think so. If so, it again suggests a common ancestor.
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Not only is the base pair coding scheme identical between humans and plants, but the contents themselves are highly similar. This is sort of a layman’s measure so it’s difficult to find a proper scientific cite, but this article suggests that 60% of human DNA is also found in banana DNA. cite
I’m not clear what distinction you’re trying to make. Genes are information that describe how a sequence of amino acids is assembled together in a particular spatial arrangement to produce a protein. The starting material is nothing like the finished material except in specification. This is exactly like a blueprint, not really like a recipe at all.
At any rate, I would suggest we abandon this thread until the OP provides an indication that he has not done the same. It appears we’ve been the victim of yet another drive-by pot-stirring by a creationist who just wanted to test out some new material.
[QUOTE=WhyNot]
Oh! Yeah, I’ve noticed that too. Makes me think of Ellie in Jurassic Park, pointing out that plants have defenses and modes of attack and communication (through chemicals released in the soil or air, I’m not being woo-woo here) all of their own, and seeing growing formerly extinct plants blows her mind, but all anyone wants to talk about is the freakin’ dinosaurs! 
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i was focusing on Laura Dern’s legs in that movie. They were very nice.
[QUOTE=John Mace]
Defining when a population becomes a different species is somewhat arbitrary, since you can’t figure out if organism separated by time can produce fertile offspring. Typically, though, it takes about 500k to 1M years for speciation to take place in large mammals like humans. However, if we’re still around 500k years from now, genetic engineering will most likely play a bigger role in changes of our genetics than natural selection will.
[/QUOTE]
I think it will take much less than 500,000 years, given our ability to meddle - an ability that is likely to be greater as time passes. But. That’s not quite what I meant and I wish I could express it more clearly: what would constitute a “new species”, regardless of how it came about? I guess this thread isn’t the place for speculation.
[QUOTE=vison]
That’s not quite what I meant and I wish I could express it more clearly: what would constitute a “new species”, regardless of how it came about?
[/QUOTE]
Hard boundaries are an arbitrary human construct. Thinking about animals as groups of distinct and separably discrete species is a useful conceptual shorthand, but biology doesn’t really work like that when you get down to the nitty-gritty. Basically, when the natural world refuses to cooperate with our preconceived notions, it is we who must compromise, lest our conceptual biases lead us into error.
[QUOTE=Cervaise]
Hard boundaries are an arbitrary human construct. Thinking about animals as groups of distinct and separably discrete species is a useful conceptual shorthand, but biology doesn’t really work like that when you get down to the nitty-gritty. Basically, when the natural world refuses to cooperate with our preconceived notions, it is we who must compromise, lest our conceptual biases lead us into error.
[/QUOTE]
Having said that, there does exist a fairly serviceable shorthand of what a species is, one that is useful enough that it shouldn’t be simply hand-waved from the discussion just because it doesn’t cover 100% of cases. I’ll quote it from Wikipedia:
[QUOTE=vison]
I think it will take much less than 500,000 years, given our ability to meddle - an ability that is likely to be greater as time passes. But. That’s not quite what I meant and I wish I could express it more clearly: what would constitute a “new species”, regardless of how it came about? I guess this thread isn’t the place for speculation.
[/QUOTE]
Yeah, we’ll be changing our genome much sooner than 500k years hence, if we’re still around at the time.
As for defining a new species, the best way to do that would be to look at the past. H. sapiens is delineated from H. erectus (or whatever you want to call the pre-*sapiens *species) due to certain anatomical features where the two population do not overlap. These are mainly seen in the teeth and the skull (including the size of the braincase). But I suspect that future scientists will be hesitant to proclaim a new species as long as there is some continuity of knowledge and/or culture. It’s not like you can just suddenly declare that we’ve become a new species unless we’ve engineered that to be the case. Or, perhaps we migrate to some other planet and have all human life on earth wiped out.
My argument that 3.8 billion years is not enough time was based on a gut feeling and, even though I don’t think it’s wrong, I probably won’t have the ability to defend it, so I withdraw it from the discussion. However, responses jumped on the weakest link of my argument. Can we please move on to discussing, say, bacterial flagellum, or, if you prefer, present to me clear examples of the development of complex new features using evidence other than presumptions based on the fossil record?
[QUOTE=Mangetout]
Actually, let’s not ignore it - because this statement illustrates - I believe - a flaw in the way you’re thinking about it all.
On all those planets where this amazing coincidence didn’t happen, is it the case that there are people sitting around complaining that there hasn’t been enough time for them to come into existence? It is only possible to make the observation that ‘wow, everything seems just about right for me to be alive!’, in conditions where that is already true. So it’s not really an amazing coincidence at all.
[/QUOTE]
You’re describing the anthropomorphic principle, which is often used to counter creationist arguments involving fine tuning, or the extreme improbability of life spontaneously originating. The atheist argument usually makes the point that anything which occurs was actually a highly improbable outcome. For example, what are the odds that every molecule of air in the room will be in its current position? Almost infinitely small, right? So is there no value in pointing out the unlikelihood of a particular event? What if you instead ask: What are the odds that the molecules will be in positions such that my next breath will supply me with oxygen? Pretty good, close to 1:1, I suspect. So when the creationist argues that it is highly improbable that life would emerge, he has to be careful not to assume dependencies that aren’t really there. We can’t say that the odds of the random combination of all 26 amino acids (I forget the number and don’t feel like checking at the moment) being left handed is 2^26, and therefore the odds of life arising are at least that small, because who’s to say right-handed amino acids wouldn’t work? That would be inserting the bias of our current viewpoint. While I understand the trap that lies in using this type of reasoning, that does not mean the argument is fundamentally flawed. The theist simply needs to be careful not to include factors which are not true contingencies.
So is it possible to estimate a probability for life spontaneously arising, assuming ideal conditions (whatever those are)? To start with, it is very difficult to define what constitutes the minimum criteria for “life,” but it seems reasonable to me to use the simplest forms of life we can observe today as a starting point. That doesn’t mean there couldn’t be simpler life forms, but it’s useful to examine these organisms to determine what features are necessary to support life. In regards to even the simplest organisms having self-replicating DNA, I found point 5 interesting on this page from Science Week. Now, I’m certainly no scientist, but from what I’ve read about the makeup of the simplest self-replicating life forms we can observe today, to even use the word “simple” is a stretch. They have DNA with a genome containing several hundred genes, cell membranes, metabolism, and so on. It’s pretty clear that these structures could not have formed as-is from a blind combination of available proteins and amino acids, radiated or otherwise. There would have had to be simpler organisms capable of self-replication and metabolism, which in turn could lead to the current mechanism of DNA replication, without using natural selection, since the genetic mechanism for passing on traits would not yet be in place.
So, my point is that, anthropomorphic principle aside, it is possible to demonstrate the difficulty of life spontaneously arising, without knowing all the details of how such a thing might happen. For some more points in this regard, the following were interesting:
http://www.answersingenesis.org/docs/196.asp
http://creationwiki.org/index.php/(Talk.Or…redibly_complex
[QUOTE=Pochacco]
If the diversity of life did not arrive from a succession of changes, what alternate mechanism are you proposing? Are you suggesting that different life forms on Earth do not share a common ancestor?
[/QUOTE]
That is correct. I believe natural selection takes place and leads to incredible variety, but that an intelligent creator is responsible for progressively adding new features and functions (i.e., new complex sets of genetic instructions) throughout the history of life on the planet. In that case, whether or not evolution is an otherwise viable explanation is pretty much irrelevant, since any such intervention would be outside the bounds of a naturalistic definition of evolution.
Evolution is not related to how life appears, so let’s not talk about the odds of how or where the first life began.
Also, please provide an example of what you think are new genetic codes a creator introduced.
