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The assumption that a complex and fuzzy notion like smile can be the basis of a scientific, rather than semantic, inquiry can only lead to confused and inconclusive results. It would be more productive to start with the well-defined and measurable patterns of the clearly: visible contrasts that are produced on the human face by various muscular contractions around the white patches formed by the sclera and the teeth. These features are universal, whereas a common word, in whatever language, is necessarily ambiguous, culture-dependent, and historically rather than biologically determined. doi: 10.1017/S0140525X10001627

This commentary questions the general assumptions concerning the cognitive value of analogical reasoning on which the argument developed by Leech et al. appears to rest. In order to better assess the findings of their meta-analysis, it shifts the perspective from development to evolution, and frames their 'how' concern within a broader 'why' issue.

The target article authors have been drawn into two metaphoric models of attitudes toward money that have prevented them from developing a convincing evolutionary theory able to account for the various behaviors they list and categorize as either tool-type or drug-type. Instead, hoarding could provide an evolutionary model that is better supported by behavioral and neurological evidence and could account for the whole range of behaviors they review. Moreover, the authors' focus on money as the common denominator of these behaviors brings an ideological bias to their inquiry.

Falk's hypothesis is attractive and seems to be supported by data from primatology and language acquisition literature. However, this etiological narrative presents a fairly low degree of plausibility, the result of two epistemological fallacies: an implicit reliance on a unilinear model of causality and the explicit belief that ontogeny is homologous to phylogeny. Although this attempt to retrace the early emergence of prelinguistic capacities in hominins falls short of producing a compelling argument, it does call attention to an aspect of linguistic behavior which may indeed have evolved under the pressure of nurturing constraints.