Is evolution a fact?
Disclaimer: I was raised a young earth creationist. In college I learned enough science to convince me otherwise. I am now an old earth creationist preferring progressive creation. I am not opposed to the creator using the process of evolution to perform creative acts. I am simply unconvinced by the evidence I've studied. Informal debates have gotten me no new information, so I am hoping a knowledgeable opponent will appear to teach me new things and perhaps persuade me.
The topic is "Is evolution a fact?"
However, according to pro's first round comment's, the resolution we are debating actually seems to be " Is evolution the most likely explanation for the development of biological organism".
That being said, the BoP is shared, in that I must show evolution to be the most likely explanation and con must show a more likely explanation. That being said, let's go.
A prerequsite to debating the validity of evolution is knowing what one means by "evolution". Well in the most general since it can be used to mean change over time but in the spirit of intellectual debate let's use the technical definition, which is as follows:Evolution is http://evolution.berkeley.edu... This is all that is meant by evolution and when one puts it like that, the answer is obviously yes, evolution is true.
-Universal Genetic Code:
Every cell on Earth, from our white blood cells, to simple bacteria, to cells in the petals of flowers, are capable of reading any piece of DNA from any life form on Earth. This is quite convincing evidence for a common ancestor from which all life descended.
Birds-The evolution of birds from dinosaurs was first proposed in the late 1860s by Thomas Henry Huxley, who was a famous supporter of Darwin and his ideas. Evidence from fossils for the reptile-bird link came in 1861 with the discovery of the first nearly complete skeleton ofArchaeopteryx lithographicain Upper Jurassic limestones about 150 million years old near Solenhofen, Germany. The skeleton of Archaeopteryx is clearly dinosaurian. It has a long bony tail, three claws on each wing, and a mouth full of teeth. However, this animal had one thing never before seen in a reptile - it had feathers, including feathers on the long bony tail. Huxley based his hypothesis of the relationship of birds to dinosaurs on his detailed study of the skeleton ofArchaeopteryx.
A reconstructed Archaeopteryx.) This ancient animal seems to constitute strong evidence of the evolution of birds from dinosaurs.
In 1994,Ambulocetus natans, whose name means "walking whale that swims," was described from middle Eocene rocks of Pakistan. This species provides fossil evidence of the origin of aquatic locomotion in whales.Ambulocetus preserves large forelimbs and hind limbs with large hands and feet, and the toes have hooves as in mesonychians.Ambulocetusis regarded as having webbing between the toes and it could walk on land as well as swim; thus, it lived both in and out of the water.
-Ubiquitous Genetic Similarity:
Human beings share approximately 96% of genes with chimpanzees, about 90% of genes in common with cats, 80% with cows, 75% with mice, and so on. This does not prove that we evolved from chimpanzees or cats, though, only that we shared a common ancestor in the past. And the amount of difference between our genomes corresponds to how long ago our genetic lines diverged.
Bacteria colonies may only build up a resistance to antibiotics via evolution. It is vital to note that in every colony of bacteria, there is a minority of individuals that are naturally resistant to certain antibiotics. This is because of the random nature of mutations.When an antibiotic is applied, the initial innoculation will kill most bacteria, leaving behind only those few cells which happen to have the mutations necessary to resist the antibiotics. In subsequent generations, the resistant bacteria reproduce, forming a new colony where every member is resistant to the antibiotic. This is natural selection in action. The antibiotic is "selecting" for organisms which are resistant, and killing any that are not.
I think the aforementioned pieces of evidences is sufficient to substantiate evolution.
(EVOLUTION DOES NOT SAY ANYTHING ABOUT THE ORIGIN OF LIFE)
Are we still evolving?
Yes, however it is not drastic because we are no longer exposed to drastic climates that would require us to do so.
In 2007, a group of researchers looking for signs of recent evolution discovered 1800 genesthat have only become prevalent in humans in the last 40,000 years, many of which are devoted to fighting infectious diseases like malaria. More than a dozen new genetic variants for fighting malaria are spreading rapidly among Africans. Another study found that natural selection has favored city-dwellers. Living in cities has produced a genetic variant that allows us to be more resistant to diseases like tuberculosis and leprosy.
Shrinking Brains:as they shrink, our brains are being rewired to work faster but take up less room. The best explanation is smaller brains are an evolutionary advantage because they make us less aggressive beings, allowing us to work together and to solve problems, rather than tear each other to shreds.
Remember, evolution is merely the change of inherited traits in populations over generations.
I look forward to con's rebuttal and counter-proposal.
http://en.m.wikipedia.org... (see limitations section)
http://www.trueorigin.org... (work cited bird-mammal in phylogenetic tree and discrepancies in phylogenetics)
Pro, you are keen to point out that the origin of life is related but not part of evolution. Evolution is the study of change in species over time. One must have at least one species to study such, and I had no intention of bringing up the subject.
I would like to correct you on one important point. As con, I'm not required to propose a more like origin. If I am able to provide an equally plausible origin, then I should win the debate, because I will have shown that it is plausible that evolution did not take place, a feat I could accomplish without proposing any alternative origin whatsoever. My stated goal is to show that it is *reasonably* possible that evolution is not the answer to our origins.
It is my fault for not being clear in my opening that I'm looking for evidences for macro-evolution specifically. It is fairly agreed upon, even by young earth creationists who I disagree with, that small changes occur in species over time. We have many examples of this, some of which we have been able to observe and document in our own life time. However, it seems taken for granted that small changes can accumulate to form new fundamentally different organisms. Other common logical errors include the idea that creating a phylogenetic tree is evidence for evolution and that similarities in either morphology or DNA support the theory of evolution.
Now I will provide a point address for each previously stated points.
1) universality of genetic code
the theory of evolution does not predict the university of genetic code. Recently, biological engineers have created viable bacteria with 6 letters of DNA as opposed to 4. Evolution does not limit new forms of DNA such as this from arising.
furthermore, this claim is not unique to evolution. There are many types of computer hardware out there which where designed independently of each other, yet they use the same basic parts such as transistors and capacitors. These were not even necessarily influenced by each other. Unless you can rule out the existence of a designer/creator, then the hypothesis remains plausible. We could use Deism as an example. Now let's say that there is a hypothetical creator. If we as creative humans reuse the same parts, why would not a creator do the same by reusing DNA? This statement is neither a prediction of evolution nor unique to it.
2) fossil record (responding to your example, not the entire fossil record)
You have an example of a bird that was similar to a reptile. You concluded that because you found a bird with characteristics of a reptile that birds came from reptiles. This is a valid assumption if you assume the premise of evolution to be true. I do not accept that premise. The way I see it, you are stating that correlation implies causation. It is interesting to note that these same fossils were considered a link between birds and mammals. If you watch the first movie of Jurassic Park you'll find the main character teaching that, and being corrected. We later reconstructed DNA showing more similarity with reptiles than mammals. However, it was morphology (before DNA) that declared them mammals based on body similarities.
I am familiar with the species and others like it. I've read about it both in talkorigins.com and Berkley. Again you have shown similarity, but not causality. I asked for a positive argument for evolution. This, again, requires a predisposition to believing evolution to be counted as evidence. Going back to the hypothetical creator, there is no reason why such a creature would not be created. According to Berkley, the evolution of the whale is still a mystery. The ancestry hasn't been firmly established, and it is assumed that this is the common ancestor based on morphology. I'm looking for facts, not assumptions.
4) Ubiquitous genetic similarity
This is one of my favorites. You have stated that genetic similarity implies common ancestry. You forgot to mention that the sequencing of ancestry based on DNA is impossible. As a side note, the phylogeny trees built by morphologists and those built by DNA engineers are unreconcilable. In some cases with fossils, we have no DNA thus requiring a morphological placement on the tree. But back to DNA... both when it was first discovered and today, scientists struggle with what are described as discrepancies. That means that given three organisms DNA there is no clear inheritance. This is because the offspring would be required to share exact DNA stands not shared by the ancestor. Several explanations have been given to explain these. Retroviruses is one in which a virus permanently alters the DNA of an organism. If the same retroviruse affected both offspring, then the expected inheritance could result. Although we have evidence that retroviruses exists and ate capable of such a result, we have no evidence that they in fact did so. With thousands of discrepancies, it becomes even harder to believe that these are the sole cause of discrepancies. There are additional explanations which lend plausibility to the hypothesis, but I shouldn't be the one teaching you the theory you are defending. Nonetheless, I believe the large number of discrepancies is evidence against evolution, because the shear magnitude of them. Although we have the same potential causes today, we don't see any evidence of creating new species today due to these causes. Again I empathize, hypothesis gives plausibility, not probability.
I will refrain from addressing your further points about the change in bacteria and in humans. These are examples of micro evolution which have not lead to a fundamental change in either species. In fact, you didn't show that humans today couldn't bed with humans from 40,000 years ago, nor did you show that simply by breeding we wouldn't be able to regain the capability to breed with them again.
I would like to give a further rebuttal to give my kind opposition something to respond to. The theory of evolution predicts small charms over time which sometimes lead to new and complex abilities. Sonar is one outstanding ability in this category as it is shared by bats and dolphins. Granted, bats use ears and dolphins their jaw. In both cases, the organism must be able to produce the sonar, be able to hear the sonar, know when to use the sonar, correctly perform complex mathematics to to interpret the sonar, and finally take appropriate actions in response to it. In this complex system, there is expected to be an order given small changes over time. I see no examples in nature where a creature has a partial capability for a complex system such as this. Why is that?
You pointed out websites that show aquatic mammals descending from land mammals. Land mammals are known to be the only category of species that sleep with both halves of their brain. Aquatic mammals had to reacquire unihemispheric sleep in order to come up to breath while sleeping. This is not the expectation of nested hierarchy. The fact is, nested hierarchy is not predicted by evolution as you seem to assume in your example of shared DNA. It simply accommodates it. If you want to use nested hierarchy as evidence in favor of evolution, you must accept counter examples such as this one as evidence against evolution. But the question is then asked, what does evolution predict? Honestly, it can accommodate anything. The duck billed platypus is considered a mystery, not evidence against evolution. There are many mysteries that scientists believe will be solved with more time and data.
To give a reason to doubt small changes over time, I shall bring up punctuated equilibrium. Upon examination of the fossil record, we find new species arising is fairly uncommon. It only happens over a few million years then takes a break for a few billion. I believe every family of species is seen in the Cambrian explosion. Wikipedia lists about 11 explanations for the explosion and debunks all of them. In 70 years, no one has found an explanation for punctuated equilibrium either. It seems to me that evolution is based on a lot of untested hypothesis'.
Let me propose progressive creationism. It is the belief that with an old earth, an intelligent designer chose to miraculously create new species on earth over a long period of time. I will not pretend to defend such a position which is outside the scope of this debate. I have shown several expectations of evolution shown to be propped up by unproven hypothesis and mathematical inprobability. Progressive creationism suffers neither of these set backs (because it makes less predictions). Again, an intelligent creator is plausible until proven otherwise. Can you put forth evidence to show macro evolution more likely than progressive creationism?
I can't convince con of evolution and no one can, because he wants exclusive claims. This wouldn't be so bad if he didn't assert progressive creationism as an alternative. There is nothing that evolution has, that creationism can't, aside from common decent , however in order to validate that, he says I would already have to assume evolution to be true. It's a trap.
THERE ARE NO STRONG PREDICATIONS OF CREATIONISM.
For anything, the creationist can merely say "god made it that way".
P1) Everything with intelligence, comes from prior intelligence.
P2) Life has intelligence
P3) Life came from intelligence
P4) That intelligence came from god
C1) God came from intelligence(per P1)
C2) If god does not need to come from prior intelligence, then P1 is violable and then life does not need to come from intelligence(which is logical because god would be more intelligent than life.)
With design, one ecounterd an unavoidable infinite regression or a violation of the initial premise.
Universal Genetic Code:
Con advances a false analogy in comparing natural life forms and artificial bacteria, further more he takes this to an ad absurdum in making an comparison to computers. This analogy does not even help him out, just the opposite actually.
"There are many types of computer hardware out there which where designed independently of each other, yet they use the same basic parts such as transistors and capacitors. These were not even necessarily influenced by each other. "
Computers ae composed of the same basic parts, yet computers that are produced in similar time periods have a more similar make up. For example, A macbook pro is closer to a Chromebook pixel, than a Dell Inspiron 800. However, all three have a common predecessor of the GRiD Compass 1101. So con's analogy actual proves my point.
Once again, he tries to fit this into his creationist hypothesis, but this is not convincing because EVERYTHING fits into his creationist hypothesis.
A universal or extremely close to universal genetic code is what one would expect to see, if all life had a common ancestor. I'm not asserting that correlation proves causality, because that would be a Post hoc ergo propter hoc, but I'm saying that the correlation, in this instance, implies causality and I believe I am justified in that that assertion.
Con says nothing to refute my point.
"You concluded that because you found a bird with characteristics of a reptile that birds came from reptiles. This is a valid assumption if you assume the premise of evolution to be true."
I'm not saying this is absolute proof, but it is compelling evidence, further more, you agree that it's evidence. However you say that I must start with the assumotion that evolution is true. In this case, we are going to make it no where fast, because, once again, creationism is so vague and inspecific, that it can pretty much ecnompass everything.
Con says: "I am familiar with the species and others like it. I've read about it both in talkorigins.com and Berkley. Again you have shown similarity, but not causality. I asked for a positive argument for evolution. This, again, requires a predisposition to believing evolution to be counted as evidence. Going back to the hypothetical creator, there is no reason why such a creature would not be created."
Once again he accuses me of a post hoc ergo propter hoc, and once again im not asserting that this is proof of causality, but merely asserting that in this instance there does seem to be a correlation and something caused it. Con's cause is a supernatural god. Mine is natural processes. However, my natural explanation is more plausible. Occam's razor roughly states that the explanation that provokes the least variables and satisfies the question is most likely to be correct. We live in a natural world and in a natural world we expect natural causes.In this instance we have an event that can be explained naturally. since we live in a natural world and any given events most likely has a natural cause, we should accept the natural cause, i'e evolution by natural selection. Con's explanation invokes a supernatural cause, however, if we allow for a supernatural cause in a natural world, how would we distinguish between the two? If they are equally plausible, then by invoking a supernatural explanation, we invoke questions that CAN'T ever be answered. We agree on the facts, we just disagree on the implications.
Ubiquitous genetic similarity and Morphology and stuff:
con seems to just lazily discard morphology as some pseudoscience, all though the physical anthropologist and evolutionary biologist would surely not agree with him. Morphology is evidence of evolution and DNA seems to play a part. It is common knoweledge to all biologist that genetic mutation causes morphological variances.
Genetic mutations have the ability to alter the functionality of a protein, provided it takes place within the section of the gene that codes for the protein. A mutation also has the ability to alter when or where the gene is activated, if it occurs in a gene's control elements.All these genetic mutations can alter morphology. The internal control elements of development assure that an altered body part still integrates effectively with the rest of the organism.
The implication is that the evolution of morphology can occur via the mutation of s single gene. It is not the case that all of the genes must mutate at once.
"I can't convince con of evolution and no one can, because he wants exclusive claims. This wouldn't be so bad if he didn't assert progressive creationism as an alternative. There is nothing that evolution has, that creationism can't, aside from common decent , however in order to validate that, he says I would already have to assume evolution to be true. It's a trap."
I did not assert progressive creation was true. I explicitly stated, "I will not pretend to defend such a position which is outside the scope of this debate." My point was that there are many possible origins of which evolution is only one. I gave the example of progressive creation, because I feel it fits well with the data at hand. Pro did address this issue by stating roughly that we should assume the most likely answer is the most natural answer. Specifically, he stated that because most (or all) event we experience arise from natural causes, we should assume our origin arose from natural causes, thus evolution should be preferred over a super-natural one. I believe we can agree that the generation of completely new species dramatically different in body type from the parents has not been observed and documented by humans outside the fossil record. So we should also agree that such an event is rare. In fact, in the history of the fossil record, it is a very rare occurrence. That statement is backed by punctuated equilibrium.
To the best of my knowledge, we do not have evidence that small mutations can account for macro changes to organisms. We have only observed micro changes. If we have not observed macro evolution, then we do not know that it is a possible cause. It is believed that small changes over time can account for transitions between, but this is an extrapolation, not based on observation. I requested Pro provide counter evidence, which he has failed to do. Observing what are believed to be transitions among organisms is the exception, not the rule. It appears to be uncommon as opposed to common. So Pro suggests that an uncommon event is to be extrapolated out to a very very large number of events simply because it is a naturalistic cause as opposed to a super-natural cause. Pro's argument rests on natural causes taking preference to super-natural causes. This is an assertion which is ideological and based on experiences of a skeptic who has no experience with super natural events which so many around the world claim to encounter. There is no logical reason to believe that naturalism should be accepted over super-naturalism.
"Con says nothing to refute my point [on the fossil record]."
Your statement shows I failed to effectively communicate, because I did indeed address the point under the heading "2) fossil record". Let me state again. The way I understand your argument is that we have found fossils that appear to be from a creature that has characteristics of both reptiles and birds. Your conclusion is that reptiles evolved into this species of creature which later evolved into birds. The fact that there is a transition between reptiles and birds is used as evidence that reptiles were the genetic ancestors of birds. I do not need to repeat my rebuttal that your assumption rests on asserting naturalism is more likely than super-naturalism.
"THERE ARE NO STRONG PREDICATIONS OF CREATIONISM."
There are no strong predictions made of evolution either.
Pro claimed, "A universal or extremely close to universal genetic code is what one would expect to see, if all life had a common ancestor. I'm not asserting that correlation proves causality, because that would be a Post hoc ergo propter hoc, but I'm saying that the correlation, in this instance, implies causality and I believe I am justified in that that assertion."
First I'll point out that he believes his position is justified. I think he believes this, because it provides a plausible naturalistic answer that fits his predisposition to naturalism. That is more evidence of his predisposition than it is that evolution took place.
Second, I will point out that his claim is not correct. The Universal genetic code is NOT a prediction made by the theory of evolution. In my previous rebuttal, I pointed out that humans have engineered a viable bacteria with 6 letters in its DNA (link in previous rebuttal). There is nothing in evolutionary theory that suggests this would not take place. The theory of evolution does not predict a fundamental unity at all. If we postulated a world where there was not a fundamental unity, evolution could still hold. It would need only be adapted to a different set of evidence.
I will revisit an argument Pro forgot to address from my previous rebuttal. Darwinian evolution predicts that genes shared by two descendant organisms would be expected to be shared by their ancestor. This is far from the case. To quote wikipedia: http://en.wikipedia.org...
Molecular systematics is an essentially cladistic approach: it assumes that classification must correspond to phylogenetic descent, and that all valid taxa must be monophyletic.
The recent discovery of extensive horizontal gene transfer among organisms provides a significant complication to molecular systematics, indicating that different genes within the same organism can have different phylogenies.
In addition, molecular phylogenies are sensitive to the assumptions and models that go into making them. They face problems like long-branch attraction, saturation, and taxon sampling problems: This means that strikingly different results can be obtained by applying different models to the same dataset.
I hope you caught the last part about the inability of scientists to agree on a particular phylogenetic tree because they are unable to resolve the quirks found by DNA sequencing. This has been a problem since the beginning, even before we were able to sequence DNA so accurately.
I will quote from http://trueorigin.org...
These conflicts have long been recognized. In 1986, biochemist Christopher Schwabe wrote:
Molecular evolution is about to be accepted as a method superior to paleontology for the discovery of evolutionary relationships. As a molecular evolutionist I should be elated. Instead it seems disconcerting that many exceptions exist to the orderly progression of species as determined by molecular homologies; so many, in fact, that I think the exception, the quirks, may carry the more important message. (Schwabe, 280.)
"Once again, he tries to fit this into his creationist hypothesis, but this is not convincing because EVERYTHING fits into his creationist hypothesis."
I will give a direct quote from http://trueorigin.org...
The ease with which this precise adjustment could occur was illustrated two decades ago, when "[t]he reality of the "mammal-bird," a hypothetical common ancestor of birds and mammals, [was] a contentious issue in modern systematics." (Mike Benton, 18.) Brian Gardiner"s cladistic analysis indicated that birds were most closely related to mammals, which relationship was supported by two Cambridge scientists" analysis of molecular data. That view was readily accepted by some, even to the point that one French paleontologist "published a restoration of the hypothetical common ancestor between birds and mammals"a sort of warm-blooded, hairy/feathery climbing insect eater!" (Mike Benton, 18.) Branches can be rearranged, even between mammals and birds, without skipping a beat in terms of commitment to common ancestry.
It turns out that EVERYTHING fits into a evolutionary hypothesis as well. I pointed out in my previous rebuttal that evolution does not predict nested hierarchy. However, Pro still attempts to use nested hierarchy as evidence for evolution.
There were several points I made that Pro did not even mention in his rebuttal, some of which are a summary of above. I shall form a list here in hopes that they can easily be addressed in his final rebuttal.
1) Nested hierarchy is not 100% found in nature, but it is used by Pro as an evidence for evolution
2) There are known natural causes for the essential structure of DNA to be altered (e.g. 6 letter DNA bacteria) which have been exploited in a lab, but are not observed to occur in nature.
3) The phylogenetic trees between morphology and DNA sequencing are irreconcilable.
4) The phylogenetic trees among DNA sequence analysis technics are irreconcilable due to too many quirks.
5) There are no strong predictions made by the theory of evolution which, if incorrect, could be falsified using the scientific method.
6) Evidence that naturalism is more likely than super natural creation.
I want to re-iterate that the topic is clearly stated "Is evolution a fact?". Pro must assert enough evidence to prove that evolution is a fact beyond the shadow of doubt. Con (myself) must show that there is reasonable doubt. Pro has made the assertion that evolution is fact, thus the burden of proof lies mostly on him. Con (myself) has not asserted any particular origin hypothesis. Con must either show that there is insufficient evidence to support evolution, or given an example of another similarly plausible hypothesis.
As Con, I have cast doubt on the theory of evolution by pointing out that it has been molded to fit the data available, and could be remolded if we lived in a very different world, or if new data becomes available that contradicts it. I assert that it is in the scope of possibility that there is a divine creator who designed organisms similar to how we design machines.
Pro has not shown evidence that the theory of evolution could be proven false by evidence if it is the case that it is false.
I thank Pro for taking this debate with me, and I look forward to hearing a response to my 6 arguments.
"If I am able to provide an equally plausible origin, then I should win the debate,"
These are con's own words, I hope it is clear that he has not provided an equally plausible origin.
He has not defended progressive creationism at all, even though that is what he would need to do in order to substantiate creationism as an equally plausible origin. He has merely asserted creationism. " I assert that it is in the scope of possibility that there is a divine creator who designed organisms similar to how we design machines."
Yes it's possible, but you have given us zero reasons to think this is the case.
"Evolution predicts that living things will be related to one another in what scientists refer to as nested hierarchies—rather like nested boxes. Groups of related organisms share suites of similar characteristics and the number of shared traits increases with relatedness. This is indeed what we observe in the living world and in the fossil record and these relationships can be illustrated as shown below."
Snakes and Lizards similarities:
-Jacobsen sensory organs, used to catch prey.
-two copulatory organs in male (hemipenes).
-flexible skulls and elastic jaws
- High DNA synonymity
-96% DNA Synonymity("The number of genetic differences between humans and chimps is ten times smaller than that between mice and rats.")
-Complex greeting and communication
Organisms closer together on the hierarchy share more similar traits and organisms farther apart have more similar traits, yet we still see similar traits in all organisms.
"But at a more inclusive level of life’s hierarchy, we share a smaller set of inherited traits in common with all primates. More inclusive still, we share traits in common with other mammals, other vertebrates, other animals. At the most inclusive level, we sit alongside sponges, petunias, diatoms and bacteria in a very large “box” entitled: living organisms."
Con says: "2) There are known natural causes for the essential structure of DNA to be altered (e.g. 6 letter DNA bacteria) which have been exploited in a lab, but are not observed to occur in nature.'
Natural causes in the sense that they are not supernatural, but they are not naturally occuring. If we recall, con says the following in regards to his claim: "Recently, biological engineers have created viable bacteria with 6 letters of DNA as opposed to 4."
Artificially produced organisms are bound to differ from naturally arisen organisms, to compare the two in such a manner is a false analogy, as you will recall me demonstrating in my prior round.
Reconciling Phylogenic Trees:
I'll address this even though con fails to provide a thorough analysis and example of when this is the case. Also no one has claimed evolution is perfect or complete.
"An algorithm to find gene duplications in phylogenetic trees in order to improve gene function inferences has been developed in a collaboration between the the Helix team from INRIA Rhône-Alpes and the ‘biométrie moléculaire, évolution et structure des génomes’ team from the UMR ‘biométrie, biologie évolutive de Lyon’. The algorithm and its software is applicable to realistic data, especially n-ary species tree and unrooted phylogenetic tree. The algorithm also takes branch lengths into account."
Given apt algorithms, it is now the case, that it becomes a possiblity and plausability to accurately deduce a species ancestry via analysis of genes sequences. Genes, of course, are vulnerable to mutations during the evolution process(i/e genetic mutation), and therefor the corresponding (homologous) sequences in various species differ from each other. A tree may be constrcuted via the data of sequences comparison, relating genes and species history: i.e a phylogenetic tree. Occasionally a phylogenetic tree has results contrary to the species tree (constructed via amalysis of physiological and paleontological data ). These disagreements may be resolved via a gene being duplicated in a genome, and each resulting copy possesing a respective history. Subsequently, a node in a phylogenetic tree can be the division of an ancestral species into two others, as well as a gene duplication. More specifically, in a family of homologous genes, paralogous genes must be distinguished from orthologous genes. "Two genes are orthologous if the divergence from their last common ancestor results from a speciation event, while they are paralogous if the divergence results from a duplication event."
("It is essential to make the distinction because two paralogous genes are less likely to have preserved the same function than two orthologues. Therefore, if one wants to predict gene function by homology between different species, it is necessary to check whether genes are orthologous or paralogous to increase the accuracy of the prediction.")
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