Defining Mitochondrial Eve
Mitochondrial Eve is the name given to the most recent common matrilineal ancestor of all living humans. She is the female ancestor from whom all humans alive today descend, tracing back exclusively through their mothers, and through their mothers' mothers, and so on. It's crucial to understand that she was not the only woman alive at her time, nor was she the "first woman," but rather the only one whose unbroken maternal lineage continues to the present day.
The Role of Mitochondrial DNA (mtDNA)
Her existence is inferred from studies of mitochondrial DNA (mtDNA), a small circular chromosome found in the mitochondria of cells, inherited almost exclusively from the mother. Unlike nuclear DNA, mtDNA does not undergo recombination, meaning it changes only through mutations that accumulate over generations. This makes it an ideal genetic marker for tracing maternal ancestry deep into the past without interference from paternal genes.
Tracing Human Origins and Migration
By comparing mtDNA sequences from diverse populations worldwide, scientists can construct a phylogenetic tree that maps the maternal lineage of humanity. This tree converges to a single ancestral mtDNA sequence, attributed to Mitochondrial Eve. Her geographic origin is estimated to be in East Africa, roughly 150,000 to 200,000 years ago, providing strong genetic evidence for the "Out of Africa" theory of human migration.
Common Misconceptions and Significance
A common misconception is that Mitochondrial Eve was the only female alive or the first female human. In reality, many other women lived during her time, but their direct maternal lines eventually died out. Her significance lies in providing a powerful genetic anchor for understanding the timeline and geographical origins of our species, helping to illuminate the shared genetic heritage of all humans.