Liffrea
01-20-2010, 09:32 AM
I've lifted this from another forum, it was posted by a member, sorry there are no links so I don't know how valid this is:
Evolutionary biologists often date the divergence of species by the differences in genetic sequences in mitochondrial DNA. Even if paternal DNA is inherited very rarely, it could invalidate many of their findings. (NewScientist.com, "Mitochondria can be inherited from both parents", August 23, 2002)
For this reason, the "mitochondrial Eve" thesis put forward on The Discovery Channel is one totally invalidated by the above finding.
Things change rapidly in science. What is popular one day, is not the next. Theories come, and theories go. And so it is with mitochondrial Eve. She once was in vogue as "the woman of the moment," so to speak. Now, she has become virtually the "crazy aunt in the attic" that no one wants to admit even exists.
But it was not forbidden fruit that caused her demise this time around. The "passing" of one of evolution's most familiar icons is due to new scientific facts that have surfaced since her introduction in 1987. If humans received mitochondrial DNA only from their mothers, then researchers could "map" a family tree using that information. And, if the mutations affecting mtDNA had indeed occurred at constant rates, then the mtDNA could serve as a molecular clock for timing evolutionary events and reconstructing the evolutionary history of extant species. It is the "ifs" in these two sentences that are the problem.
Mitochondrial Eve is alleged to have lived in Africa at the beginning of the Upper Pleistocene period (between 100,000 and 200,000 years ago). She has been described as the most-recent common ancestor of all humans on Earth today, with respect to matrilineal descent. The validity of these assertions, however, is dependent upon two critically important assumptions: (1) that mtDNA is, in fact, derived exclusively from the mother; and (2) that the mutation rates associated with mtDNA have remained constant over time. However, we now know that both of these assumptions are wrong!
First, let us examine the assumption that mtDNA is derived solely from the mother. In response to a paper that appeared in Science in 1999, anthropologist Henry Harpending of the University of Utah lamented: "There is a cottage industry of making gene trees in anthropology and then interpreting them. This paper will invalidate most of that" (as quoted in Strauss, 1999, 286:2436). Just as women thought they were getting their fair shake in science, the tables turned. As one study noted:
Women have struggled to gain equality in society, but biologists have long thought that females wield absolute power in a sphere far from the public eye: in the mitochondria, cellular organelles whose DNA is thought to pass intact from mother to child with no paternal influence. On page 2524 however, a study by Philip Awadalla of the University of Edinburgh and Adam Eyre-Walker and John Maynard Smith of the University of Sussex in Brighton, U.K. finds signs of mixing between maternal and paternal mitochondrial DNA (mtDNA) in humans and chimpanzees. Because biologists have used mtDNA as a tool to trace human ancestry and relationships, the finding has implications for everything from the identification of bodies to the existence of a "mitochondrial Eve" 200,000 years ago (Strauss, 286:2436, emp. added).
One year later, researchers made this startling admission:
Mitochondrial DNA (mtDNA) is generally assumed to be inherited exclusively from the mother…. Several recent papers, however, have suggested that elements of mtDNA may sometimes be inherited from the father. This hypothesis is based on evidence that mtDNA may undergo recombination. If this does occur, maternal mtDNA in the egg must cross over with homologous sequences in a different DNA molecule; paternal mtDNA seems the most likely candidate…. If mtDNA can recombine, irrespective of the mechanism, there are important implications for mtDNA evolution and for phylogenetic studies that use mtDNA (Morris and Mightowlers, 2000, 355:1290, emp. added).
In 2002, a study was conducted that concluded:
Nevertheless, even a single validated example of paternal mtDNA transmission suggests that the interpretation of inheritance patterns in other kindreds thought to have mitochondrial disease should not be based on the dogmatic assumption of absolute maternal inheritance of mtDNA…. The unusual case described by Schwartz and Vissing is more than a mere curiosity (Williams, 2002, 347:611, emp. added).
And now we know that these are more than small "fractional" amounts of mtDNA coming from fathers. The August 2002 issue of the New England Journal of Medicine contained the results of one study, which concluded:
Mammalian mitochondrial DNA (mtDNA) is thought to be strictly maternally inherited…. Very small amounts of paternally inherited mtDNA have been detected by the polymerase chain reaction (PCR) in mice after several generations of interspecific backcrosses…. We report the case of a 28-year-old man with mitochondrial myopathy due to a novel 2-bp mtDNA deletion…. We determined that the mtDNA harboring the mutation was paternal in origin and accounted for 90 percent of the patient's muscle mtDNA (Schwartz and Vissing, 2002, 347:576, emp. added).
Ninety percent! And all this time, evolutionists have been selectively shaping our family tree using what was alleged to be only maternal mtDNA!
As scientists have begun to comprehend the fact, and significance, of the "death" of mitochondrial Eve, many have found themselves searching for alternatives that can help them maintain their current beliefs regarding human origins. But this recombination ability in mtDNA makes the entire discussion a moot point. As Strauss noted:
Such recombination could be a blow for researchers who have used mtDNA to trace human evolutionary history and migrations. They have assumed that the mtDNA descends only through the mother, so they could draw a single evolutionary tree of maternal descent—all the way back to an African "mitochondrial Eve," for example. But "with recombination there is no single tree," notes Harpending. Instead, different parts of the molecule have different histories.
Thus, "there's not one woman to whom we can trace our mitochondria," says Eyre-Walker (1999, 286:2436, emp. added).
Evolutionary biologists often date the divergence of species by the differences in genetic sequences in mitochondrial DNA. Even if paternal DNA is inherited very rarely, it could invalidate many of their findings. (NewScientist.com, "Mitochondria can be inherited from both parents", August 23, 2002)
For this reason, the "mitochondrial Eve" thesis put forward on The Discovery Channel is one totally invalidated by the above finding.
Things change rapidly in science. What is popular one day, is not the next. Theories come, and theories go. And so it is with mitochondrial Eve. She once was in vogue as "the woman of the moment," so to speak. Now, she has become virtually the "crazy aunt in the attic" that no one wants to admit even exists.
But it was not forbidden fruit that caused her demise this time around. The "passing" of one of evolution's most familiar icons is due to new scientific facts that have surfaced since her introduction in 1987. If humans received mitochondrial DNA only from their mothers, then researchers could "map" a family tree using that information. And, if the mutations affecting mtDNA had indeed occurred at constant rates, then the mtDNA could serve as a molecular clock for timing evolutionary events and reconstructing the evolutionary history of extant species. It is the "ifs" in these two sentences that are the problem.
Mitochondrial Eve is alleged to have lived in Africa at the beginning of the Upper Pleistocene period (between 100,000 and 200,000 years ago). She has been described as the most-recent common ancestor of all humans on Earth today, with respect to matrilineal descent. The validity of these assertions, however, is dependent upon two critically important assumptions: (1) that mtDNA is, in fact, derived exclusively from the mother; and (2) that the mutation rates associated with mtDNA have remained constant over time. However, we now know that both of these assumptions are wrong!
First, let us examine the assumption that mtDNA is derived solely from the mother. In response to a paper that appeared in Science in 1999, anthropologist Henry Harpending of the University of Utah lamented: "There is a cottage industry of making gene trees in anthropology and then interpreting them. This paper will invalidate most of that" (as quoted in Strauss, 1999, 286:2436). Just as women thought they were getting their fair shake in science, the tables turned. As one study noted:
Women have struggled to gain equality in society, but biologists have long thought that females wield absolute power in a sphere far from the public eye: in the mitochondria, cellular organelles whose DNA is thought to pass intact from mother to child with no paternal influence. On page 2524 however, a study by Philip Awadalla of the University of Edinburgh and Adam Eyre-Walker and John Maynard Smith of the University of Sussex in Brighton, U.K. finds signs of mixing between maternal and paternal mitochondrial DNA (mtDNA) in humans and chimpanzees. Because biologists have used mtDNA as a tool to trace human ancestry and relationships, the finding has implications for everything from the identification of bodies to the existence of a "mitochondrial Eve" 200,000 years ago (Strauss, 286:2436, emp. added).
One year later, researchers made this startling admission:
Mitochondrial DNA (mtDNA) is generally assumed to be inherited exclusively from the mother…. Several recent papers, however, have suggested that elements of mtDNA may sometimes be inherited from the father. This hypothesis is based on evidence that mtDNA may undergo recombination. If this does occur, maternal mtDNA in the egg must cross over with homologous sequences in a different DNA molecule; paternal mtDNA seems the most likely candidate…. If mtDNA can recombine, irrespective of the mechanism, there are important implications for mtDNA evolution and for phylogenetic studies that use mtDNA (Morris and Mightowlers, 2000, 355:1290, emp. added).
In 2002, a study was conducted that concluded:
Nevertheless, even a single validated example of paternal mtDNA transmission suggests that the interpretation of inheritance patterns in other kindreds thought to have mitochondrial disease should not be based on the dogmatic assumption of absolute maternal inheritance of mtDNA…. The unusual case described by Schwartz and Vissing is more than a mere curiosity (Williams, 2002, 347:611, emp. added).
And now we know that these are more than small "fractional" amounts of mtDNA coming from fathers. The August 2002 issue of the New England Journal of Medicine contained the results of one study, which concluded:
Mammalian mitochondrial DNA (mtDNA) is thought to be strictly maternally inherited…. Very small amounts of paternally inherited mtDNA have been detected by the polymerase chain reaction (PCR) in mice after several generations of interspecific backcrosses…. We report the case of a 28-year-old man with mitochondrial myopathy due to a novel 2-bp mtDNA deletion…. We determined that the mtDNA harboring the mutation was paternal in origin and accounted for 90 percent of the patient's muscle mtDNA (Schwartz and Vissing, 2002, 347:576, emp. added).
Ninety percent! And all this time, evolutionists have been selectively shaping our family tree using what was alleged to be only maternal mtDNA!
As scientists have begun to comprehend the fact, and significance, of the "death" of mitochondrial Eve, many have found themselves searching for alternatives that can help them maintain their current beliefs regarding human origins. But this recombination ability in mtDNA makes the entire discussion a moot point. As Strauss noted:
Such recombination could be a blow for researchers who have used mtDNA to trace human evolutionary history and migrations. They have assumed that the mtDNA descends only through the mother, so they could draw a single evolutionary tree of maternal descent—all the way back to an African "mitochondrial Eve," for example. But "with recombination there is no single tree," notes Harpending. Instead, different parts of the molecule have different histories.
Thus, "there's not one woman to whom we can trace our mitochondria," says Eyre-Walker (1999, 286:2436, emp. added).