Martin, J. S. | bioRxiv Science

bioRxiv2025

Pair-Living Emerged Early in Placental Mammals

It is widely assumed that the first placental mammals were solitary. This assumption has been used as the default in previous comparative studies, but has never been tested independently. Here, we compiled a comprehensive database by reviewing over 14,000 primary peer-reviewed publications on the social organization of the 5,386 extant placental mammal species. We found empirical data for 738 species across 1,478 populations: 354 populations were primarily solitary, 241 populations pair-living and 878 populations group-living. Notably, 383 species (52%) and 580 populations (39%) exhibited intra-specific variation in social organization. Using a Bayesian phylogenetic framework that incorporates intra-specific variation, we show that the ancestral placental mammal - living approximately 160 to 100 million years ago - was not exclusively solitary, but likely displayed intraspecific variation. Pair-living was predicted to account for approximately 26% of ancestral social organisation. Our analysis found that ecology and life history of extant solitary and pair-living mammals was very similar and different from those of group-living mammals. Our results revise prevailing theories of mammalian social evolution, revealing that pair-living emerged early, shifting the focus of mammalian social evolution from the origins of pair-living to the origins of group-living.

evolutionary biology↗

bioRxiv2022

Primate Social Organization Evolved from a Flexible Pair-Living Ancestor

Explaining the evolution of primate social organization has been fundamental to understand human sociality and social evolution more broadly. It has often been suggested that the ancestor of all primates was solitary and that other forms of social organization evolved later. However, previous research included the assumption that many understudied primate species were solitary, then finding transitions to more complex social systems being driven by various life history traits and ecological factors. Here we show that when intra-specific variation is accounted for, the ancestral social organization of primates was variable, with the most common social organization being pair-living but with approximatively 15-20% of social units of the ancestral population deviating from this pattern by being solitary living. We built a detailed database from primary field studies quantifying the number of individuals (social units) expressing different social organizations in each population. We used Bayesian phylogenetic models to infer the probability of each social organization, conditional on several socio-ecological predictors, in ancestral populations. Body size and activity patterns had large effects on transitions between types of social organizations. Our results challenge the assumption that ancestral primates were solitary and that pair-living evolved afterwards. Moreover, our results emphasize the importance of focusing on field data and accounting for intra-specific variation. Pair-living is evolutionary ancient, likely caused by reproductive benefits such as access to partners and reduced intra-sexual competition, with more complex social structure (pair-bonding) and care systems (biparental and allo-parental care) evolving later. Significance StatementWas the ancestor of all primates a solitary-living species? Did more social forms of primate societies evolve from this basic and simple society? The dogma has been that the answer is yes. We used a modern statistical analysis, including variations within species, to show that the ancestral primate social organization was most likely variable. Most lived in pairs, and only 15-20% of individuals were solitary. Living in pairs was likely ancient and caused by reproductive benefits, like access to partners and reduced competition with the sexes. More complex social elaborations like pair-bonds, and biparental and allo-parental care, probably evolved later.

evolutionary biology↗

bioRxiv2017

HUGIn: Hi-C Unifying Genomic Interrogator

MotivationHigh throughput chromatin conformation capture (3C) technologies, such as Hi-C and ChlA-PET, have the potential to elucidate the functional roles of non-coding variants. However, most of published genome-wide unbiased chromatin organization studies have used cultured cell lines, limiting their generalizability.\n\nResultsWe developed a web browser, HUGIn, to visualize Hi-C data generated from 21 human primary tissues and cell liens. HUGIn enables assessment of chromatin contacts both constitutive across and specific to tissue(s) and/or cell line(s) at any genomic loci, including GWAS SNPs, eQTLs and cis-regulatory elements, facilitating the understanding of both GWAS and eQTLs results and functional genomics data.\n\nAvailabilityHUGIn is available at http://yunliweb.its.unc.edu/HUGIn.\n\nContactyunli@med.unc.edu and hum@ccf.org\n\nSupplementary information:

genetics↗