5.4.1 Mitochondrial Eve

Begun in 1990 and concluding in 2003, the Human Genome Project was an ambitious international effort that sequenced about 99 percent of the human genome with an accuracy of 99.99 percent. Genetics has thus far largely confirmed the Out of Africa theory, which proposes that early humans left Africa around 100,000 years ago and migrated to diverse areas of the world. When early humans left Africa and moved into Europe, they not only lived alongside but also interbred with non-African species such as the Neanderthal, who were already inhabiting the region.

Molecular anthropologists have an interest in determining when living human populations began diverging from one another. This has been difficult to do using nuclear DNA because it mutates much too slowly for measurable accumulations to occur in 200,000 years. Many of the genetic studies that have been conducted are thus based on genetic material carried in the mitochondria (mtDNA), which are passed on maternally. There is no recombination in mtDNA, so unless the mitochondria carries a novel mutation, a child has exactly the same mitochondrial genes as its female genetic contributor (which may be its mother, egg donor, or someone in a similar genetic relationship). The mitochondria of every living person is a copy, modified only by rare mutations, of the mitochondria passed down via matrilineal descent from a population in our ancient past. This population is referred to as Mitochondrial Eve or mtMRCA (mitochondrial most recent common ancestor), believed to have lived in southern Africa 100,000–200,000 years ago.

As discussed in Chapter 4, the longer ago two populations share a common ancestor, the more time there is for mutations to occur and for adaptations and change to take place. Although genetic variation is small among the world’s human populations, it is greatest in Africa. This indicates that the human populations in Africa have the longest established genetic lineage. While multiple hypotheses exist as to human origins and new evidence could change the current views, the consensus is an Out of Africa model traced back to the matrilineal descent of a population living in Africa about 200,000 years ago.