"Out of Africa" theory: a done deal

Discussion in 'Human Science' started by Fraggle Rocker, Feb 22, 2008.

  1. Roman Banned Banned

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    Nice ad hom. Have anything to back up your inbreeding theory? Just some feelings? I remain unconvinced.
     
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  3. iceaura Valued Senior Member

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    The genetic diversity isn't crucial to my main point, but I think that dogs have been found to be more diverse and of older origin than that - at least, that is what I keep running into.

    My original info seems to be all pay-per-view ("Nature" magazine and the like), but the following is typical fo what I recall from more technical papers:

    http://www.workingdogweb.com/DogOrigins.htm
     
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  5. John99 Banned Banned

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    Roman, how is that an ad hom? i was being honest.
     
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  7. Fraggle Rocker Staff Member

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    Dude, the source material for that article is ten years old. It is totally obsolete. The definitive DNA study was completed about four years ago. A summary of the research was published in Smithsonian magazine, and the National Geographic devoted their entire building here in Washington to a more extensive popularization of the research about a year later. All dogs are descended from a single population in central China, and that population still has the genetic markers.

    They've traced the evolution of the various breeds, determined which ones were developed first and which later, and tracked the migratory paths their ancestors took to found newer breeds. Some of the discoveries were amazing. The Pekinese is one of the oldest breeds, as old as the ultra-utilitarian mastiff. Apparently people began breeding dogs for pure companionship much earlier than we had assumed.

    As for the article's assertion that primitive people were assumed not to have the skill to domesticate an animal... This has been superseded by the hypothesis that dogs domesticated themselves. There are two possible ways, and they may both have occurred. One is that dogs and humans kept running into each other's hunting parties and each was impressed with the other's advantages. Dogs can track their prey by smell and they can run faster, whereas humans are more cunning and have pointy sticks that can kill a frelling mammoth. They might have converged on the same quarry at the same time and discovered that by working together they were able to bring down more game, so eventually the cooperation became deliberate rather than accidental.

    The other hypothesis is that since dogs are scavengers as well as hunters, they thought the perfectly good food we leave lying on the ground in our camps was dog heaven, and we didn't mind their janitorial services. They appreciated our warm fires and we appreciated their nocturnal vision to protect the camp. Not to mention their outrageous loyalty, risking their lives to run off bears and lions. The young of both species naturally played together and since both species are pack-social with a sense of hierarchy it was easy for the larger, smarter species to be acknowledged as leader, so long as the arrangement meant better hunting and more meat for everybody.

    This theory (either or both hypotheses) is borne out by our later experience with cats. Cats joined us around 5000BCE, at the dawn of historical times, and we know a little more about the details. The economy of scale that characterizes civilization resulted in huge stores of grain. Rodents soon descended on our granaries, stealing quite a bit of our food and fouling it with their feces. Cats came in out of the forest to hunt the rodents. As soon as humans realized what was going on they started putting treats out for the cats and leaving doors open so they could come inside during bad weather. Again, the relationship was formed cooperatively out of mutual benefit. Nobody "domesticated" anybody.
     
  8. iceaura Valued Senior Member

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    It was the only one I could find that wasn't subscription. But you are correct in my reliance on studies more than four years old.

    I vaguely recall the study you mention, but I don't recall it narrowing the present genetic diversity that much (aside from ascribing some large morphological differences to expression-rate changes in a few core genes) - more of an establishment of the original ur-dog, and so forth. Free access link ?

    Tangent to the thread, of course - free to ignore.
     
  9. Fraggle Rocker Staff Member

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    I recall the report admonishing us that we obviously didn't know as much as we thought we did about the correlation between morphological differences and genetic diversity! They stated that the difference between the DNA of any two dogs you could find--a Great Dane and a Chihuahua, or a bull terrier and a poodle--is less than that between a human from Norway and one from New Guinea.
     
  10. Hercules Rockefeller Beatings will continue until morale improves. Moderator

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    A few points:

    1) Most mitochondrial inheritance is maternal, but not all. A mammalian zygote receives some paternal mitochondria (a few percent of the total). This has been known for a while now, but the idea that all mt inheritance is maternal persists for some unknown reason.

    2) There is no difference between male (sperm) and female (ovum) mitochondria (that I am aware of), so the exclusion of paternal mt from the fertilized ovum is unlikely to be based on any structural or genetic difference.

    2) The mitochondria in mammalian sperm are concentrated in the “neck” whereas the nucleus and enzymes required for ovum penetration are in the “head”. It could well be that it is this segregation of the mt and the nuclear DNA in the sperm that results in most of the paternal mt being excluded from the ovum during fertilization. This is my speculation; I don’t definitely know the answer.
     
  11. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Thanks for the speculation and facts. Perhaps the sperm, like some lizards, when they are about to be eaten, drops its tail upon entry to the egg? - I think that is about what you are suggesting, but perhaps not so specifically.
     
  12. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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    Hercules:

    Do you have any citations for your assertion that some of the mt-DNA inheritance can be from the sperm? The article cited by BillyT which I had also cited [and initially provided by Zarlok] clearly stated that while a few of the sperm mitochondria make it into the ovum, they are 'hunted down and killed' so that none remain, and ALL inheritance is purely maternal.
     
  13. Pandaemoni Valued Senior Member

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    Paternal inheritance of mtDNA is rare and still, to my knowledge, the subject of some speculation as to how it occurs, but there are cases of it that have been "on the scientific radar" for several years now.

    http://content.nejm.org/cgi/content/full/347/8/576

    http://www.nature.com/hdy/journal/v93/n4/full/6800516a.html
     
  14. Walter L. Wagner Cosmic Truth Seeker Valued Senior Member

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    Pandaemoni:

    Thanks, excellent cites. This appears to be a very recent field of study, and I suspect more will be done in the coming years. While this does not appear to effect the general dating technique of mt-DNA, it does means that it is possible that some very few females might actually obtain some of their mt-DNA from their fathers rather than exclusively from their mothers. Whether this would include development into ovarian tissue [one study showed it was dominant in the muscle tissue] would be the next avenue of research, to see if it can be subsequently inherited via the maternal lineage. How this skews the mt-Eve results I'm not certain.
     
    Last edited: Feb 29, 2008
  15. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    My thanks too.

    I note that the firstr link is case study of man with extreme "exercise intolerance" (only can run a few feet and then feels like it was marthon - pain from toxin build up in mussels, I think.) Although, as I unnderstand it, only a very small fraction of the cell's DNA comes from the mitochondria, the ability to make ATP, which is how the cells get energy, how the mussels can do work etc. does come only from the mitochondria DNA. His is mainly from his father and has defect which gave it a great reproductive advantage. (It could very quickly be reproduced as it left long string of coding out whendoing so. - Dam those "selfish genes"!) Thus even though greatly outnumbered in the fertalized egg, it is now the dominate mitochondria in this man's mussels.

    Who ever said: "Women are the weaker sex." really had it all screwed up! First, in the normal course of developement, the egg 's female mitochondria (the m-Eve mitochondria) has a battle with the paternal mitochondria and kills them all off. If, as in this rare case, the paternal can win this battle (by "cheating" - i.e. leaving long sections out to more quickly make more copies) then the result is a very weak man.

    Better keep this under our hat guys - the women libers may hear and have scientific proof they are the stonger sex.

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    Last edited by a moderator: Feb 29, 2008

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