eLife: latest articles by subject

Heterozygote advantage cannot explain MHC diversity, but MHC diversity can explain heterozygote advantage

jcherry@ncbi.nlm.nih.gov (Joshua L Cherry) — Mon, 13 Jul 2026 00:00:00 +0000

Several theoretical studies have concluded that heterozygote advantage makes at most a minor contribution to MHC diversity. Siljestam and Rueffler (2024) recently presented models in which heterozygote advantage alone can lead to realistically high diversity. Here I argue that heterozygote advantage cannot by itself explain MHC diversity, and that its contribution to diversity is unlikely to be large in most species. I first show that the high diversity reported by Siljestam and Rueffler is so sensitive to parameter values that the underlying phenomenon cannot explain the widespread diversity of MHC genes. I then consider a fundamental problem with explaining MHC diversity by heterozygote advantage alone: selective forces that favored heterozygotes would lead to the evolution of haplotypes having much higher fitness when homozygous, diminishing or eliminating heterozygote advantage. Diversity maintained by another force, however, might bring about adaptation to the more common heterozygous state at the expense of homozygous fitness. Thus, substantial heterozygote advantage may arise as a consequence of MHC diversity.

Correction: Asymmetrical diversification of the receptor-ligand interaction controlling self-incompatibility in Arabidopsis

Thu, 09 Jul 2026 00:00:00 +0000

Pervasive relaxed selection on spermatogenesis genes coincident with the evolution of polygyny in gorillas

denard@arizona.edu (David Enard) — Tue, 07 Jul 2026 00:00:00 +0000

Gorillas have a polygynous social system in which the highest-ranking male has almost exclusive access to females and sires most of the offspring in the troop. Such behavior results in a dramatic reduction of sperm competition, which is ultimately associated with numerous traits that cause low efficacy of gorilla spermatogenesis. However, the molecular basis behind the remarkable erosion of the gorilla male reproductive system remains unknown. Here, we explored the genetic implications of the polygynous social system in gorillas by testing for altered selection intensity across 13,310 orthologous protein-coding genes from 261 Eutherian mammals. We identified 578 genes with relaxed purifying selection in the gorilla lineage, compared with only 96 that were positively selected. Genes under relaxed purifying selection in gorillas have accumulated numerous deleterious amino acid substitutions; their expression is biased towards male germ cells, and they are enriched in functions related to meiosis and sperm biology. We tested the role of gorilla relaxed genes previously not implicated in male reproductive function using the Drosophila model system and identified 41 novel spermatogenesis genes required for normal fertility. Furthermore, by exploring exome/genome sequencing data of infertile men with severe spermatogenic impairment, we found that the human orthologs of the gorilla relaxed genes are enriched for loss-of-function variants in infertile men. These data provide compelling evidence that reduced sperm competition in gorillas is associated with relaxed purifying selection on genes related to male reproductive function. The accumulation of deleterious mutations in these genes likely provides the mechanistic basis behind the low efficacy of gorilla spermatogenesis and uncovers new candidate genes for human male infertility.

Experimental evolution to thermal stress indicates climate resilience in a cosmopolitan arthropod

sjyou@fafu.edu.cn (Fengluan Yao) — Tue, 30 Jun 2026 00:00:00 +0000

Adaptive evolution enables species to survive and thrive under changing environmental conditions. In the face of accelerating global climate change, thermal stress represents a major challenge to the persistence of terrestrial arthropods. Understanding the genetic mechanisms underlying thermal adaptation is therefore critical for predicting species’ evolutionary potential and future success. Here, we combine experimental evolution, phenotypic assays, and multi-omics analyses to investigate the adaptive responses of the diamondback moth (Plutella xylostella), a globally destructive pest of cruciferous crops, to contrasting thermal environments. Populations evolved under hot (32 °C/27 °C) and cold (15 °C/10 °C) regimes exhibited distinct life history and fitness traits relative to those maintained under favorable conditions (26 °C). The hot strain showed accelerated development, higher fecundity, and increased survival under extreme heat, while the cold strain exhibited lower supercooling and freezing points, indicating enhanced cold hardiness. Integrated transcriptomic and metabolomic analyses revealed extensive transcriptional reprogramming and convergent metabolic adjustments, notably a reduction in lipid metabolism to conserve energy under thermal stress. Crucially, non-synonymous mutations in PxSODC enhance superoxide scavenging efficiency, enabling effective oxidative stress management at lower gene expression levels. Furthermore, we identified epigenetic regulation via DNA methylation as a key mediator of this thermal tolerance. Together, these coordinated mutational, epigenetic, and metabolic insights highlight this arthropod’s capacity for global dispersal and likely persistence under climate change, establishing a framework for understanding equivalent effects in other species.

Brawn before bite in endemic Asian eutherian mammals after the end-Cretaceous extinction

zjt@berkeley.edu (Qian Li) — Tue, 30 Jun 2026 00:00:00 +0000

The first 10 million years (Myr) following the Cretaceous-Paleogene (K-Pg) mass extinction marked a period of global greenhouse conditions and dramatic rise of placental mammals. Because ~80% of known terrestrial sections capturing post-K-Pg mammal recovery come from North America, a substantial knowledge gap exists in the tempo and mode of recovery in Asia, where only 3% of global sites are located and most contain species found nowhere else. We show that isolated Paleocene eutherian assemblages from China (1) exhibited high mean tooth size and disparity early in the Paleocene, (2) shifted in their dental shape in parallel with regional and global environmental changes later in the Paleocene, and (3) achieved maximum dental shape-performance covariation near the end of the first 10 Myr post-K-Pg. This ‘brawn before bite’ transformation, coupled with prolonged dental shape versus performance variability, favors a scenario whereby many living orders of eutherian mammals were borne out of phenotypically and functionally plastic ancestral assemblages, including those in tropical South China, during the Paleocene.

Constraints on the G1/S transition pathway may favor selection of multicellularity as a passenger phenotype

bertrand.daignan-fornier@u-bordeaux.fr (Bertrand Daignan-Fornier) — Thu, 18 Jun 2026 00:00:00 +0000

Multicellularity has emerged in the three branches of the tree of life. The formation of simple multicellular entities can either result from cells aggregating or staying together after mitosis. However, it is not yet fully understood how, once formed, these simple multicellular entities could be maintained or even selected for. Here, using the ace2 yeast snowflake model of simple multicellularity, we aimed at identifying genetic conditions favoring its maintenance. Growth-competition experiments revealed that, while the ace2 mutation by itself does not provide any fitness advantage or disadvantage, the ace2 snowflakes were strongly selected when combined with conditions affecting regulators of the G1/S transition of the cell cycle, such as Cln3 or Whi5. We show that this selection results from a faster exit from quiescence of the ace2 snowflake cells. Importantly, this advantage is not dependent on the multicellular phenotype, but rather on the ace2 genotype itself. We found that the ace2 selective advantage in the cln3 background fully depends on the KSS1 gene, a target of the Ace2 transcription factor. Finally, we show that phenotypes observed for ace2 mutants are phenocopied by the AMN1^368D allelic form found in ‘non-laboratory’ yeast strains, hence adding physiological relevance to these observations. Altogether, our results support the hypothesis that simple multicellularity could, in some cases, persist, not because it provides a direct selective advantage due to multicellularity itself, but rather as a ‘passenger’ phenotype that is maintained alongside other selected traits.

Faroese whole genomes provide insight into ancestry and recent selection

fracimo@sund.ku.dk (Alba Refoyo-Martínez) — Tue, 16 Jun 2026 00:00:00 +0000

The Faroe Islands are home to descendants of a North Atlantic founder population with a unique history shaped by both migration and periods of relative isolation. Here, we investigate the genetic diversity, population structure, and demographic history of the islands by analyzing whole genome sequencing data from 40 participants in the Faroe Genome Project. This represents the first whole genome sequencing panel of this size from the Faroe Islands. We observed numerous putatively functional private alleles, including stop gain variants and high impact missense variants in the cohort. Faroese individuals had a higher proportion of their genomes contained in long runs of homozygosity than other European groups, including Finnish, suggesting a more recent or stronger bottleneck in the Faroese population. Signals of positive selection were identified at loci containing genes that play roles in vitamin D and dietary fat absorption and DNA repair, while increased diversity on lactase persistence haplotypes was observed. Fine-scale analysis of haplotype structure in present-day and ancient European genomes revealed genetic affinities with ancient Iron Age individuals from the North and West of Europe, providing evidence for potential contributions to the Faroese gene pool from Celtic and Viking populations as well as information about the temporal order in which these events happened. This study highlights the impact of evolutionary processes, such as ancient admixture, founder events, and positive selection, on the present-day genetic architecture of North Atlantic founder populations like the Faroe Islands.

Host and antibiotic jointly select for greater virulence in Staphylococcus aureus

tread@emory.edu (Jennifer D Gresham) — Tue, 16 Jun 2026 00:00:00 +0000

Widespread antibiotic usage has resulted in the rapid evolution of drug-resistant bacterial pathogens. Resolving how pathogens respond to antibiotics under different contexts is critical for understanding disease emergence. It remains unclear how interactions between hosts and antibiotics impact pathogen evolution. Here, we evolved Staphylococcus aureus, a major bacterial pathogen, varying exposure to host and antibiotics to tease apart the contributions of these selective pressures on pathogen adaptation. After 12 passages, S. aureus evolving in Caenorhabditis elegans nematodes exposed to a sub-minimum inhibitory antibiotic concentration became highly virulent, regardless of whether the ancestral pathogen was methicillin-resistant (MRSA) or methicillin-sensitive (MSSA). Host and antibiotic selected for reduced drug susceptibility in MSSA while increasing MRSA total growth outside hosts. We identified mutations in genes involved in regulatory networks linking virulence and metabolism, suggesting that rapid adaptation to infect hosts may have pleiotropic effects. Mutations that arose in these genes were also enriched in clinical isolates associated with systemic infections in humans. Despite evolving in similar environments, MRSA and MSSA populations—differing only in the presence of an intact accessory gene—proceeded on divergent evolutionary paths, with MSSA populations exhibiting more similarities across replicates. Our results underscore the importance of the host context as a driver of virulence and antibiotic resistance.

Are interphylum spiralian relationships resolvable?

m.telford@ucl.ac.uk (Ana Serra Silva) — Tue, 16 Jun 2026 00:00:00 +0000

The phyla making up the major animal clade of Spiralia have been clear since the advent of molecular phylogenetics; the relationships between these spiralian phyla have not. The lack of consensus over the relationships between these important animal phyla might be a clue implying their emergence in an explosive radiation. Focussing on the five largest spiralian clades (Annelida, Brachiozoa, Mollusca, Nemertea, and Platyhelminthes) and using two phylogenomic datasets, we have applied site-bootstrapping and taxon-jackknifing to explore this example of taxonomic instability. Analyses of the 105 possible rooted trees relating them showed that interphylum branches are very short. Preference for rooting Spiralia on Platyhelminthes is enhanced by a long-branch artefact. Most analyses on the 15 unrooted trees showed a preference for the same topology but the support for this tree over other solutions was not significant. We conclude that the spiralian phyla emerged in rapid succession resulting in a difficult-to-resolve radiation. The deep history we infer for Spiralia has wide-ranging implications for our interpretation of Cambrian fossils and for the evolution of traits such as biomineralisation, segmentation, and larvae.

Distinct evolutionary trajectories of two integration centres, the central complex and mushroom bodies, across Heliconiini butterflies

m.farnworth@bristol.ac.uk (Basil el Jundi) — Mon, 01 Jun 2026 00:00:00 +0000

Neural circuits evolved to produce variable cognitive processes through adaptive mechanisms operating within a background of developmental and functional constraints. Understanding how this conflict is resolved requires a comparative framework encapsulating clear behavioural variation. We leverage Heliconiini butterflies to examine how selection shaped the evolution of the central complex and mushroom bodies, two insect integration centres involved in navigation. The evolution of systematic spatial foraging in Heliconius has led to changes in brain morphology and learning and memory profiles over a short evolutionary timescale. Here, we show that in contrast to massively expanded mushroom bodies, the central complex is strongly conserved in size and general architecture. However, we identify divergences in the expression of a neuropeptide, Allatostatin A, in the noduli, and in the numbers of GABA-ergic ring neurons and their branching in the fan-shaped body, which are essential members of the anterior compass pathway. These differences are rare examples of divergence inside the central complex network matching expectations of where evolutionary adaptability might occur. We conclude that due to the contrasting volumetric conservation of the central complex, and the massive differences in the mushroom bodies, their circuit logics must determine distinct responses to selection associated with divergent foraging behaviours.

Rapid riparian ecosystem recovery in low-latitudinal North China following the end-Permian mass extinction

tianlibgeg@cug.edu.cn (Daoliang Chu) — Mon, 18 May 2026 00:00:00 +0000

The greatest mass extinction at the end of the Permian, ca. 252 million years ago, led to a tropical dead zone on land and sea. The speed of recovery of life has been debated, whether fast or slow, and terrestrial ecosystems are much less understood than marine. Here, we show fast reestablishment of riparian ecosystems in low-latitude North China as little as ~2 million years after the end-Permian mass extinction. The initial ichnoassemblages in shallow lacustrine and fluvial facies of late Smithian age are monospecific, devoid of infaunalization, with apparent size reduction. In the following Spathian, relatively complex, multi-level, structured riverain ecosystems had been rebuilt including medium-sized carnivores, plant stems, root traces, increased ichnological complexity, and significantly increased infaunalization. Specifically, burrowing behavior had re-emerged as a key life strategy not only to minimize stressful climatic conditions, but possibly to escape predation.

Recombination shapes the diversification of the wtf meiotic drivers

gongzhen@nnu.edu.cn (Guan-Zhu Han) — Mon, 11 May 2026 00:00:00 +0000

Meiotic drivers are selfish genetic elements that distort fair segregation. The wtf genes are poison-antidote meiotic drivers that are experiencing rapid diversification in fission yeasts. However, gene duplication alone is insufficient to drive the diversification of wtf genes, given the poison encoded by a newly duplicated wtf gene can be detoxified by the antidote encoded by the original wtf gene. Here, we analyze the evolution of wtf genes across 21 strains of Schizosaccharomyces pombe. Knocking out each of 25 wtf genes in S. pombe strain 972h- separately does not attenuate the yeast growth, indicating that the wtf genes might be largely neutral to their carriers in asexual life cycle. Interestingly, wtf genes underwent recurrent and intricate recombination. As proof of principle, we generate a novel meiotic driver through artificial recombination between wtf drivers, and its encoded poison cannot be detoxified by the antidotes encoded by their parental wtf genes but can be detoxified by its own antidote. Therefore, we propose that recombination can generate new meiotic drivers and thus shape the diversification of the wtf drivers.

Investments in photoreceptors compete with investments in optics to determine eye design

SL104@cam.ac.uk (Francisco JH Heras) — Tue, 05 May 2026 00:00:00 +0000

Eyes provide opportunities to understand the function, design, development, and evolution of elaborate sense organs. We take a new cost–benefit approach to understanding eye design by considering that optics and photoreceptors compete for the resources invested in an integrated system. We investigate this competition theoretically and empirically using a new measure of cost, specific volume. This common currency for optics and photoreceptors relates investments to image quality via geometrical, optical, and physiological constraints. By covering the morphospace of an eye of given type and cost, we model how trading optics against photoreceptors changes information capacity. In apposition compound eyes and simple eyes, an optimum configuration maximises efficiency. Efficiency requires heavy investment in photoreceptors and depends on photoreceptor energy consumption. Optimum information capacities and efficiencies scale non-linearly with total investment. Diurnal insects’ apposition eyes follow trends that promote efficiency: photoreceptor arrays take 40–80% of total specific volume, photoreceptor length increases systematically with spatial resolution, and photoreceptors are exceptionally long. Thus, competition between optics and photoreceptors shapes eye design, and matching investments in optics and photoreceptors to improve efficiency is a design principle. Our new methodology can be developed to view the adaptive radiation of eyes through a cost–benefit lens.

Inference of germinal center evolutionary dynamics via simulation-based deep learning

dralph@fredhutch.org (Ashni A Vora) — Tue, 28 Apr 2026 00:00:00 +0000

B cells and the antibodies they produce are vital to health and survival, motivating research on the details of the mutational and evolutionary processes in the germinal centers (GCs) from which mature B cells arise. It is known that B cells with higher affinity for their cognate antigen (Ag) will, on average, tend to have more offspring. However, the exact form of this relationship between affinity and fecundity, which we call the ‘affinity–fitness response function’, is not known. Here we use deep learning and simulation-based inference to learn this function from a unique experiment that replays a particular combination of GC conditions many times in mice. All code is freely available at https://github.com/matsengrp/gcdyn, while datasets and inference results can be found at https://doi.org/10.5281/zenodo.15022130.

Taking the biology seriously makes models better

a.gil@ucl.ac.uk (Andreas Tiffeau-Mayer) — Mon, 20 Apr 2026 00:00:00 +0000

A new biologically-informed training paradigm enables protein language models to predict affinity maturation trajectories for antibodies.

Adaptive variation in avian eggshell gas conductance and structure across elevational gradients?

docampo@princeton.edu (Carlos Daniel Cadena) — Tue, 14 Apr 2026 00:00:00 +0000

Many tropical bird species have restricted elevational distributions, potentially limited by how environmental conditions affect physiological processes. While some studies have examined adult physiology across elevations, relatively little attention has been given to the structure and function of eggshells despite their critical role in regulating gas exchange during the vulnerable embryonic stage. At high elevations, dry air is expected to increase water loss from the egg, and natural selection may favor lower gas conductance to reduce desiccation risk. Structural variation in eggshells, such as increased shell thickness or reduced pore size and density, could serve as a mechanism to regulate gas diffusion. To test for adaptive variation in eggshell traits along elevational gradients, we measured water vapor conductance and used scanning electron microscopy (SEM) to examine eggshell structure in 197 bird species from the Andes. We found that water vapor conductance declined at high elevations across avian communities. However, structural changes in eggshells varied among bird families and did not vary in a predictable way with elevation, suggesting no relationship or divergent adaptive responses to shared selective pressures, particularly in shell thickness, pore density, and pore size. We propose that examining functional and structural eggshell traits can offer insight into species’ elevational limits and inform predictions about their responses to climate change.

Fitness drivers of division of labor in vertebrates

igaru.13@gmail.com (Dustin R Rubenstein) — Wed, 08 Apr 2026 00:00:00 +0000

Although division of labor as a means to increase productivity is a common feature in animal social groups, most previous studies have focused almost exclusively on eusocial insects with extreme task partitioning. Empirical evidence of division of labor in vertebrates is scarce, largely because we lack a theoretical framework to explore the conditions under which division of labor is likely to evolve in cooperatively breeding systems where helpers remain capable of breeding throughout their lifetime. By explicitly considering alternative helping tasks with varying fitness costs, we model how individual decisions on task specialization may influence the emergence of division of labor under both direct and indirect fitness benefits. Surprisingly, we find that direct survival benefits of living in larger groups are the primary force driving the evolution of cooperation to enhance group productivity, and that indirect fitness benefits derived from related group members are only a non-essential facilitator of more stable forms of division of labor in cooperative breeders. In addition, we find that division of labor in vertebrates is favored by harsh environments. Ultimately, our model not only makes key predictions that are consistent with existing empirical data, but also proposes novel avenues for new empirical work in vertebrate and invertebrate systems alike.

Identification and comparison of orthologous cell types from primate embryoid bodies shows limits of marker gene transferability

enard@bio.lmu.de (Anita Térmeg) — Wed, 08 Apr 2026 00:00:00 +0000

The identification of cell types remains a major challenge. Even after a decade of single-cell RNA sequencing (scRNA-seq), reasonable cell type annotations almost always include manual non-automated steps. The identification of orthologous cell types across species complicates matters even more, but at the same time strengthens the confidence in the assignment. Here, we generate and analyze a dataset consisting of embryoid bodies (EBs) derived from induced pluripotent stem cells (iPSCs) of four primate species: humans, orangutans, cynomolgus, and rhesus macaques. This kind of data includes a continuum of developmental cell types, multiple batch effects (i.e. species and individuals) and uneven cell type compositions and hence poses many challenges. We developed a semi-automated computational pipeline combining classification and marker-based cluster annotation to identify orthologous cell types across primates. This approach enabled the investigation of cross-species conservation of gene expression. Consistent with previous studies, our data confirm that broadly expressed genes are more conserved than cell type-specific genes, raising the question of how conserved, inherently cell type-specific, marker genes are. Our analyses reveal that human marker genes are less effective in macaques and vice versa, highlighting the limited transferability of markers across species. Overall, our study advances the identification of orthologous cell types across species, provides a well-curated cell type reference for future in vitro studies and informs the transferability of marker genes across species.

Separating selection from mutation in antibody language models

matsen@fredhutch.org (David H Rich) — Tue, 07 Apr 2026 00:00:00 +0000

Antibodies are encoded by nucleotide sequences that are generated by V(D)J recombination and evolve according to mutation and selection processes. Existing antibody language models, however, focus exclusively on antibodies as strings of amino acids and are fitted using standard language modeling objectives such as masked or autoregressive prediction. In this paper, we first show that fitting models using this objective implicitly incorporates nucleotide-level mutation processes as part of the protein language model, which degrades performance when predicting effects of mutations on functional properties of antibodies. To address this limitation, we devise a new framework: a deep amino acid selection model (DASM) that learns the selection effects of amino acid mutations while explicitly factoring out the nucleotide-level mutation process. By fitting selection as a separate term from the mutation process, the DASM exclusively quantifies functional effects: effects that change some aspect of the function of the antibody. This factorization leads to substantially improved performance on standard functional benchmarks. Moreover, our model is an order of magnitude smaller and multiple orders of magnitude faster to evaluate than existing approaches, as well as being readily interpretable.

Human genetic ancestry, Mycobacterium tuberculosis diversity, and tuberculosis disease severity in Dar es Salaam, Tanzania

sebastien.gagneux@swisstph.ch (Amanda Ross) — Tue, 24 Mar 2026 00:00:00 +0000

Infectious diseases have affected humanity for millennia and are among the strongest selective forces. Tuberculosis (TB) is an ancient disease, caused by the human-adapted members of the Mycobacterium tuberculosis complex (MTBC). The outcome of TB infection and disease is highly variable, and co-evolution between human populations and MTBC strains may account for some of this variability. Particular human genetic ancestries have been associated with higher susceptibility to TB, but sociodemographic aspects of the disease can confound such associations. Here, we studied 1000 TB patients from Dar es Salaam, Tanzania, together with their respective MTBC isolates, by combining human and bacterial genomics with clinical data. We found that the genetic background of the TB patient population was strongly influenced by migrations of Bantu-speaking populations from West Africa, which contrasts with the corresponding MTBC genotypes that were mainly introduced from outside Africa. These findings suggest a recent evolutionary history of co-existence between the human and MTBC populations in Dar es Salaam. We detected no evidence of an effect of human genetic ancestry, or MTBC phylogenetic diversity alone, nor their interaction, on TB disease severity. There was also no evidence of an association between human variation genome-wide and TB disease severity. Treatment-seeking, social, and environmental factors are likely to be the main determinants of disease severity at the point of care in this patient population.

Developmental, regenerative, and behavioral dynamics in acoel reproduction

vchandra1@fas.harvard.edu (Allison P Kann) — Fri, 20 Mar 2026 00:00:00 +0000

Acoel worms are an enigmatic and understudied animal lineage. Sparse descriptions suggest a diversity of reproductive anatomies across acoels, and likely a corresponding behavioral diversity. Here, we study the reproductive life history of the acoel Hofstenia miamia, an emerging lab-tractable model system. We describe H. miamia’s reproductive organs, identifying structures previously unknown in acoels. Following worms from zygotes to adulthood, we find that their reproductive organs emerge in a stereotyped sequence as a function of increasing body size. These organs regenerate in a similar sequence after major injuries and are lost in the opposite sequence during starvation-induced de-growth, suggesting that organ growth may be regulated by a single, size-associated program in all contexts. Studying egg-laying behavior, we find that H. miamia lay their eggs through their mouths after loading them into their pharynges. Worms lay eggs for months after a single mating, suggesting long-term sperm storage despite lacking a storage organ. They can also lay viable eggs without mating, indicating a capacity for self-fertilization. Finally, worms assess past and present environmental features during egg-laying decisions, frequently laying eggs in communal clutches. Together, our work establishes foundational knowledge for the study of reproductive development, physiology, and behavior in acoels.

Earliest evidence of elephant butchery at Olduvai Gorge (Tanzania) reveals the evolutionary impact of early human megafaunal exploitation

mdr@rice.edu (Abel Moclan) — Wed, 18 Mar 2026 00:00:00 +0000

The role of megafaunal exploitation in early human evolution remains debated. Occasional use of large carcasses by early hominins has been considered by some as opportunistic, possibly a fallback dietary strategy, and for others a more important survival strategy. At Olduvai Gorge, evidence for megafaunal butchery is scarce in the Oldowan of Bed I but becomes more frequent and widespread after 1.8 Ma in Bed II, coinciding with the emergence of Acheulean technologies, but not functionally related to the main Acheulian tool types. Here, we present the earliest direct evidence of proboscidean butchery, including a newly documented elephant butchery site (EAK). This shift in behavior is accompanied by larger, more complex occupation sites, signaling a profound ecological and technological transformation. Rather than opportunistic scavenging, these findings suggest a strategic adaptation to megafaunal resources, with implications for early human subsistence and social organization. The ability to systematically exploit large prey represents a unique evolutionary trajectory, with no direct modern analogue, since modern foragers do so only episodically.

Toward neuroanatomical and cognitive foundations of macaque social tolerance grades

sebastien.ballesta@gmail.com (Chrystelle Po) — Tue, 03 Mar 2026 00:00:00 +0000

The macaque genus includes 25 species with diverse social systems, ranging from low to high social tolerance grades. Such interspecific behavioral variability provides a unique model to tackle the evolutionary foundation of primate social brain. Yet, the neuroanatomical correlates of these social tolerance grades remain unknown. To address this question, we expressed social tolerance grades within a novel cognitive framework and analyzed post-mortem structural scans from 12 macaque species. Our results show that amygdala volume is a subcortical predictor of macaques’ social tolerance, with high tolerance species exhibiting larger amygdala than low tolerance ones. We further investigated the developmental trajectory of amygdala across social grades and found that intolerant species showed a gradual increase in relative amygdala volume across the lifespan. Unexpectedly, tolerant species exhibited a decrease in relative amygdala volume across the lifespan, contrasting with the age-related increase observed in intolerant species—a developmental pattern previously undescribed in primates. Taken together, these findings provide valuable insights into the cognitive, neuroanatomical, and evolutionary basis of primates’ social behaviors.

High-throughput neutralization measurements correlate strongly with evolutionary success of human influenza strains

jbloom@fredhutch.org (Andrea N Loes) — Mon, 23 Feb 2026 00:00:00 +0000

Human influenza viruses rapidly acquire mutations in their hemagglutinin (HA) protein that erode neutralization by antibodies from prior exposures. Here, we use a sequencing-based assay to measure neutralization titers for 78 recent H3N2 HA strains against a large set of children and adult sera, measuring ~10,000 total titers. There is substantial person-to-person heterogeneity in the titers against different viral strains, both within and across age cohorts. The growth rates of H3N2 strains in the human population in 2023 are highly correlated with the fraction of sera with low titers against each strain. Notably, strain growth rates are less correlated with neutralization titers against pools of human sera, demonstrating the importance of population heterogeneity in shaping viral evolution. Overall, these results suggest that high-throughput neutralization measurements of human sera against many different viral strains can help explain the evolution of human influenza.

On the nature of the earliest known lifeforms

dheerajbio@gmail.com (Andreas Klingl) — Tue, 17 Feb 2026 00:00:00 +0000

Microfossils from the Paleoarchean Eon are the oldest known evidence of life. Despite their significance in understanding the history of life on Earth, any interpretation of the nature of these microfossils has been a point of contention among researchers. Decades of back-and-forth arguments led to the consensus that reconstructing the lifecycles of Archaean Eon organisms is the most promising way of understanding the nature of these microfossils. Here, we transformed a Gram-positive bacterium into a primitive lipid vesicle-like state and studied it under environmental conditions prevalent on early Earth. Using this approach, we successfully reconstructed morphologies and life cycles of Archaean microfossils. In addition to reproducing microfossil morphologies, we conducted experiments that spanned years to understand the process of cell degradation and how Archaean cells could have undergone encrustation of minerals (in this case, salt), leading to their preservation as fossilized organic carbon in the rock record. These degradation products strongly resemble fossiliferous features from Archaean rock formations. Our observations suggest that microfossils aged between 3.8–2.5 Ga most likely were liposome-like protocells that have evolved physiological pathways of energy conservation but not the mechanisms to regulate their morphology. Based on these observations, we propose that morphology is not a reliable indicator of taxonomy in these microfossils.

Kinematics and morphological correlates of descent strategies in arboreal mammals suggest early upright postures in euprimates

severine.toussaint@mnhn.fr (Dionisios Youlatos) — Tue, 17 Feb 2026 00:00:00 +0000

Ascending and descending sloping and vertical branches are critical for arboreal locomotion and likely played a major role in early primate evolution. While most studies have focused on ascent, descending behaviors also provide insight into the functional significance of arboreal adaptations. To test how descending vertical supports of varying diameters affect locomotor abilities, we quantified postural and kinematic features during descents and ascents on vertical supports in 21 eutherian and metatherian mammals and examined their relation to morphology. Primates showed greater variability in descent behaviors, using tail-first and side postures more often than other mammals, which predominantly descended head-first. Overall, animals adopted several kinematic adjustments to enhance stability during descent compared to ascent, including slower speeds, higher duty factors, and greater use of asymmetrical gaits. Additionally, vertical descent strategies reflected trade-offs among body mass, limb proportions, and head mass. Using a morphology-based model, we then inferred possible descent behaviors in 13 extinct euarchontoglires. Our results suggest that ancestral adaptations for vertical locomotion may have promoted frequent upright (head-up) postures in early primates.

Accelerated evolution in networked metapopulations of Pseudomonas aeruginosa

rees.kassen@mcgill.ca (Partha Pratim Chakraborty) — Thu, 29 Jan 2026 00:00:00 +0000

Natural populations are often spatially structured, meaning they exist as metapopulations composed of subpopulations connected by migration. Little is known about the impact of spatial structure, in particular the topology of connections among subpopulations, on adaptive evolution. Typically, spatial structure slows adaptation, although some models suggest topologies that concentrate dispersing individuals through a central hub can accelerate adaptation above that of a well-mixed system. We provide evidence to support this claim and show acceleration is accompanied by high rates of parallel evolution. Our results suggest metapopulation topology can be a potent force driving evolutionary dynamics and patterns of genomic repeatability in structured landscapes such as those involving the spread of pathogens or invasive species.

Hybridization breaks species barriers in long-term coevolution of a cyanobacterial population

gbirzu@ufl.edu (Danielle Goudeau) — Wed, 31 Dec 2025 00:00:00 +0000

Bacterial species often undergo rampant recombination yet maintain cohesive genomic identity. Ecological differences can generate recombination barriers between species and sustain genomic clusters in the short term. But can these forces prevent genomic mixing during long-term coevolution? Cyanobacteria in Yellowstone hot springs comprise several diverse species that have coevolved for hundreds of thousands of years, providing a rare natural experiment. By analyzing more than 300 single-cell genomes, we show that despite each species forming a distinct genomic cluster, much of the diversity within species is the result of hybridization driven by selection, which has mixed their ancestral genotypes. This widespread mixing is contrary to the prevailing view that ecological barriers can maintain cohesive bacterial species and highlights the importance of hybridization as a source of genomic diversity.