430: Proterozoic Rise: Steady Diversification of Crown Eukaryotes

Sandin MM et al., Proceedings of the National Academy of Sciences - Molecular clocks and diversification models applied to a 75,975-OTU rDNA dataset, including long-read environmental sequences and 77 fossil calibrations, indicate crown-group eukaryotes diversified steadily from the mid‑Proterozoic with Archaeplastida dominating early diversity. Key terms: eukaryote evolution, Proterozoic diversification, Archaeplastida, molecular clock, environmental sequencing. Study Highlights:The study assembled 75,975 nonredundant rDNA OTUs combining long-read environmental metabarcoding and reference sequences and calibrated 32 timetrees with 77 fossil constraints. Molecular dating places LECA at ~1775 Ma and finds most eukaryotic supergroups originating across the Mesoproterozoic. Diversification analyses (ClaDS, BAMM) show steady accumulation of crown-group diversity through the Proterozoic, with Archaeplastida exhibiting an early rapid diversification likely tied to plastid endosymbiosis. Results suggest crown eukaryotes were ecologically and taxonomically diverse long before clear crown-group fossils appear. Conclusion:Integrating extensive environmental sequencing with molecular dating and diversification models reveals that crown-group eukaryotes were diversifying steadily from the mid‑Proterozoic, overturning the notion of a biologically stagnant “boring billion” and indicating early ecological interactions and endosymbioses drove diversification. Music:Enjoy the music based on this article at the end of the episode. Article title:Environmental phylogenetics supports a steady diversification of crown eukaryotes starting from the mid-Proterozoic First author:Sandin MM Journal:Proceedings of the National Academy of Sciences DOI:10.1073/pnas.2600283123 Reference:Sandin MM, Burki F, Cohen PA, Morlond H (2026) Environmental phylogenetics supports a steady diversification of crown eukaryotes starting from the mid-Proterozoic. PNAS 123(29):e2600283123. doi:10.1073/pnas.2600283123 License:This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/by/4.0/ Support:Base by Base is independent and ad-free — no sponsors, no paywall. If an episode was worth your time, chip in and keep the papers audited and the original songs coming:❤️ Support monthly: https://buy.stripe.com/cNifZhclVebvagk2JDgEg01☕ One-time donation: https://donate.stripe.com/7sY4gz71B2sN3RWac5gEg00 More at basebybase.com On PaperCast Base by Base you'll discover the latest in genomics, functional genomics, structural genomics, and proteomics. Episode link: https://basebybase.com/episodes/environmental-phylogenetics-steady-diversification-crown-eukaryotes QC:This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-23. QC Scope:- article metadata and core scientific claims from the narration- excludes analogies, intro/outro, and music- transcript coverage: Audited transcript segments covering LECA dating and molecular clock; environmental sequencing (OTUs and 18S-28S rDNA); Archaeplastida endosymbiosis and early diversification; Proterozoic diversification dynamics and the 'boring billion' reinterpretation; predator–prey dynamics and fossil evidence; and limitations/samp- transcript topics: LECA dating and molecular clock; Environmental metabarcoding and OTU dataset (75,975 OTUs); Archaeplastida diversification and plastid endosymbiosis; Proterozoic diversification vs. 'boring billion' narrative; Predation, defense, and ecosystem dynamics (fossil evidence); Sampling limitations and diversification modeling (ClaDS, BAMM) QC Summary:- factual score: 10/10- met...