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The forces influencing evolutionary adaptations are undoubtedly governed by historic constraints: an organism’s past constrains its future. To what degree, however, do prior mutations and ancestral phenotypes shape future evolutionary pathways? Did life in the past function or evolve similarly to life today? Did the biology of ancestral organisms, the functions of their proteins or other factors inherently limit their ability to evolve into modern forms?

This project asks whether adaptive pathways are inherently deterministic, dominated by internal or external controlling or limiting processes, or highly contingent upon chance events such that very different evolutionary outcomes may arise from identical initial conditions. Little is currently known about how prior evolutionary history shapes future evolutionary trajectories, or a lineage’s capacity to produce adaptive variation. Our approach is to systematically investigate how prior history affects the evolution of modern organisms. We individually engineer modern bacterial genomes with a series of inferred ancient genetic sequences and then experimentally evolve the ancient-modern hybrid bacteria in the laboratory to examine how the ancient genes and modern genome adapt to each other. The work draws upon tools from a variety of disciplines such as paleogenetics, synthetic biology, experimental evolution, whole-genome sequencing as well as proteomics, and demonstrates a new approach with which to probe historical pathways of evolution, as well as to connect genotype and phenotype.


Key Papers


Functional Constraints on Replacing an Essential Gene with Its Ancient and Modern Homologs. Read Paper >>>

Experimental Evolution of Escherichia coli Harboring an Ancient Translation Protein. Read Paper >>>

Rolling the Dice Twice…. Read Paper >>>


Recent Highlights


The John Templeton Foundation highlights our work on replaying evolution.


View the NOVA educational curriculum on the origins of life and reconstructing evolution that we helped develop for PBS. 


Philosophical implications of our molecular time-travel work “Future Shaped by Pasts that Might Have Been,” a published conversation with afrofuturist Ytasha Womack.


Key Collaborators

Sergey Kryazhimskiy (UCSD)

NASA Astrobiology Reliving the Past Node CAN7

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