James Howell
October 29, 2021
Zoom recording
Abstract:
In the past twenty years, the number of confirmed exoplanets has jumped 150 fold (< 40 before 2000, > 4,800 in 2021) and that total is likely to continue to grow rapidly. Informed efforts to narrow the search for biosignatures and technosignatures to most-likely “habitable zones” are thus increasingly required. Relevant to this goal, there is a long tradition of efforts to build parametric frameworks describing likely scenarios for the necessary sequence of (1) emergence of life, (2) emergence of complex life, and (3) emergence of intelligence leading to technological civilization. These attempts have been guided by biology (e.g. “evolutionary transitions”) or physical and statistical first principles (“hard steps”). Both categories of concepts provide preliminary analytical tools, but both suffer from fundamental conceptual and practical flaws. We will discuss a framework for analysis that proceeds from the contemporary biological consensus on the natural history of this biosphere, and attempts to generalize to (very) different planetary conditions.