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The Search for Genetic Eve and Adam

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5-7 Million Years Ago (MYA) Divergence from the Chimpanzee Lineage ... Human DNA has 6,000,000,000 nucleotides. 400,000 times as much DNA exists which could ... – PowerPoint PPT presentation

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Title: The Search for Genetic Eve and Adam


1
The Search for Genetic Eve and Adam
2
Divergence Points
  • 5-7 Million Years Ago (MYA) Divergence from the
    Chimpanzee Lineage
  • 4.4 MYA Ardipithecus Ramidus first know
    Hominid
  • It is not known if this was part of human descent
    chain or even actually bipedal.
  • 3.9 4.2 MYA Australopithecus Anamensis
    Definitely bipedal

3
From Anamensis to Sapiens
  • Australopithecus Anamensis
  • Australopithecus Afarensis
  • Homo Habilus
  • Homo Erectus 1.81 1.61 MYA
  • Homo Sapiens
  • Transition Species 400,000 years ago
  • Homo Sapiens Sapiens 200,000 years ago
  • Homo Sapiens Neanderthalensis 200,000 years ago
  • Evidence seems to indicate that H. Sapiens
    Sapiens and H. Sapiens Neanderthalensis are not
    as far apart as once thought. They may be
    sub-branchs of the same tree that recombined.

4
Theorys of Human Evolution
  • Multi-regional Model
  • H. Sapiens Sapiens transitioned from H. Erectus
    across a wide portion of Africa and Eurasia.
  • Fossil evidence shows that either H. Sapiens
    spread very fast after transition or transitioned
    in multiple areas. This is supported by H.
    Sapiens Sapiens and H. Sapiens Neanderthalensis.
  • Genetic exchange across the area would have
    occurred to accomplish this.

5
Theorys of Human Evolution
  • Problems with Multiregional Model
  • Would require persistent and extensive migration
    patterns to disperse the necessary genes.
  • H. Erectus existed in China and Java for at least
    100,000 years after emergence of H. Sapiens
    Sapiens indicating a slow migration from the
    transition point.

6
Theorys of Human Evolution
  • Out of Africa Theory
  • Noted from the fact that African populations have
    more differences between themselves than the rest
    of the human genotypes.
  • It is thought that transition was actually from a
    small number of individuals.

7
Theorys of Human Evolution
  • Back to Africa Theory
  • Early H. Sapieans transitional forms evolved in
    central to west Eurasia, then migrated to Africa
    and hybridized with H. Erectus and other
    hominids.
  • The fact that Eurasians are more closely related
    to each other than to Africans supports this.
  • This transition would still have been from an
    originally relatively small number of individuals.

8
Searching for Eve
  • Mitochondrial DNA Technique
  • mtDNA exists outside the cell nucleus
  • mtDNA is exclusively inherited along the maternal
    line

9
mtDNA Study
  • A.C. Wilson and R.L. Cann, 'The Recent African
    Genesis of Humans,' Scientific American, April
    1992, pp. 68-73
  • Used 100 ethnically diverse individuals.
  • The common mtDNA ancestral sequence was coalesced
    to a Eve about 200,000 years ago.

10
Searching for Adam
  • The Y chromosome is exclusively passed thru the
    Paternal lineage
  • The ZFY gene on the Chromosome was picked for a
    study.

11
ZFY Study
  • R. L. Dorit, H. Akashi, and W. Gilbert, 'Absence
    of Polymorphism at the ZFY Locus on the Human Y
    Chromosome,' Science, vol. 268, pp. 1183-1185,
    1995
  • Compared 38 men of diverse geographical origins.
  • Their common ZFY ancestral sequence was coalesced
    to a Adam about 270,000 years ago.

12
Problems with Studies
  • mtDNA is 16,000 nucleotides in size.
  • Human DNA has 6,000,000,000 nucleotides
  • 400,000 times as much DNA exists which could and
    would have been inherited from other individuals
    than Eve.
  • mitochondria genes do not normally recombine.
  • They seem to follow the mathematical rules more
    associated with bacterial genetics than human
    genetics.
  • Seemingly small increases in efficiency lt1 can
    quickly and easily become the predominate
    characteristic in the population.

13
Problems with Studies
  • In the search for Adam, the search did not
    include enough of the chromosome
  • The ZFY gene is only a portion of the overall
    chromosome, total coalesced could be very
    different.
  • Both studies shown had too few starting
    candidates
  • Eve and Adam coalesced at very different time
    spans.
  • Adam coalesced well into the transition period
    between H. Erectus and H. Sapiens

14
Genealogy
  • Gene Genealogy
  • A gradually coalesced towards a unique DNA
    sequence (the root of the tree)
  • Individual Genealogy
  • An increase by a factor of two each generation of
    ancestors which contributed to the genetic
    make-up of the individual.

15
Human Diversity
  • It has been estimated from analysis of the HLA
    immune genetic complex that human populations
    have never sunk down below a 50 or 100 thousand
    population Ayala Escalnte, et al1995, p205.
  • The Genetic make-up of Humans would have come
    from many individuals over the course of many
    generations, not a single Eve or Adam.

16
Conclusion
  • There is not any single individual at this time
    that could be identified as the Mother or Father
    of the Human race.
  • We have many genetic Mothers and Fathers however
    the their genes have all been jumbled up through
    generations of sexual reproduction.
  • It is possible future techniques may allow the
    discovery of a genetic Adam but it is very
    likely that this Adam might not be what we
    consider Human.
  • It is doubtful that any individual Eve could
    ever be identified because of the gene scrambling
    seen thru sexual reproduction.

17
References
  • C Ayala, F.J. 1995. Adam, Eve, and Other
    Ancestors A Story of Human Origins Told by
    Genes. HPLS 17303-313. similar to Ayala, F.J.
    1995. Genes and Origins The Story of Modern
    Humans. Book review of The History and Geography
    of Human Genes by L.L. Cavalli-Sforza, P.
    Menozzi, and A. Piazzo. J. Mol. Evol.
    41683-688.
  • Science and Nature Genes. The Truth About Adam
    and Eve http//www.bbc.co.uk/science/genes/dna_det
    ectives/adam_and_eve/index.shtml
  • Ayala, F.J. The myth of eve molecular biology
    and human origins. Science 270,1930-1936 (1995).
  • King MC Motulsky AG 2002 Mapping human history.
    Science 298 2342-2342.
  • Evolution - May 1999 Re Mitochondrial Eve
    Discussion Thread at American Scientific
    Affiliation (ASA)
  • ScienceDaily New Fossil Study Rejects "Eve
    Theory" And Supports Diverse Ancestry Of Modern
    Humans www.sciencedaily.com/releases/2001/01/01011
    1194453.htm
  • New fossil study rejects Eve theory and
    supports diverse ancestry of modern humans Diane
    Swanbrow, The University Record, January 22, 200,
    http//www.umich.edu/urecord/
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