Uncorrected proofs -  John Benjamins Publishing Company chapter 9 he heterochronic origins of explicit reference David A. Leavens, William D. Hopkins and Kim A. Bard Explicit reference is the communicative capacity to intentionally pick out a speciic object in the environment and make that object a manifest topic for shared attention. Pointing is the quintessential example of non-verbal, explicit reference. Chimpanzees, and other apes in captivity, spontaneously point without overt training. Because wild apes almost never point, and because both captive and wild apes are sampled from the same gene pool, this implies that, for apes, hominoid genes interact with certain environments to elicit pointing. We propose that changes in the patterns of hominid development interact with ape-like cognitive capacities to produce features of explicit reference in human infants, a capacity that emerges in our nearest living relatives when they experi- ence similar circumstances. 1. Introduction Despite a number of claims to the contrary (e.g., Butterworth and Grover 1988; Petitto 1988; Povinelli, Bering and Giambrone 2003a) pointing is frequently dis- played by captive apes (e.g., Leavens 2004; Leavens and Hopkins 1998, 1999). Captive apes usually point in apparent requests for delivery of food, but they will also point out the location of tools required to gain access to food (Call and Tomasello 1994; Russell, Braccini, Buehler, Kachin, Schapiro and Hopkins 2005; Whiten 2000). One chimpanzee, Clint, oten pointed to experimenters’ shoes, which he subsequently manipulated with apparent satisfaction, upon presentation of said shoes (Leavens, Hopkins and Bard 1996). Pointing is, manifestly, a referential act, directing the at- tention, the movements or the actions of an observer to a speciic locus. It has been argued that nonhumans both do not and cannot point because the psychological basis for their pointing-like behaviour difers from that of hu- mans who point (e.g. Povinelli et al. 2003a; Tomasello 2006). We believe that the psychological aspects of pointing and other communicative acts are distributed between signaler and receiver, and that the psychological basis of pointing cannot be correctly attributed to an individual, but to that individual, and any and all