Final answer:
The 'Mitochondrial Eve' hypothesis suggests all modern humans can trace their ancestry back to a single woman who lived in Africa around 200,000 years ago, based on analysis of mitochondrial DNA. This supports the 'Out of Africa' model, indicating that Homo sapiens originated in Africa before spreading globally.
Step-by-step explanation:
The theory that states humans originated in Africa from a single woman is often referred to as the "Mitochondrial Eve" hypothesis. Genetic research indicates that all humans can trace their ancestry back to this one woman through our mitochondrial DNA (mtDNA), which is passed down from mother to offspring. This woman, named 'Eve' for convenience, is not the first human female but rather our most recent common matrilineal ancestor, who lived approximately 200,000 years ago in Africa.
Scientists have gathered evidence from human genomes showing that all people living outside of Africa have genomic connections to people within Africa, suggesting a single point of origin for modern humans. Furthermore, the genetic diversity found in Africa is not completely represented outside the continent, supporting the idea of an African origin for Homo sapiens. Mutations in mtDNA occur at a relatively constant rate, allowing researchers to map out our evolutionary journey from this common ancestor.
The "Out of Africa" model of human evolution, which posits that modern humans emerged first in Africa and later spread across the world, is the most widely accepted explanation for these genetic findings. This is contrasted with the "multiregional evolution model", which suggests multiple origins of Homo sapiens from Homo erectus in different parts of the world. However, the African origin theory, supported by more robust genetic evidence, has become the prevailing consensus among scientists.