Figure 2.

Inferred Pathways of Tool Use Emergence across Taxa

(A) Posterior orderings of mode acquisition. The radius of a disk is proportional to the posterior probability that a given mode (horizontal axis) is acquired at a given step (vertical axis) in a pathway starting with no acquired modes. Blue disks give posteriors from inference given the phylogenetic relationship in Figure 1; red circles give (similar) posteriors from inference assuming convergent acquisitions (independent taxa). Numbers correspond to “classes” in the text, distinguished by higher probabilities of early (1) to late (4) acquisition; asterisks denote notably bimodal distributions.

(B) High-probability subset of pathways through the hypercubic space of tool mode acquisitions. Each node is a state corresponding to a specific pattern of mode presence or absences. State a is the state of no modes; state b is the state of all modes acquired (thus including chimpanzees, orangutans, NW monkeys). Nodes corresponding to different observed taxa are highlighted; nodes are colored red-violet according to number of acquired modes. Edge width is proportional to the posterior probability of the corresponding transition between states. Two pathway groups closely following state a can be observed, which further branch into pathways occupying the core and periphery of the plot. NW, New World; OW, Old World.