Improved calibration of the human mitochondrial clock using ancient genomes

Area of Science:

• Evolutionary biology
• Population genetics
• Molecular evolution

Background:

• Accurate DNA substitution rates are essential for understanding species evolution and past demographics.
• Previous human substitution rate estimates show significant variation, hindering reliable conclusions.
• Divergence from root or internal nodes in phylogenetic trees are traditional calibration methods.

Purpose of the Study:

• To clarify discrepancies in human substitution rate estimates.
• To compare the reliability of node-based versus tip-based calibration methods using ancient DNA.
• To establish a more consistent method for estimating human mitochondrial DNA substitution rates.

Main Methods:

• Compiled a dataset of 350 ancient and modern human complete mitochondrial DNA genomes.
• Estimated substitution rates using calibrations based on both dated nodes and tips.
• Analyzed sequence panels and methodologies to identify sources of estimate variation.

Main Results:

• Estimates based on individual dated tips were significantly more consistent than those based on nodes.
• The study identified methodological variations as a cause for differences in previous estimates.
• Ancient mitochondrial DNA tip calibration offers a more direct and reliable approach.

Conclusions:

• Tip-based calibration using ancient DNA provides more reliable human substitution rate estimates.
• Node-based calibration methods introduce greater variability and uncertainty.
• Consistent substitution rate estimates are crucial for accurate human evolutionary and demographic studies.