Timing of the emergence of LECA relative to early eukaryotic fossils

Determine whether the last eukaryote common ancestor (LECA) emerged hundreds of millions of years before or after the oldest eukaryotic-grade fossils (1.63–1.67 Ga), by integrating fossil, phylogenetic, and molecular clock evidence to establish the completion time of eukaryogenesis.

Background

The authors highlight persistent uncertainty in the eukaryotic fossil record concerning when LECA arose, which marks the completion of eukaryogenesis. Competing scenarios place LECA either substantially before or after the oldest total-group eukaryote fossils.

Resolving LECA’s timing is critical for testing models that link evolutionary milestones to environmental thresholds rather than intrinsic improbability.

References

Specifically, it remains unclear whether LECA emerged hundreds of millions of years before the oldest eukaryotic-grade fossils (1.63-1.67 billion years ago, or Ga), or hundreds of millions of years after (to use the two end-member scenarios) (86).

— A reassessment of the "hard-steps" model for the evolution of intelligent life  (2408.10293 - Mills et al., 2024) in Figure 1 caption, 'Figure Captions, Tables, and Table Captions'