Minimum oxygen threshold for the origin of animal multicellularity

Determine the minimum environmental oxygen level, expressed relative to present atmospheric levels, required to permit the evolutionary origin of multicellularity in animals (Metazoa), by integrating comparative physiology, experimental evolution, and paleo-oxygen reconstructions.

Background

The paper argues that major evolutionary transitions required for human existence were gated by changing global environments, especially oxygen. While experimental and theoretical work has suggested various thresholds, the specific lower oxygen requirement for the evolutionary emergence of animal multicellularity remains unresolved.

Clarifying this threshold is essential to test whether environmental constraints, rather than intrinsic improbability, explain the timing of animal origins and to refine models predicting when similar transitions could occur on other planets.