A revised timescale for human evolution based on ancient mitochondrial genomes.

Area of Science:

• Genetics
• Paleogenomics
• Human Evolution

Background:

• Recent nuclear DNA mutation rate analyses suggest human evolutionary events occurred earlier than previously estimated.
• These new estimates challenge established timelines for human population divergence.

Purpose of the Study:

• To directly estimate the human mitochondrial substitution rate using ancient DNA.
• To recalibrate human divergence times and assess their consistency with previous estimates.

Main Methods:

• Utilizing mitochondrial genome sequences from ten ancient modern humans with secure dates (spanning 40,000 years).
• Applying these ancient samples as calibration points for the mitochondrial clock.

Main Results:

• The study provides a direct estimate of the mitochondrial substitution rate.
• Mitochondrial divergence times align with earlier estimates based on fossil or archaeological data.
• The separation of non-Africans from sub-Saharan African mitochondrial DNA (haplogroup L3) is estimated to have occurred less than 62-95 kya.

Conclusions:

• Mitochondrial DNA (mtDNA) provides valid upper bounds for population divergence times, despite potential biases.
• The findings exclude the older divergence dates suggested by recent nuclear genome de novo mutation rate estimates.
• This research supports established timelines for early human population movements out of Africa.