The blueprint of our body lies within our DNA – the genetic material we inherit from our parents. It is common knowledge that equal parts of this DNA come from our mother and father. A single strand of someone’s DNA can not only be used to determine their biological parents but can also point to their ancestry. This is called ancestry tracing.
Many platforms, such as “ancestry.com” and “23andMe”, have made genomic DNA analysis available and accessible, helping determine your genetic predisposition to diseases as well as your carrier status for certain genetic diseases. They can also help quench your general curiosity regarding your ancestral history. However, the latter may not be accurate as they claim, as analyzing genetic information over an exceptionally large number of generations can be very challenging. Since each child has two parents, the amount of data doubles every generation you include in the analysis. For example, you have two parents, four grandparents, eight great-grandparents and so on. For this reason, ancestry tracing becomes quite tedious and leads to an excess of information when you are trying to look at hundreds and thousands of generations, which ultimately leads to inaccuracy and inconclusive results.
This is where people have turned to a special type of maternal ancestry tracing that is simpler yet informative, the mitochondrial DNA (mtDNA) tracing. Contrary to conventional DNA tracing, which uses nuclear DNA information that is equal parts inherited from maternal and paternal DNA, mitochondria consist solely of genetic material derived from the mother.
Through mtDNA tracing, scientists like Allan Wilson have attempted to pinpoint the first human female by drawing a line through generations of mothers to our most recent common female ancestor – the Mitochondrial Eve. She is believed to have lived around 200,000 years ago in what’s now Africa. Importantly, all currently living humans are descendants of her.
But is the Mitochondrial Eve truly the most recent common ancestor of the entire human race? Another group of scientists says no and thinks this is an overinterpretation of molecular evolution data. Soon after the proposal of the idea of mitochondrial Eve, F.J. Ayala, and others argued that such a retrospective method of looking at ancestral genes was not the best representation of the truth. They highlighted that it is crucial to acknowledge that Eve was not the only female of her time. There could be other female ancestors at this time; however, unlike Mitochondrial Eve, none have a direct matrilineal descent traceable to all humans living today. This might be because being childless or only bearing sons stopped their maternal ancestry line in history. In addition, the amount of mtDNA that current humans have inherited from the Mitochondrial Eve is exceptionally minute, about 400,000th of the total DNA in a cell. The rest of the DNA, namely nuclear DNA, can be from maternal and paternal lines; hence it includes other maternal ancestor genes. This makes it hard to pinpoint the first “real” common female ancestor using mtDNA alone, as we might potentially carry more genes from females other than the identified Mitochondrial Eve. Moreover, the tree of evolution is not segmented. Evidence has suggested continuous interbreeding between early human species like the Neanderthals and Denisovans, making it unrealistic to pinpoint the true female “human” ancestor.
Taken together, this evidence has raised some important questions – did Mitochondrial Eve truly exist? Or is she just a mythical creature conjured up by scientists who unknowingly oversimplified some very complex data? What do you think?
References
1. https://www.scientificamerican.com/article/how-do-researchers-trace/
2. https://www.23andme.com/en-ca/
4. https://whoareyoumadeof.com/blog/how-far-back-can-you-go-with-genealogy/
5. https://www.wondriumdaily.com/mitochondrial-eve-the-mother-of-all-human-beings/
6. Hössjer, Ola, and Ann Gauger. “A single-couple human origin is possible.” BIO-Complexity 2019 (2019).
7. Ayala, Francisco J. “The Myth of Eve: Molecular Biology and Human Origins: FJ Ayala.” Science 270.5244 (1995): 1930-1936.
8. Hawks, John, et al. “Population bottlenecks and Pleistocene human evolution.” Molecular biology and evolution 17.1 (2000): 2-22.
9. Ayala, Francisco J., and Ananias A. Escalante. “The evolution of human populations: a molecular perspective.” Molecular Phylogenetics and Evolution 5.1 (1996): 188-201.
Manjula Kamath
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