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. Theory’s 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. Theory’s 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. Theory’s 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. Theory’s 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 <1% 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 17:303-313. [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. 41:683-688.] • Science and Nature: Genes. The Truth About Adam and Evehttp://www.bbc.co.uk/science/genes/dna_detectives/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/2001/01/010111194453.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/