This event will take place on Friday October 2nd, 2026, at the Department of Zoology (Main Lecture Theatre), University of Cambridge, Downing Street CB2 3EJ, 12:30 - 18:30. There will be no posters, ...

This study introduces iChIP2, a low-input chromatin immunoprecipitation followed by sequencing method that profiles histone post-translational modifications (hPTMs) simultaneously across diverse eukar...

Cis-regulatory elements, such as enhancers, play an essential role in coordinating gene expression programs during cellular transitions. As such, substantial efforts have been made to characterize enh...

Nature - A unicellular relative links aggregative multicellularity to animal origins

Experiments in the cnidarian Nematostella vectensis show a role of gene body methylation in transposable element suppression and that epigenetic inheritance is constrained by chromatin context and tra...

In this Review, Abergel et al. overview infection cycles across the Nucleocytoviricota phylum, highlighting shared mechanisms and lineage-specific features spanning viral entry, viral factory formatio...

Complex multicellularity has evolved in just five lineages (animals, plants, brown algae, red algae, and fungi) and in each case, these organisms develop clonally and are obligately multicellular. While prior work has shown that clonal development plays a critical role in the evolution of complex multicellularity, none has disentangled this from the impact of obligate vs facultative multicellular life cycles. Here we use experimental evolution with engineered snowflake yeast ( Saccharomyces cerevisiae ) to directly test how life cycle structure affects multicellular adaptation. We created isogenic strains capable of switching between unicellular and clonal multicellular phases, then evolved populations for 192 days under obligately multicellular, facultatively multicellular, and obligately unicellular regimes. Obligately multicellular populations rapidly evolved larger size, primarily driven by a whole genome duplication, in all five replicates. Facultative populations showed dramatically constrained evolution, with tetraploidy evolving in only 2/10 facultative populations despite experiments demonstrating that it is strongly beneficial across the full life cycle. Mathematical modeling reveals the mechanistic basis for this constraint: facultative life cycles create establishment barriers through two population genetic effects. Group formation dramatically reduces the number of units of selection, making beneficial multicellular mutations vulnerable to drift. This asymmetry in population size between life cycle phases also allows cell-level selection to overpower group-level selection, eliminating mutations that provide group-level benefits but carry cell-level costs. These findings demonstrate that obligate multicellularity circumvents fundamental population genetic barriers to collective-level adaptation, helping explain why complex multicellularity has evolved exclusively in obligately multicellular lineages, and suggesting similar constraints may operate in other evolutionary transitions in individuality. ### Competing Interest Statement The authors have declared no competing interest. U.S. National Science Foundation, https://ror.org/021nxhr62, DEB-1845363 Howard Hughes Medical Institute Gilliam Fellowship National Science Foundation Graduate Research Fellowship