Fig 1.
Drivers often proposed to explain the unique pattern of human handedness direction.
Humans show an unparalleled level of rightwards handedness bias as compared to other anthropoid clades.
Fig 2.
Traits analyzed in the present study and maximum credibility clade tree for the analyzed anthropoid species.
The acronyms correspond to: MHI, mean handedness index; MABSHI, mean absolute handedness index; BM, body mass [kg]; ECV, endocranial volume [cm3]; FRUIT, percentage of fruits in diet; DIET, percentage of fruits and animals in diet; IMI, intermembral index; DIM, body mass sexual dimorphism; TOOL, tool use [0 = absence, 1 = presence); SUBS, substrate preference [0 = arboreal, 1=both, 2 = terrestrial]; SOC-SYS, social system [0 = solitary, 1 = pair, 2 = group]; CL, intra-sexual competition levels sensu [1–4,70]; EXT, extractive foraging [0 = absence, 1 = presence]; social learning sensu [71] [0 = absence, 1 = presence]. Traits are color coded from lower to higher values. In the case of the discrete traits, colors also go from lower to higher values based on the categorization provided in this legend. Cercopithecoidea, Hominoidea and Platyrrhini are represented by different silhouettes, as well as colors. The data underlying this Figure can be found in S2 Data.
Fig 3.
Coefficient estimate distributions for the reduced models and phylogenetic outlier tests for MHI and MABSH.
The upper for panels show the coefficient estimate distributions for the reduced models: (a) MHI excluding Homo sapiens, (b) MHI including H. sapiens, (f) MABSHI excluding H. sapiens, and (g) MABSHI including H. sapiens. Effects are considered credible when the 95% credibility intervals (light shaded areas) do not overlap with zero (dotted line). The median for each coefficient distribution is represented by darker solid lines. Credible predictors are marked with asterisks. The lower four panels present the posterior distribution of predictions for MHI and MABSHI for a new Homo sapiens observation. It illustrates these predictions based on the reduced models: (c) MHI excluding humans, (d) MHI including humans, (h) MABSHI excluding humans, and (i) MABSHI including humans. All predictions are marginalized over meta-analytical and non-phylogenetic species random effects. The data underlying this Figure can be found in S2 Data.
Fig 4.
Predicted handedness in hominin species based on the reduced models including Homo sapiens.
Right-hand colors represent the predicted magnitude of MHI; left-hand colors show the corresponding negative values (i.e., greater color differences between hands reflect stronger handedness direction bias). Hand size is proportional to handedness strength, MABSHI. The phylogeny is the maximum a posteriori tree from ref [34]. Only hominin species with complete relevant covariate data were included in the analysis and are shown here. The handedness values for Pan troglodytes and Homo sapiens correspond to observed data. The data underlying this Figure can be found in S2 Data.