Data from: Pattern and process in hominin brain size evolution are scale-dependent

A large brain is a defining feature of modern humans, yet there is no consensus regarding the patterns, rates, and processes involved in hominin brain size evolution. We use a reliable proxy for brain size in fossils, endocranial volume (ECV), to better understand how brain size evolved at both clade- and lineage-level scales. For the hominin clade overall, the dominant signal is consistent with a gradual increase in brain size. This gradual trend appears to have been generated primarily by processes operating within hypothesized lineages – 64% or 88% depending on whether one uses a more or less speciose taxonomy, respectively. These processes were supplemented by the appearance in the fossil record of larger-brained Homo species and the subsequent disappearance of smaller-brained Australopithecus and Paranthropus taxa. When the estimated rate of within-lineage ECV increase is compared to an exponential model that operationalizes generation-scale evolutionary processes, it suggests that the observed data were the result of episodes of directional selection interspersed with periods of stasis and/or drift; all of this occurs on too fine a time scale to be resolved by the current human fossil record, thus producing apparent gradual trends within lineages. Our findings provide a quantitative basis for developing and testing scale-explicit hypotheses about the factors that led brain size to increase during hominin evolution.Appendix S1Supplementary methods, results, figures, and tables for the analysis.Du et al 2018 revised Appendix S1 R2_ESM_FINAL changes accepted.docxTable S1Excel spreadsheet with the raw data used for all analyses. Each row is a separate specimen along with its ID. Columns include the "lumper's" and "splitter's" taxonomy used in the random effects ANOVA to get inter-observer error ("lump.taxon" and "split.taxon"), the less and more speciose lineages used in the lower-taxonomic additive partitioning analyses ("lump.part" and "split.part"), region where each specimen comes from which aided in the allocation of specimens to lineages ("region"), grade for coding points in fig. 2 ("grade"), which specimens were excluded for the damaged specimens sensitivity analysis ("reliab.sens"), ECV replicate measurements from different researchers ("ecv1" to "ecv6"), and the various dates for each specimen ("min.date", "max.date", "mean.date", and "sd.date") and their respective age error distribution ("date.dist").ProcB SI ECV dataset FINAL.xlsxR scriptR script for (1) running variance partitioning analyses to get inter-observer endocranial volume (ECV) error, (2) fitting evolutionary mode models to the hominin clade-level ECV data using the R package "paleoTS", (3) calculating R2 and model parameters for the gradualism model, and (4) running the lower taxonomic level additive partitioning analyses.Du et al R script_ESM.txtFunding provided by: National Science FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/100000001Award Number: DGE-08016