Life-hostile conditions in the early universe can increase the present-day odds of observing extragalactic life

TL;DR

This paper argues that hostile conditions in the early universe may paradoxically increase the likelihood of observing extragalactic life today, due to the displacement of habitable sites by expanding civilizations.

Contribution

It introduces an anthropic model showing how early universe dangers can lead to higher present-day extragalactic life estimates through civilization expansion effects.

Findings

Early universe dangers can increase observable extragalactic life.

Civilization expansion displaces potential life sites, affecting life prevalence estimates.

Stationary advanced life does not produce this effect.

Abstract

High-energy astrophysical events that cause galaxy-scale extinctions have been proposed as a way to explain or mollify the Fermi Paradox, by making the universe at earlier times more dangerous for evolving life, and reducing its present-day prevalence. Here, we present an anthropic argument that a more dangerous early universe can have the opposite effect, actually increasing estimates for the amount of visible extragalactic life at the present cosmic time. This occurs when civilizations are assumed to expand and displace possible origination sites for the evolution of life, and estimates are made by assuming that humanity has appeared at a typical time. The effect is not seen if advanced life is assumed to always remain stationary, with no displacement of habitable worlds.