Title of Dataset Associated Supplementary Material associated with Grabowski et al. (2023) - Both Diet and Sociality Affect Primate Brain-Size Evolution Description of the data and file structure 1. Grabowski_SB Data File S1.xlsx - Data includes Microsoft Excel file with complete data (Data File S1) associated with Grabowski et al. (2023). This is broken down into primate species information for brain and body size with calculated measurement error, summary diet data, diet data from multiple sources, sociality data, and group size and activity data, separated by tabs in the Excel file. Color coding is explained on each sheet but relates to whether or not a datum was used in the analysis and/or is new to this dataset. All abbreviations are explained on the associated Excel sheets. 2. Grabowski_SB_10K.tre - modified phylogeny based on 10K Trees Primate Phylogeny with species attributions updated to match dataset. 3. Grabowski_SB Data File References - Complete references for the data file. 4. Grabowski_et_al._2023_Supplementary_Text - Additional results and discussion associated with Grabowski et al. (2023). 5. Grabowski_et_al._2023_Supplementary_Tables.xlsx - Supplementary results in Microsoft Excel file associated with Grabowski et al. (2023). Dataset citation: Grabowski M., Kopperud B.T., Tsuboi M., Hansen T.F. 2023. Both Diet and Sociality Affect Primate Brain-Size Evolution. Systematic Biology.:syac075.

Increased brain size in humans and other primates is hypothesized to confer cognitive benefits but brings costs associated with growing and maintaining energetically expensive neural tissue. Previous studies have argued that changes in either diet or levels of sociality led to shifts in brain size, but results were equivocal. Here we test these hypotheses using phylogenetic comparative methods designed to jointly account for and estimate the effects of adaptation and phylogeny. Using the largest current sample of primate brain and body sizes with observation error, complemented by newly compiled diet and sociality data, we show that both diet and sociality have influenced the evolution of brain size. Shifting from simple to more complex levels of sociality resulted in relatively larger brains, while shifting to a more folivorous diet led to relatively smaller brains. While our results support the role of sociality, they modify a range of ecological hypotheses centered on the importance of frugivory and instead indicate that digestive costs associated with increased folivory may have resulted in relatively smaller brains.

Data on brain and body size, sociality, and diet were collected from the literature, and species-level measurement error in brain and body size was calculated following Grabowski et al. (2016). Supplementary text includes additional results not included in main article.

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