Mythos 8 – Genetic Adam and Eve

 

Geneticists have provided some confusing information about humanity in the past couple decades, perhaps none more confusing than the research into mitochondria and Y chromosomes. Without a DNA sample, it is not currently possible to reconstruct the complete genetic makeup of any individual who died very long ago. By analyzing descendants’ DNA however, parts of ancestral genomes are estimated by scientists. Mitochondrial DNA and Y-chromosome DNA are commonly used to trace ancestry in this manner. Mitochondrial DNA is generally passed unmixed from mothers to children of both genders, along the maternal line, or matrilineally.(1)C. William Birky (2008) “Uniparental inheritance of organelle genes” Current Biology, Volume 18, Number 16, Pages R692–R695 The inherited DNA in the male case is his nuclear Y chromosome rather than the Mitochondrial DNA.

newsweek

The Cover of the Magazine Newsweek Breaking the Mitochondrial Eve and Y-Chromosomal Adam

The idea that a “Mitochondrial Eve”, a woman from whom all people inherit their mitochondrial DNA, must have existed was obvious once mitochondrial DNA was discovered. Likewise the idea of a Y-chromosomal Adam followed, each named after the Judeo-Christian matriarch and patriarch. The initial researchers did not use the term “Mitochondrial Eve” or even the name “Eve” in their original paper; it appears to be a catchy term popularized by the media.(2)N. A. Johnson (2007) Darwinian Detectives: Revealing the Natural History of Genes and Genomes, Page 92 The name appeared in a 1987 article in Science by Roger Lewin, headlined “The Unmasking of Mitochondrial Eve.”(3)R. Lewin (1987) “The unmasking of mitochondrial Eve” Science, Volume 238, Number 4823, Pages 24–26 The biblical connotation was very clear from the start. The accompanying research news in Nature had the obvious title “Out of the garden of Eden”(4)J. Wainscoat (1987) “Out of the garden of Eden” Nature, Volume 325, Number 6099, Page 13

The scientific work of determining the time and place of the last woman from whom we all inherit our Mitochondrial DNA was carried out by Allan Wilson, of the University of California, Berkeley, with his doctoral students Mark Stoneking and Rebecca L. Cann, but was initially theoretical. The study was advanced by doctoral student Rebecca L. Cann, who started collecting Mitochondrial DNA in 1979, and cataloging them based on ethnicity. She collected samples from US hospitals from American women of diverse ethnic backgrounds, including Asians, South Pacific Islanders, Europeans, and Africans. Their initial observation of the mitochondrial DNA of 100 individuals led them to resolve that it was possible to trace back individual female lineages hundreds of generations thereby reaching the point of a common ancestor.(5)Rebecca L. Cann et al. (1982) “Evolution of human mitochondrial DNA: a preliminary report” Progress in Clinical Biological Research, Volume 103, Part A, Pages 157–165

Inheritance of Mitochondrial DNA and Y-Chromosomal DNA

Inheritance of Mitochondrial DNA and Y-Chromosomal DNA

Mitochondrial Eve is estimated to have lived between 99,000 and 234,000 years ago,(6)Pedro Soares et al (2009) “Correcting for Purifying Selection: An Improved Human Mitochondrial Molecular Clock and its Supplemental Data” The American Journal of Human Genetics, Volume 84, Issue 6, Pages 740–759 while Y-chromosomal Adam is estimated to have lived 163,900 to 260,200 years ago.(7)Eran Elhaik et al. (2014) “The ‘extremely ancient’ chromosome that isn’t: a forensic bioinformatic investigation of Albert Perry’s X-degenerate portion of the Y chromosome” European Journal of Human Genetics, Volume 22, Number 9, Page 1111–1116 It is odd that both lineages seem to date back to a maximum of 200,000 to 300,000 years ago. Prior to these research projects it was theorized that this branch of study could determine which hominins the modern-humans evolved from. With a date of only 260,000 years ago, it cannot point to the origin of humanity, or can it?

References   [ + ]

1. C. William Birky (2008) “Uniparental inheritance of organelle genes” Current Biology, Volume 18, Number 16, Pages R692–R695
2. N. A. Johnson (2007) Darwinian Detectives: Revealing the Natural History of Genes and Genomes, Page 92
3. R. Lewin (1987) “The unmasking of mitochondrial Eve” Science, Volume 238, Number 4823, Pages 24–26
4. J. Wainscoat (1987) “Out of the garden of Eden” Nature, Volume 325, Number 6099, Page 13
5. Rebecca L. Cann et al. (1982) “Evolution of human mitochondrial DNA: a preliminary report” Progress in Clinical Biological Research, Volume 103, Part A, Pages 157–165
6. Pedro Soares et al (2009) “Correcting for Purifying Selection: An Improved Human Mitochondrial Molecular Clock and its Supplemental Data” The American Journal of Human Genetics, Volume 84, Issue 6, Pages 740–759
7. Eran Elhaik et al. (2014) “The ‘extremely ancient’ chromosome that isn’t: a forensic bioinformatic investigation of Albert Perry’s X-degenerate portion of the Y chromosome” European Journal of Human Genetics, Volume 22, Number 9, Page 1111–1116