How deep is history? A barcoded replay of multicellularity across branching evolutionary timelines

Khey & Travisano (2025) demonstrated strong historical contingency in yeast evolving multicellularity and reversion, while Wang et al. (2024) revealed convergent genetic routes across divergent yeasts under settling selection. This project creates a controlled phylogeny of barcoded yeast lineages that branch at predefined generations and then experience alternating selection regimes (settling vs spatially structured growth) to quantify how the timing of early adaptive steps constrains later evolutionary routes. It uses CRISPR-integrated lineage barcodes and retron-based mutational recorders to track sublineage histories. At each branching point, lineages are archived and later replayed in both environments. Whole-population and clone sequencing map which multicellularity routes are accessible as a function of history depth, measuring architecture differences, pleiotropic costs, and re-evolution rates. This designed history experiment manipulates timing and depth of divergence rather than inferring contingency post hoc, aligning with calls to quantify historical contingency over hundreds of generations. It extends convergent findings by testing when convergence fails and whether early mutations canalize later outcomes, specifically testing if the ACE2-dominant route is history-dependent or robust. The impact is a quantitative map of contingency versus convergence for a major evolutionary transition, informing how early evolutionary decisions set long-term constraints relevant to cancer evolution, antibiotic treatment sequences, and adaptive management.

References:

1. Historical effects during experimental evolution of multicellularity in Saccharomyces cerevisiae.. Joleen Khey, Michael Travisano (2025). Evolution; international journal of organic evolution.
2. Genomic sequencing reveals convergent adaptation during experimental evolution in two budding yeast species. Pu Wang, William W Driscoll, M. Travisano (2024). Communications Biology.