Making Friends , Making Tools , and Making Symbols by Matt

art. This transition may, in fact, be a requisite one for symbolism to provide any substantive fitness advantage. Until the brain is capable of supporting a level of symbolic complexity such that social life itself can be symbolically organized, then symbolism may be of only marginal consequence. What, then, were the selective factors behind this watershed transition? Social Complexity and Cognitive Evolution That social pressure might be critical in human brain and cognitive evolution is becoming an increasingly prominent theme (Alexander 1989; Dunbar 2007; Geary 2005; Powell, Shennen, and Thomas 2009). Those of our ancestors who were best able to track social relationships, build strategic alliances, and make vital judgments about intentions and trustworthiness very likely gained a fitness advantage. Furthermore, a long tradition of psychological research has established the inferentially and computationally demanding nature of social cognition (Gilbert, Pelham, and Krull 1988; Heider 1958; Trope 1986). These demands are especially acute in executive functions such as attention, working memory, and cognitive control. One recent study has provided both correlational and experimental data supporting the notion that social engagement itself activates working memory and improves cognitive functioning (Ybarra et al. 2008). Thus, as the H. sapiens social world expanded and complexified, executive functions including working memory came under in-