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