LPL Colloquium- Stepping into the Past: Recreating Ancient Biology in the Laboratory

Uniformitarianism has been applied with great success in extrapolating the chemical and physical history of geologic materials on the early Earth. However, its limits are quickly reached when dealing with biological organisms and structures. The relationships between objects in physics and chemistry are essentially immutable, whereas the very property that has made life so successful is its mutability. Interpretations of ancient biogeochemical evidence are valid under the assumption that the enzymes responsible for mediating those biogeochemical interactions have remained functionally conserved over Earth’s history. Genetic mutability must be addressed, however, if we are to draw connections between past environments and ancient enzymes that have evolved over billions of years. Though admittedly a reductionist perspective, enzymes can offer a practicable target for molecular resurrection studies. By relating ancestral enzyme properties to preserved biosignatures, we may constrain aspects of the ancient environment in which they functioned, as well as identify instances within biomolecular evolutionary trajectories that may be tied to significant biogeochemical events. To what extent can we infer whether extant biomolecules and organisms can serve as effective proxies for their ancestors in deep time? How do we detect the circumstances or assumptions when they are in fact poor proxies? And when we suspect that they are poor proxies, can we modify extant organisms to behave more like their predecessors – even if it is only in very narrow ways that reconstructing ancient biological systems demands? In this talk I will provide a survey of these recent efforts of my laboratory, in an attempt to provide a reasoned assessment of areas of success and common pitfalls associated with approaches that are built upon inferring ancient genetic sequences and our ability to apply what we learn in the laboratory to understand the origins of life on Earth as well as its potential presence elsewhere in the Universe.