Monday, February 25, 2013

A Second, Closer Look at DNA – Part II – The Problems With DNA “Science"

Continuing from the last post, it was not forbidden fruit in the Garden of Eden that caused mitochondrial Eve’s 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 “if"s in these two sentences that are the problem.
Researchers say that Eve was sturdy and fruitful and problem lived in a small group that scoured the plains for food, though they cannot decide whether it was Asia or Africa
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 B. Eyring 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 Evelyn Strauss, “MtDNA Shows Signs of Paternal Influence,” Science, Vol 286, p2436, 1999).  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."  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.  As Strauss stated: “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.”
Geneticists claim that DNA can be a valuable tool when doing genealogical research on a family and that tests can indicate clan relationships and connect a family tree back to a distant ancestor
One year later, however, 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. Morris and Mightowlers added, “If MtDNA can recombine, irrespective of the mechanism, there are important implications for MtDNA evolution and for phylogenetic studies that use MtDNA.”
In 2002, a new study was conducted by Schwartz and Vissings 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.”  Williams added that this case study “Is more than a mere curiosity.”
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 the Swartz and Vissing 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. 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. And Harpending added, “with recombination there is no single tree.” In addition, Eyre-Walked says.“ Instead, it has been found that different parts of the molecule have different histories, and as Eyre-Walker concluded, “there’s not one woman to whom we can trace our mitochondria.”
In fact, we couldn’t agree more.
Secondly, the assumption that the mutations affecting 
mtDNA did indeed occur at constant rates, and that researchers who made the initial announcement about Eve not only gave a location for this amazing female, but also proposed the time period during which she was supposed to have lived.  However, in order for the mtDNA theory to be of any practical use, those scientists had to assume that random mutations in the DNA occurred at documented, steady rates.  As stated in the last post, if the speculation was one mutation every 1,000 years, and they found a difference of 10 mutations between us and our ancient hypothetical ancestor, they then could infer that that ancestor lived 10,000 years ago. Scientists who used this concept to determine the age of mitochondrial Eve referred to this proposed mutation rate as a “molecular clock.” One group of researchers, headed by Rodriguez-Trelles, described the process as follows:
“The hypothesis of the molecular clock of evolution emerged from early observations that the number of amino acid replacements in a given protein appeared to change linearly with time.  Indeed, if proteins (and genes) evolve at constant rates they could serve as molecular clocks for timing evolutionary events and reconstructing the evolutionary history of extant species.” And, of course, it sounded good in theory, but the actual facts tell an entirely different story.  As these same researchers went on to admit:
“The neutrality theory predicts that the rate of neutral molecular evolution is constant over time, and thus that there is a molecular clock for timing evolutionary events.  It has been observed that the variance of the rate of evolution is generally larger than expected according to the neutrality theory, which has raised the question of how reliable the molecular clock is or, indeed, whether there is a molecular clock at all. The observations are inconsistent with the predictions made by various subsidiary hypotheses proposed to account for the overdispersion of the molecular clock.”
(See the next post, “A Second, Closer Look at DNA – Part III – The Problems With DNA “Science” Part II, The Demise of Mitochondrial Eve,” and further information on the problems with previously thought female-only MtDNA)

1 comment:

  1. What's wrong with saying: Here is what we have found so far, as opposed to: this is how it is? Why do the people whom we trust to inform us feel a need to teach us WHAT to think instead of HOW to think?