Applicability of yeast multicellularity experiments to animal origins

Assess the applicability of oxygen-suppression results from experimental evolution of snowflake yeast to the evolutionary origin of animal multicellularity, accounting for ancestral differences such as flagellation and facultative aerobiosis in the unicellular ancestors of animals.

Background

Experimental evolution with snowflake yeast has shown that oxygen can suppress macroscopic multicellularity, suggesting environmental oxygen may modulate multicellular evolution. However, the unicellular ancestors of animals likely had traits (flagella, facultative aerobiosis) that differ substantially from yeast, complicating direct inference.

Resolving the relevance of yeast results to animal origins is important for evaluating hypotheses that low but nonzero oxygen levels in the Proterozoic inhibited early animal multicellularity.

References

However, the applicability of these results to the origin of animal multicellularity is unclear, since the single-celled ancestors of animals – unlike yeast – likely possessed flagella (whip-like structures that generate water currents) (106) and were facultative aerobes (capable of metabolizing with and without O ) (256).

— A reassessment of the "hard-steps" model for the evolution of intelligent life (2408.10293 - Mills et al., 19 Aug 2024) in Section 'Increasing habitat diversity over geologic time'