Black People : Misconceptions Around Mitochondrial Eve

Discussion in 'Black People Open Forum' started by RAPTOR, Dec 31, 2010.

  1. RAPTOR

    RAPTOR Well-Known Member MEMBER

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    A Critique of Carl Wieland's AiG article on Mitochondrial Eve

    by Alec MacAndrew



    This is a response to an article written by Carl Wieland and published on the Answers in Genesis website about the concept of 'Mitochondrial Eve' published here:

    http://www.answersingenesis.org/docs/4055.asp (1)

    The AiG article attempts to claim that the mitochondrial evidence is that the Most Recent Common Ancestor of extant humans in the matriarchal line is 6,500 years old. The AiG article begins with a reasonable definition of an MRCA (see link for definition) but then grasps at two relatively recent papers assessing mutational rates in the mitochondrial DNA and rushes to a prematurely triumphant conclusion about them.


    The Underlying Science

    Most of the DNA in the cell of non-bacterial organisms lies in the nucleus. But in eukaryotes there are structures in the cell outside the nucleus called the mitochondria. The mitochondria have several functions, the most obvious of which is that they are responsible for converting 'food' into energy within the cell. The mitochondria also have their own DNA. (There is strong evidence that the complex cells of eukaryotes, which are organisms that have cells with a nucleus, arose originally as a result of parasitism or symbiosis of one simpler organism with another which developed into what's called an obligate relationship - that is one in which the different organisms were so closely bound that they became unable to live without one another and thence became one organism. But, that's a different story). (2), (3), (4)

    DNA material in the nucleus, in the 46 chromosomes in humans for example, comes almost equally from the father and mother - 23 chromosomes from each. (I say almost, because the Y chromosome in mammals is much smaller than the X chromosome). But the mitochondrial DNA comes only from the mother. This means that the mitochondrial DNA follows the female line exclusively. If a woman has no daughters, her mitochondrial DNA (called mtDNA) line dies out.

    Nuclear DNA (the 23 pairs of chromosomes in the nucleus) goes through a process called recombination whereby the chromosomes that are passed on to offspring, say through the mother, are a mixture of the genes in the mother's parent's lineage. However the mtDNA is not a mixture like this, but comes exclusively from the mother. This makes mtDNA a good way to study lineages and to estimate dates of divergence of different groups. The way this is done is to study differences between the mtDNA sequences in different individuals. The nature of the differences provides clues about the relationship between individuals, and the magnitude of the difference indicates how long ago the lineages of the two individuals in the maternal line diverged. There are complications with this process, but that is the basic principle (5)

    This is the way that the age of what has been called mitochodrial Eve is calculated. I don't like the term mitochondrial Eve, because it implies things that it is not - it is simply misleading. So what is it? It is properly termed the most recent common (matrilineal) ancestor (MRCA).

    That means the most recent individual that lived that stands in the direct line through mothers with the entire set of individuals in question. If we are looking at the entire population of people today, the MRCA of that set is called mitochondrial Eve. The matrilineal MRCA of humans is estimated to have lived between 150,000 to 200,000 years ago (note that there are other MRCAs; eg the MRCA as measured by the X-chromosome - since the X-chromosome descends through fathers and mothers, the lineage is different - but there is still the concept of the individual from whom the X-chromosomes of all people alive today descended. That concept is not the same as matrilineal MRCA or Mitochondrial Eve).

    Anyway, the estimate of 150,000 to 200,000 years for matrilineal MRCA was called into question not by one challenge (as Carl Wieland suggests) but by two challenges. However, Carl Wieland's implication that it is now considered to be likely that the matrilineal MRCA lived 6,500 years ago is very misleading.

    There are many other creationist sites which use this research to claim a young (~6,500 year) age for the origin of humans, and many do so with less care than Wieland. Many go so far as to say that these papers make it settled question that biblical Eve existed and that she lived 6500 years ago. Here are a few:

    An article by Charles Creager
    Institute for Creation Research
    The Apologetics Press
    Creation Research Society
    Creation Digest

    (Read more)

    http://www.evolutionpages.com/Mitochondrial Eve.htm
     
  2. Omowale Jabali

    Omowale Jabali The Cosmic Journeyman PREMIUM MEMBER

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    These creationists conflict with their own scholarship which would mean that "Eve" existed before the "creation" of the world which typically is dated as 4004 B.C.

    http://www.lhup.edu/~dsimanek/ussher.htm
     
  3. largo

    largo Well-Known Member MEMBER

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    Just wanted to point out for those who may not be aware, mothers pass their mtDNA to their sons as well. In rare instances mtDNA can be passed on through the father. As males have both an x and a y chromosome.
     
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