Author: Tyler Vazquez
Editors: Kira Tian and Cynthia Zhang
Artist: Jiaqi Fan
It is common knowledge that the first humans evolved from primates in Africa in the history of the world. This is largely agreed upon by all people, regardless of their religious beliefs or their hypotheses on biogenesis. Something that isn’t widely discussed, however, is Mitochondrial Eve. Gathering her namesake from the Biblical Eve, this woman likely roamed the Makgadidaki wetland in the modern-day Kalahari. This extinct wetland is now roamed by the San people, a nomadic group.
Well, who was Mitochondrial Eve? The truth is that we don’t really know. Archeologists have found no evidence of Eve’s remains or life story. All we know about her is when she lived: around 200,000 years ago. She was humanity’s most recent common ancestor (MRCA), meaning that every person who lived after her is related to her. It should, however, be noted that she was not the first human, but instead the last human that all humans share lineage with. We don’t know what she looked like, sounded like, or even her real name.
So, how do MRCA’s work? Every organism that lived within the last 3.5 billion years shares a common ancestor, known as our Last Universal Common Ancestor. This organism was likely an anaerobic and autotrophic microbe living in the ocean 3.5-3.8 billion years ago, gathering energy from the iron-and-sulfur-rich hydrothermal vents around it. It is important to note that this is not the first organism, but the last one that every organism after it shares a lineage with genetically.
As humans, we share very similar mitochondrial genetic material because the mitochondria and its genetic material are only passed down matrilineally (from mother to offspring). This is due to the process of fertilization, where the mitochondria of the father’s sperm (located in the “tail”) break off to fit into the egg. Therefore, with only one copy of all our mitochondrial genes compared to two per nucleic gene, there would not be much variation or diversity within the gene pool. This makes those subtle variations that stem from mitochondrial mutations easy to track within a population. For example, if there is a slight gene mutation in a mother’s mitochondrial genes in an egg, then this can be tracked generations later in her offspring and descendants as a direct lineage. When genes such as the L0 gene were traced in southern African nomadic people from today to over 200,000 years ago, we can conclude that someone from this region bore children that would be our ancestors.
This analysis of mitochondrial DNA was conducted by Vanessa Hayes of the Garvan Institute of Medical Research, with 1200 African nomadic subjects. This pinpoints, or at least approximates, that the woman who shares a lineage with humans was in Southern Africa. Nevertheless, this raises questions about Chromosomal Adam, or the male, the ancestor to whom all males have a common lineage. He likely had lived in West Africa, not South Africa. Though fascinating, it raises the question of who he was and whether Mitochondrial Eve was his ancestor.
Regardless, our quest for discovering the origins of life, especially as it pertains to humanity, is only just beginning. Through advancements in genetics, discovering our lineage will likely stretch onward for decades.
Citations:
Cooper, K. (2018, December 18). Looking for LUCA, the last universal common ancestor.
Retrieved September 21, 2020, from https://phys.org/news/2018-12-luca-universal-
Gahl, W., MD. (n.d.). Mitochondrial DNA. Retrieved September 21, 2020, from https://www.genome.gov/genetics-glossary/Mitochondrial-DNA
Mitochondrial DNA - Genetics Home Reference - NIH. (2020, August). Retrieved September
21, 2020, from https://ghr.nlm.nih.gov/mitochondrial-dna
Specktor, B. (2019, October 28). Scientists Think They've Found 'Mitochondrial Eve's' First Homeland. Retrieved September 21, 2020, from