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.

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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 Evehttp//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/