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Ali NasserEddine

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Posts posted by Ali NasserEddine


  1. 22 hours ago, CharonY said:

    Actually there are potential scenarios in which hierarchies could exist, though I am not sure whether examples exist. One case would be the isolation of a small subpopulation which would undergo rapid speciation (say, due to strong selection). At the same time, the original population maintains a stable gene pool (e.g. because of size, free gene flow etc.). After divergence, the original population could still be indistinguishable from the ancestor population, whereas the isolated one would become new species or sub-species (depending on divergence in the given time frame).

     

    Dear Charon, your comment is highly appreciated. For someone who is completely out of the domain like me, any information can cause distortion. So, thanks alot.

    On the other hand, could you please advise on the door of this science for someone new to the field? Do you think that the starting point would be a bachelor in specific biology field? Or is there a shortcut? (for example, particular set of courses). The hope is to contribute to this field, and arrive at a method. From my experience in scientific research (holder of PhD), there would be a huge space for relatively easy improvements in any field.


  2. Hi Moontanman, thanks a lot. All are well noted.

    7 minutes ago, Moontanman said:

    No, think of your first cousin, you both share a common ancestor who might still be alive but neither of you are that ancestor nor ancestral to each other. Object X can be your ancestor and still be alive. It reminds me of the old question if humans descended from monkeys why are there still monkeys. The answer is that while humans and extant monkeys share a common ancestor and that ancestor, if alive today would be classified as a monkey, we are not descended from any monkeys alive today... 

    This is understood, but what I am exactly after is to know whether there is a methodology that allows us to identify the hierarchical relation between two living objects. I used the example of wolves and dogs because it is common, but it could be anything else, like two types of birds. Actually, the educated guess of @StringJunky is exactly to the point. If his idea is correct, then, my requirement would be satisfied.

    However, after all the help I got through this forum, and for which I am sincerely grateful, I think that proving such relations is not straight forward. My initial thought was that it can be done through DNA tests, but it seems I was wrong.


  3. 3 hours ago, CharonY said:

    I am not sure about the natural history of how folks first determined it. But rather obviously it was known that dogs are a domesticated species and that it would have to originated from some wild forms and the most likely candidate (geographically and morpohologically) were wolves or perhaps coyotes. As genetic analyses have shown that grey wolves and dogs are most closely related, the conclusion seems rather obvious. 

    However, if we want to be very precise, it is actually quite a bit more complicated. It is not clear, for example if the ancestor of the dog is actually the gey wolf we see today, or perhaps a common ancestor of the modern grey wolf. Also, there is potential admixture afterward. I am not sure how well that has been resolved, though.

    Thanks a lot Charon for the clarification; well noted and very much appreciated.

    3 hours ago, Bender said:

    Not only can DNA analysis track species through time, it can also show migration patterns. Link

    Thanks a lot Bender for the link. However, if they could trace a story that dates back to 33,000 years ago, wouldn't it be easily possible to identify the ancestry relation between wolves and dogs that are currently available. I refer to the last post by @CharonY:

    4 hours ago, CharonY said:

    were wolves or perhaps coyotes

    So, it is uncertain. Please note that Charon was nominated by many here as one of the most familiar with this science field in this forum.

    I really wish not to lose the point that brought me here. If you could help me understand the following, I would be indeed grateful:

    8 hours ago, Ali NasserEddine said:

    To understand it correctly, if we consider a sample of 10 wolves and 10 dogs, we would find DNA evidence of wolves in all the 10 dogs, but not vice versa. However, as per @Moontanman comment, it is possible to find evidence of dogs in some wolves (3 out of 10 for example). If my understanding is correct, could you please advise if there is any scientific reference for this?

     


  4. 4 minutes ago, CharonY said:

    Maybe this can help you in looking at these things.

    Thanks a lot Charon, well noted. I looked at the link; very illustrative dendrograms.

    However, I am confused. I understand that dogs and wolves are the same species, but how could we tell that wolves are the ancestors? This concept has been long in existence, even before the advancement in modern science and scientific tools.

    Have scientists derived this conclusion based on physical similarities? I was hoping that the case that @StringJunky presented is true because this would be a shortcut for what I am looking for. I quote it here:

    On 2/14/2018 at 6:24 PM, StringJunky said:

    To OP: If we take a population of dogs and analyse their DNA and then do the same with wolves, I think you would find DNA evidence of wolves in all dogs but not the other way around; not all wolves carried the mutation which led to dogs, so we can surmise, with a high degree of confidence, that dogs came after wolves.

    If the concept of subspecies is based on similarities, well, it might be but it also might not be. For example, as per the suggestion of @DrP, I watched this video on the laryngeal nerve. At 0.37, he says: "obviously a ridiculous detour, no engineer would ever make a mistake like that". Here is another viewpoint on the matter "RLN Is Not Evidence of Poor Design".

    Just so I don't get lost, could you please share your opinion on the question I asked before in response to @StringJunky reply that I quoted above?

    3 hours ago, Ali NasserEddine said:

    To understand it correctly, if we consider a sample of 10 wolves and 10 dogs, we would find DNA evidence of wolves in all the 10 dogs, but not vice versa. However, as per @Moontanman comment, it is possible to find evidence of dogs in some wolves (3 out of 10 for example). If my understanding is correct, could you please advise if there is any scientific reference for this?


  5. Hi Charon, many thanks for this information; well noted. Further to your reply, could you please help me understand some of your statements?

    1 hour ago, CharonY said:

    Dogs are a subspecies of wolves. For all intents on purposes, they are the same species. However, we do know the timeline when dogs arose (as they are domesticated). 

    Were we able to identify this relation (subspecies) only because they were domesticated?

    1 hour ago, CharonY said:

    I.e. existing (extant) species are not derived from each other and therefore are not the ancestor of each other.

    Doesn't this contradict the concept that wolves are the ancestors of dogs? Unless you mean that there was a living object x, which became a wolf at one point, and the wolf became a dog at a later stage.

    1 hour ago, CharonY said:

    There is also the concept of molecular clocks where we can use the divergence as a means to estimate when the respective species split (though that is even trickier).

    This is very important to my understanding. Was the molecular clock used for identifying the relation between wolves and dogs?


  6. 21 hours ago, koti said:

    Theres an anti spam thing which gives new members only 5 posts to post untill some time passes. As to your question of whether x comes from y with 100% certainty the answer is yes and no depending on the system. If we are trying to detemine childs mother, we can know with 100% certainty when we witness the birth. DNA tests never give 100% certainty.

    Many thanks Koti. Now, I am able to post again.

    Well noted regarding the certainty.

    21 hours ago, Area54 said:

    Science tends not to deal with 100% certainties. I see Moontanman has already mentioned that.

    I understand your phrase "x is the source of y" to be the same as "x is the ancestor of y". (That would be the more usual way of putting it and so if you see that phrase you know it is referencing the topic you are interested in.)

    We can establish these sorts of relationships with a good probability of success, but no single technique is used to establish these relationships. Rather comparison of genotype (the DNA of living specimens, or geologically recent specimens), anatomy, embryology, geographic distribution, behvioural traits, etc. are all in the mix. Keep in mind also that we are building on and steadily improving two or more centuries worth of obsevation, collection and analysis.

    I appreciate that this is not the clear cut answer you are looking for, but the net result of these approaches is that we can say - with 100% certainty - that amphibians evolved from fish, that reptiles evolved from amphibians, that mammals evolved from the synapsid reptiles and so on. As we get more detailed we are more likely to be in the position of saying that x was the ancestor of y, or closely related to the ancestor of y.

    I hope that clarifies rather than confuses.

    As koti said we have no doubt at all that dogs evolved from wolves, for here we have the luxury of being able to examine the DNA of both. In a similar way we know that some humans, primarily Europeans have a few % of Neandertal DNA, indicating cross breeding between the two species in Europe. This conclusion is possible because some Neandertal fossils contain enoough residual DNA for analysis.

    Thanks a lot; much appreciated. I see the point. This means that if I want to conduct tests to confirm such relations, I need to fully understand all the surrounding concepts. I hoped for a shortcut, i.e. single test (concept) such as DNA that makes the results available. I will invest as much time as needed as soon as possible.

    21 hours ago, StringJunky said:

    To OP: If we take a population of dogs and analyse their DNA and then do the same with wolves, I think you would find DNA evidence of wolves in all dogs but not the other way around; not all wolves carried the mutation which led to dogs, so we can surmise, with a high degree of confidence, that dogs came after wolves.

    Hi SJ, many thanks for your contribution. When I first read this particular reply, I thought I was done. But then, I read @Moontanman comment on this. To understand it correctly, if we consider a sample of 10 wolves and 10 dogs, we would find DNA evidence of wolves in all the 10 dogs, but not vice versa. However, as per @Moontanman comment, it is possible to find evidence of dogs in some wolves (3 out of 10 for example). If my understanding is correct, could you please advise if there is any scientific reference for this?

    19 hours ago, Area54 said:

    There is a 2004 study in Italy into the origin of black wolves. Occurrence of black wolves in the Northern Apennines, Italy . (https://link.springer.com/article/10.1007/BF03192528) Unfortunately the article itself is behind a paywall, but here is the abstract:

    The occurrence of black-coated individuals in wolfCanis lupus Linnaeus, 1758 populations is not surprising itself, but their presence in populations recovering from a severe numerical decline has been considered a possible sign of crossbreeding with the domestic dog. In the northern Apennines (Italy), black wolves occur at a non-negligible frequency. In a 3300 km2 area, 22% of wolves observed and 23% of all dead wolves found were represented by animals with a completely black coat. One ‘black’ wolf belonging to the studied population was analysed by a set of microsatellite loci, and no trace of hybridization was found in its ancestry. This result induced us to consider the occurrence of a black phenotype in this area possibly derived from a natural combination of wolf alleles in coat colour determining genes, and not necessarily as the result of crossbreeding with the domestic form.

    And this may be the study that Moontanman was aware of through the documentary. "Molecular and Evolutionary History of Melanism in North American Gray Wolves" And the good news is that the complete article is freely available. In the meantime here is the abstract.

    Morphological diversity within closely related species is an essential aspect of evolution and adaptation. Mutations in the Melanocortin 1 receptor (Mc1r) gene contribute to pigmentary diversity in natural populations of fish, birds, and many mammals. However, melanism in the gray wolf, Canis lupus, is caused by a different melanocortin pathway component, the K locus, that encodes a beta-defensin protein that acts as an alternative ligand for Mc1r. We show that the melanistic K locus mutation in North American wolves derives from past hybridization with domestic dogs, has risen to high frequency in forested habitats, and exhibits a molecular signature of positive selection. The same mutation also causes melanism in the coyote, Canis latrans, and in Italian gray wolves, and hence our results demonstrate how traits selected in domesticated species can influence the morphological diversity of their wild relatives.

    Note that the conclusion here  (black wolves arose from interbreeding with dogs) contrasts with the conclusion in Italy (the black colouration arose independently).

    Hi A54, very interesting. Really good on you what you have learnt by yourself in this scientific field. The only problem for me is that for fully understanding these papers, I need to be comfortable with the scientific terms. Unfortunately, in my case, this is only possible if I thoroughly study the basics of this field. On the other hand, could you please advise on the answer I asked SJ for?


  7. 4 hours ago, Area54 said:

    @Ali NasserEddine I belive that your question is fundamentally "How does cladistics operate?" My biology is largely self taught and so has large gaps and probably lots of misunderstandings, but I think a look at cladistics would help you. Cladistics is an effective approach at biological classification that explicitly deals with the sort of relationships you are asking about. Try these links and come back with any questions that arise from them.

    https://en.wikipedia.org/wiki/Cladistics

    http://palaeos.com/systematics/cladistics/cladogram.html

    https://rationalwiki.org/wiki/Cladistics

    Thanks a lot Area54; very helpful.

    Actually, this is about what I am looking for. However, it doesn't answer my question. For example, in the first link, we can read "therefore, members of a group are assumed to share a common history and are considered to be closely related."

    What I want to know is not whether science can determine whether two living objects are closely related, but if x, with 100% certainty, is the source of y.

    Could you please advise if I am getting something wrong?

    -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

    Hi @Moontanman

    For some reason, I can't reply to posts anymore; so, I put my reply here.

    Thanks a lot for the information. If we consider dogs and wolves, I always hear that the latter is the origin of the former. Do you think science can confirm that dogs were wolves since they both still exist? Please note that I am not asking whether science can show that they are related or very related.


  8. 4 hours ago, DrP said:

    There are clues in anatomy that show that we are all related to fish (look up the Laryngeal nerve in Fish and Giraffes - there is a good youtube vid of a giraffe dissection). These days though the DNA shows that we are related...  it is pretty obvious which one came from who. ;-) IDK how DNA analysis shows this hereditary, but I think it can be used to deduce who are related and which came from what. You need to wait for an expert or look it up on the net if you want deeper details.   

    Thanks a lot. I just watched the video (Richard Dawkins demonstrates laryngeal nerve of the giraffe).

    Stunning. Really stunning, and extremely good to know. Thanks again; much appreciated.

     

    2 hours ago, Moontanman said:

    Are you asking if there is a modern animal that is ancestral to mammals? 

    No. What I am after is to know whether current scientific tools can, with absolute certainty, tell that x came from y (ex: dogs came from wolves). If yes, I am keen to fully know and learn this technique.


  9. 2 minutes ago, DrP said:

    There are evolutionary charts which depict the relationships and ancestry of all the animals.... we all descend from fish.  I think these have been backed up with more scientific data from DNA analysis of animals and fossil remains since the 1990's.  So - a DNA test will show your relationship between wolves and dogs.

    I hope this helps - there are those that are far more knowledgeable than I here in this field that can help you further should you require it.

    Thanks a lot DrP; much appreciated. I understand that science can relate two mammals, but I need to know if it can allow us to deduce, with great certainty, who originated who.

    For example, in a DNA paternity testing, "only the characteristics inherited by the child from the father are determined" (source at the end). This makes me feel that if  two samples are collected (child & father), unless I know which one belongs to the father, I can't identify it. Thus, the test only determines if there is a relation, but not who originated who.

    Again, thanks a lot. I appreciate your help, and will be waiting for others' input as per your post.

    Source:

    https://www.bj-diagnostik.de/paternity-test/paternity-test-father-child

     

    1 minute ago, koti said:

    Evolution works more like a tree with various branches growing from each other, some dry out and fall off, some connect and form other branches, its a large and complex system. It doesn’t work in a simple manner like pop science tells us. You might find this helpful:

    https://en.m.wikipedia.org/wiki/Evolution_of_mammals

    Thanks a lot Koti for your reply. Regarding the link, this is exactly why I am asking here. Unfortunately, I haven't been exposed to biology since at least 18 years ago. I hoped that by posting here, someone would direct me to the exact concept (tool) which can be used for such identification, if any; so I can study it. Kindly note that if this concept doesn't exist, I am considering to enroll for bachelor in biology in the near future.

    Thanks again.

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