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Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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Author | Topic: Human - Chimp split 4 million years ago? | |||||||||||||||||||||||||||
RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Study moves chimp-human split to 4 million years ago
quote: From PLoS link:
quote: That would put australopithicus very close to the split. This is still a mathematical model of split time based on some kind of uniform rates of mutation ... or at best an average rate. I'm not sure that such models are valid for periods of speciation, when there can be more impetus for divergence to reduce direct competition. Enjoy ps - Human Origins forum ... compare Fiocruz Genome and fight Muscular Dystrophy with Team EvC! (click) we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share.
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AdminNosy Administrator Posts: 4754 From: Vancouver, BC, Canada Joined: |
Thread moved here from the Proposed New Topics forum.
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ramoss Member (Idle past 612 days) Posts: 3228 Joined: |
Just how well established is the model for a 'genetic clock' for mutations to begin with? I know it is an assumption, but what kind of evidence do we have that backs up that mutations happen at a measurable rate. Does this take into account changes in life expectancy?? How does this 'mutation clock' actually work?
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Just how well established is the model for a 'genetic clock' for mutations to begin with? The problem is: how do you baseline it? You can measure current rates of mutation and then assume that the rate stays constant (we wouldn't have a baseline long enough to do otherwise), but then you need some kind of measure of how many get fixed in the population - that's going to be another estimate (one I have some trouble with as we know that selection pressure can change this), and it is also going to be some rather uniform or average rate (due to lack of model for rate change or data to base one on that is more than a few years long). What they apparently did on this study was to use an 'accepted' age of the orangutan split as a baseline:
quote: So this is based on an average rate of mutation fixing in the orangutan line applied to the gorilla-chimp-human lineage. The problem I have is that we also have some evidence that the human lineage has more fixed genes than the chimp lineage: http://www.newsroom.ucr.edu/cgi-bin/display.cgi?id=875
quote: And having a different number of fixed genes also means a different rate of fixing genes - if we assume mutations average out to a relatively constant rate. A different rate of fixing genes makes sense because there are several different selection processes going on, processes that necessarily run at different rates: genetic drift, survival selection and sexual selection. The relative importance of each process can shift depending on circumstances and behavior patterns.
(Note - Personally I think the reason for the higher human rate is sexual selection - if not runaway sexual selection - with the evidence being the apparent skin bareness, extremely long head hair, and a creative brain that increased in size until it endangers the life of the mother and child at birth - it's maxed out.) So if we know that two branches have evolved at a different rate of fixing genes how can we assume a same or average rate anywhere else without it being suspect? It seems to me that these genetic clock studies are looking at the data from the wrong viewpoint. Rather than looking at the data and trying to develop an age from common ancestor based on assumed rates of mutation they should be looking at the data with all the current best fossil dating evidence for age from each common ancestor and be looking at what that means for the rate of fixing mutations in those populations. That would be information worth knowing. Enjoy. Edited by RAZD, : subtitle compare Fiocruz Genome and fight Muscular Dystrophy with Team EvC! (click) we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share.
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jbuchanan Junior Member (Idle past 6232 days) Posts: 1 Joined: |
Hi, I am someone who is both inquisitive and skeptical of Darwinian descent with modification. One of the main reasons I have always been a skeptic of Darwinism is not necessarily because of the evidence,but rather the mechanism, which is often overlooked and dismissed as a given when discussing the evolution of life.
Darwinists contend that humans and all life share a common ancestor, yet shy away from explaining exactly HOW we evolved from this elusive ancestor. They then go on and say they know its true because DNA analysis and morphological comparisons demonstrate it. Well that's all fine and dandy but tell us HOW it happened. This where Darwinists fail to understand the scope of some of their grandiose claims. I believe it is for that reason that many ardent atheists, such as Fred Hoyle, did not embrace Darwinism; because under scrutiny the proposed mechanism (natural selection acting on random variations caused by genetic mutations) was not enough to account for all the intricate complexities intrinsic to life. As far as human evolution is concerned, I have yet to be shown a sufficient mechanism whereby an apelike creature can turn into something like a human. Did ape-like creatures gradually mutate into humans over millions of years, or were there other forces at work? As far as I've seen, mutations do not supply the kind of raw material necessary to transform an ape-like creature into a human. Can someone explain? Edited by AdminPhat, : fixed paragraph
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New Cat's Eye Inactive Member |
As far as I've seen, mutations do not supply the kind of raw material necessary to transform an ape-like creature into a human. What "kind of raw material" that is necessary are you referring too?
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
As far as human evolution is concerned, I have yet to be shown a sufficient mechanism whereby an apelike creature can turn into something like a human I think you'll find that the mechanism is shaving...
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Chiroptera Inactive Member |
Hello, jbuchanan, and welcome to EvC.
quote: Actually, "they" know that common descent is true because of all the evidence that supports it. Evidence, by the way, that must exist if evolution were true and, if the evidence were different, would show that evolution was false. And evidence that cannot be explained without evolution. One example of evidence, as you point out, comes from morphological comparisons. By carefully comparing the different species, we know that they can be categorized within a nested hierarchical scheme. It is obvious that if the theory of common descent were true, we should be able to see such a nested hierarchical scheme; in fact, if we didn't see such a pattern, that would be a serious blow against the theory of evolution. On the other hand, there is no reason to presuppose that a creator would simply created species according to such a pattern. Now the reason that we think that humans and chimpanzees share a common ancestor is that they sit near each other on the "tree of life". If the tree of life indicates phylogenic relationship (and why else would there be a "tree of life"?) then this indicates that humans and chimpanzees share a recent common ancestor. -
quote: That's fine. But the evidence suggests very strongly that humans did, in fact, evolve from a common ancestor. That much is certain. We may even call it a fact. What could the mechanism be? Well, the only current theory is that it occurred through natural selection acting on randomly occurring variations. This is because we have actually observed natural selection act in some cases, and so it is a known mechanism. Furthermore, we do not know of anything that would prevent natural selection to produce humans from an apelike creature. And all other mechanisms that have been proposed have been shown to be false. So where does the inheritable variation on which natural selection acts come from? That, too, is a good question. So far, from what we know about heredity, is that the nuclear chromosomes in our cells are the material through which physical traits occur. Furthermore, we know that the duplication of genetic material that occurs to produce offspring is not perfect; differences occur, differences which cause variations in physical features. So it is logical to deduce that these genetic mutations are the cause of variations in inheritable features. - So it is possible that the evolution of humans from earlier ape ancestors (which undoubtably did occur, according to the evidence) proceeded through a different mechanism. We currently have someone on another thread trying to resurrect the old idea of orthogenesis, for example. However, the currently accepted model of natural selection on variations in features produced by chromosomes seems to work, and we don't have any other potentially workable models. Edited by Chiroptera, : Added clause to penultimate sentence in second paragraph. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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zcoder Member (Idle past 6208 days) Posts: 66 Joined: |
quote: That answer still danced around with theory to glue it together.
quote: I make bold the word suggests which is used to suggests but stillnot a fact. quote: Here theory was use I think a recap of the meaning of theory is in odyer.In common usage, people often use the word theory to signify a conjecture, an opinion, or a speculation. In this usage, a theory is not necessarily based on facts; in other words, it is not required to be consistent with true descriptions of reality. quote: But also never see it in real life eather, nore the opposite? The author of this was treading on ice, glued with theory and uncertain(suggests) areas. Zcoder....
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Chiroptera Inactive Member |
I'm sorry that you didn't like the wording of my post, Z. Let me rephrase it.
The available evidence makes it quite clear, with no doubts, that the known species have evolved from a common ancestor, and, in particular, that humans and chimps share a recent ancestor. Genetic mutations are known to create new genes, some of which are useful to the organism, and natural selection is known to favor individuals with certain sets of alleles over others. It is quite reasonable, therefore, to assume that natural selection acting on genetically caused variations is the driving force behind common descent. It is possible, though, that the macroevolution that is observed to have occurred over the last three and half billion years is caused by a different mechanism. However, seeing how no other mechanism has withstood scientific scrutiny, and seeing how no one has cogently explained why natural selection is insufficient to have caused macroevolution, it is reasonable to assume that natural selection is the cause. Now, common descent is a fact; natural selection is a reasonable candidate for the mechanism, although admittedly there may be other factors at work. But someone has to either identify those other factors and/or explain why natural selection is not sufficient in itself. -
quote: Actually, the ground beneath my feet is quite solid and steady. Maybe when you sober up you'll find out how steady the footing really is. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi, I am someone who is both inquisitive and skeptical of Darwinian descent with modification. This topic is specifically about the genetic information about a common ancestor to both humans and chimpanzees. To discuss this topic you need to read the referenced article and comment on what it says, not bring in other topics. Your whole post is a much more general question that is beyond the scope of this thread - you should start a new topic for it or find an existing one that discusses general evolution questions. I'll look forward to discussing your issues when you do that. Thanks. compare Fiocruz Genome and fight Muscular Dystrophy with Team EvC! (click) we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Replying to the part that is at least vaguely on topic:
quote: I make bold the word suggests which is used to suggests but still not a fact. The genetic information is discussed in the article linked and referenced on Message 1. If you care to discuss that then point out the problems with the article. Thanks. compare Fiocruz Genome and fight Muscular Dystrophy with Team EvC! (click) we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
anyone interested in the PLOS article referred to in the OP it is at
Genomic Relationships and Speciation Times of Human, Chimpanzee, and Gorilla Inferred from a Coalescent Hidden Markov Model This discusses the genetic evidence for common ancestors with humans, chimps, gorillas and macaques. Enjoy. compare Fiocruz Genome and fight Muscular Dystrophy with Team EvC! (click) we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist ... to learn ... to think ... to live ... to laugh ... to share.
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DorfMan Member (Idle past 6081 days) Posts: 282 From: New York Joined: |
quote:This explains my need to scratch in unusual places at inopportune times. I'm upset with evolution. So much progress and so little progress....where it would be seemly.
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whaler777 Junior Member (Idle past 4343 days) Posts: 12 Joined: |
Obviously words like possibly,perhaps and if seem to be used as concrete evidence. I have had in numerous times teachers of Public schools and Highschools stating to their students that evolution has no evidence to support what they say and that it is only a theory. Why is this being done in the school systems if evolution exists to be true? Also why don't other theory exists. This evolution sounds like the book "War Of The World" (one big hoax). I also would like to see more people that are taking their time and energy to explore other theories so we can stay away from indoctrination. And as far as the Chimp theory goes, what force was in place to decide so many chimps would become human and are there angry chimps out there because they weren't selected? If this force was evident then why doesn't it do it again?
Edited by whaler777, : No reason given. Edited by whaler777, : No reason given.
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