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What if Adam is an aberration?

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  • #46
    The actual Mt Eve is a theoretical person as is the actual Y-Chrom Adam. Our Most recent relative is much younger than these people are. Also, we each have different founders. The problem is that there are no records on who these parents were.

    Tishkoff, S., et al. (1996) Global patterns of linkage disequilibrium at the CD4 locus and modern human origins. Science 271, 1380-1387.

    The most recent common patrilineal ancestor of any two males, and the most recent common matrilineal ancestor of any two individuals can be determined by genealogical DNA tests. The tests use mitochondrial DNA for matrilineal inheritance or Y-chromosome-DNA for patrilineal inheritance.
    When a species invades a new area, the original, small population is called a founder population.
    An effective founder population consists only of those whose genetic print is identifiable in subsequent populations. Because in sexual reproduction, genetic recombination ensures that with each generation only half the genetic material of a parent is represented in the offspring, some genetic lines may die out entirely, even though there are numerous progeny.
    The founder effect was defined by Ernst Mayr in 1963 to be the effect of establishing a new population by a small number of individuals, carrying only a small fraction of the original population's genetic variation. As a result, the new population may be distinctively different, both genetically and phenotypically, from the parent population from which it is derived.
    http://en.wikipedia.org/wiki/Founder_effect

    Mitochondrial Eve is the most recent common matrilineal (female-lineage) ancestor for mtDNA, not the most recent common ancestor (MRCA) of all humans. The MRCA's offspring have led to all living humans, but Mitochondrial Eve must be traced only through female lineages, so she is estimated to have lived much longer ago than the MRCA. While Mitochondrial Eve is thought to have been living around 150,000 years ago, the MRCA is estimated to have been living only 10,000 plus years ago.
    Y-chromosomal Adam is not the same individual at all points in human history; the Y-mrca of all humans alive today is different from the one for humans alive at some point in the remote past or future: as male lines die out, a more recent individual becomes the new Y-mrca.
    Human mitochondrial DNA (inherited only from one's mother) and Y chromosome DNA (from one's father) show coalescence at around 70,000 years ago. In other words, all living humans' female line ancestry and male line ancestry trace back to a small number of people alive at that time. However, such coalescence is genetically expected and does not indicate a population bottleneck, because most human ancestors are neither female line nor male line ancestors (for example, one's mother's father's ... mother's father). A population bottleneck would only be indicated if DNA coalesced more recently than genetically expected.
    Coalescence describes the idea that any sample of genetic sequences from any number of living things (that is, bacteria, archaea and eukaryotes) can be traced back to a common ancestor in the past. Due to random elimination of ancient genetic lineages, with constant population size of the taxons considered, the most recent common ancestor (MRCA) remains at a constant time distance from the present.
    There are actually three popular theories today (Aug 2002)

    There are three main theories for the evolution of modern humans: the multiregional
    model, the recent African origin (RAO) model and the assimilation model (all reviewed
    in REF. 112).
    The multiregional model proposes that there was no single geographical origin for
    modern humans but that, after the radiation of HOMO ERECTUS from Africa into Europe
    and Asia ~800,000–1.8 million years before present (yr BP), there were independent
    transitions in regional populations from H. erectus to Homo sapiens.This model is
    supported primarily by the continuity of certain morphological traits in the fossil
    record (for example, the robust cheekbones observed in H. erectus fossils from Southeast
    Asia and in modern Australian aborigines),which indicate that modern populations
    evolved over very long periods of time in the regions where they are found today.
    Simultaneous evolution from H. erectus to H. sapiens in dispersed populations could
    have been achieved through extensive gene flow between populations, requiring a large
    EFFECTIVE POPULATION SIZE to sustain gene flow among geographically diverse populations.
    The RAO model proposes that all non-African populations descend from a H. sapiens
    ancestor that evolved in Africa 100,000–200,000 yr BP. This ancestor then spread
    throughout the world, replacing archaic Homo populations (for example, the
    Neanderthals). This model is supported by the fossil record, as the earliest modern
    human fossils were found in Africa and the Middle East, dating to 90,000–120,000 yr BP
    (REFS 60,112). The RAO model predicts that all genetic lineages derive from a recent
    common African ancestor and that non-African populations should carry a subset of the
    genetic variation present in modern African populations.
    The assimilation (or hybridization) model proposes that gene flow between the early
    human populations was not equal over time and space.This model allows for some gene
    flow between modern humans that migrated from Africa and archaic populations (for
    example, the Neanderthals) outside Africa. So, the evolution of modern humans could
    have been due to a blending of modern characters derived from African populations
    with local characteristics in archaic Eurasian populations.This model predicts that the
    modern gene pool derives from variable contributions of genes from archaic African
    and non-African populations.
    GENETIC ANALYSIS OF AFRICAN
    POPULATIONS: HUMAN EVOLUTION
    AND COMPLEX DISEASE
    http://www.uvm.edu/~rsingle/stat395/...enetics-02.pdf
    Sarah A. Tishkoff * and Scott M.Williams‡§
    Africa is one of the most ethnically and genetically diverse regions of the world. It is thought to be
    the ancestral homeland of all modern humans, and is the homeland of millions of people of the
    recent African diaspora. Because of the central role of African populations in human history,
    characterizing their patterns of genetic diversity and linkage disequilibrium is crucial for
    reconstructing human evolution and for understanding the genetic basis of complex diseases
    Last edited by GregKiroKH; 8 November 2006, 08:50 PM.

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    • #47
      Originally posted by GregKiroKH
      The actual Mt Eve is a theoretical person as is the actual Y-Chrom Adam.
      Nope, each was in fact a real person. They are not theoretical constructs, but actual living people.

      Our Most recent relative is much younger than these people are. Also, we each have different founders.
      That is not strictly true. There is a single MRCA for each locus in the human genome. Different locii can have different MRCAs, each of which was a real person and each of which might be younger or older than Y-Adam or mtDNA-Eve.

      There are actually three popular theories today (Aug 2002)
      Perhaps, but only the RAO is supported by DNA evidence. The other two theories are not compatible with the DNA evidence.

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      • #48
        Me: The actual Mt Eve is a theoretical person as is the actual Y-Chrom Adam. Our Most recent relative is much younger than these people are. Also, we each have different founders. The problem is that there are no records on who these parents were.
        That is just what I think after I read some articles. I just do not know who these people are. (This is really true with laboratory subjects . . . )

        Originally posted by vineviz
        Nope, each was in fact a real person. They are not theoretical constructs, but actual living people.
        I think I understand your point, that is why I included "Coalescence describes the idea that any sample of genetic sequences from any number of living things (that is, bacteria, archaea and eukaryotes) can be traced back to a common ancestor in the past." The only problem is that I do not know who this person is, so that person is a theoretical person even if he/she is a real person.

        Originally posted by vineviz
        That is not strictly true. There is a single MRCA for each locus in the human genome. Different locii can have different MRCAs, each of which was a real person and each of which might be younger or older than Y-Adam or mtDNA-Eve.
        What example are you refering too? Each allele has a unique MRCA, yes. Two alleles make a locus. But what about the human individual who were the parents of . . . ? (I guess you read Ernst Mayr's biography?)

        Originally posted by vineviz

        Perhaps, but only the RAO is supported by DNA evidence. The other two theories are not compatible with the DNA evidence.
        I generally like the RAO and common ancestor theory, but I have to be fair to everyone.

        What about different Founders Effects for each SNP and STR? I think I am finding one group around 200 B.C. to 400 A.D. with my Y- haplotype.
        Last edited by GregKiroKH2; 9 November 2006, 12:27 PM.

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        • #49
          Genomic science versus Genesis

          Forcing genomic science to fit the account of Genesis appears now to be "a case not to be undertaken".
          The Bible recounts the conventional wisdom of contemporary science of about 1400 BC when the two Creation versions of Genesis were apparently written from verbal traditions, collated reputedly by Moses. Some of these precede that writer of Genesis far back in time. For example, they contain some Urrian Gilgamesh material (originally believed ca.4000 to 8000 BC) , including the Flood story.
          As evidence for verbal continuity, I was impressed by the description in the Gilgamesh story centered on "Great Walled Uruk" (Jericho or Baghdad ?), of how "stone men" were being used to move boats across what sounds like the Bosporus. This was recorded later by explorers like Alexander the Great, and is again confirmed by modern investigation. Constant currents and countercurrents exist there at different depths, and by lowering nets full of stones , a boat has a choice of direction of drift.
          However, the (reasonable in 1400 BC) Genesis postulate of an Adam and an Eve now becomes unlikely in terms of mDNA and Y DNA timescales, which separate such a "couple " by multimilllenia. It is also not compatible with what we know of humanoid evolution from the fossil record indicating graduality. It is likely that there never was a point in time when a pair of cro-magnon type individuals, autosomally just like ourselves, existed complete for the first time as our first ancestors.
          Was there not instead a sliding scale defining each autosomal characteristic we identify as defining our species, such as brain size, speech and language ability, degree of upright bipedalism as a percentage of daily use, use of tools etc. The list is very long, and for each individual, reached any given degree of "completion" in a partial rather than a comprehensive state. There must have been large numbers of offspring in which the The Y and mt identifiers would often represent parents who were not equally "human" in the autosomal sense. Some think that is still the case today, perhaps explaining the divorce rate?

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