Exact Distribution of Divergence Times from Fossil Ages and Tree Topologies

Area of Science:

• Evolutionary Biology
• Paleontology
• Computational Biology

Background:

• Phylogenetic trees often rely on fossil ages for temporal information, with divergence times frequently unknown.
• Accurate divergence time estimation is crucial for understanding evolutionary history and calibration points.

Purpose of the Study:

• To develop a method for computing exact probability distributions of divergence times using the Fossilized Birth-Death model.
• To estimate the divergence time of Amniota (mammal/bird ancestor) with associated uncertainty.

Main Methods:

• Utilized the Fossilized Birth-Death model incorporating speciation, extinction, and fossilization rates.
• Developed a novel computational method to derive probability distributions for divergence times from fossil ages.
• Applied the method to estimate the age of the Amniota divergence.

Main Results:

• Provided a method to compute the exact probability distribution for any divergence time in a phylogenetic tree.
• Estimated the Amniota divergence time to be between 322 and 340 million years ago (Ma).
• This age is older than the commonly assumed 310-315 Ma.

Conclusions:

• The developed method offers a robust way to quantify uncertainty in divergence time estimation.
• The findings challenge previous assumptions about the Amniota divergence age, suggesting an earlier origin.
• This work provides a new tool for paleontological and evolutionary dating.