Mitochondrial COII sequences and modern human origins

Area of Science:

• Human evolutionary genetics
• Mitochondrial DNA analysis
• Molecular anthropology

Background:

• The multiregional hypothesis proposes modern humans evolved in multiple regions simultaneously.
• Estimating the emergence time of the human mitochondrial ancestor is crucial for understanding human origins.
• Mitochondrial DNA (mtDNA) is a valuable tool for tracing maternal lineage and evolutionary history.

Purpose of the Study:

• To measure human mitochondrial sequence variability in the cytochrome oxidase subunit II (COII) gene.
• To estimate the existence time of the human common ancestral mitochondrial type.
• To evaluate the compatibility of mtDNA data with the multiregional hypothesis.

Main Methods:

• Sequencing of the COII gene in five humans and three chimpanzees (Pan paniscus and P. troglodytes).
• Analysis of COII sequences alongside data from the ND4-5 mitochondrial region.
• Estimation of divergence times using third codon position (class 1) sequence data and coalescent times.

Main Results:

• A relative divergence date for the human mitochondrial ancestor was estimated at 1/27th of the human-chimpanzee divergence time.
• Assuming a 6 Mya human-chimpanzee divergence, the human mitochondrial ancestor is placed at 222,000 years ago.
• The mean coalescent time from combined mtDNA data was estimated at 298,000 years (95% CI: 129,000-536,000 years).

Conclusions:

• The estimated ages for the human mitochondrial ancestor (222,000-298,000 years) are not compatible with a 1-Myr-old ancestor.
• The mtDNA sequence data from COII and ND4-5 regions do not support the multiregional hypothesis for modern human emergence.
• These findings suggest a more recent origin for the modern human mitochondrial lineage than proposed by some models.