Van Lange et al. present the CLASH model wherein average temperature and seasonal fluctuation influence self-control and future orientation, which in turn explains aggression and violence as they vary within and between countries. The authors contrast their CLASH model, derived from evolutionary-ecological theories, such as Life History (LH) Theory, with proximate models that focus on immediate environmental effects. We agree with the authors on the need to progress toward an ultimate explanation, derived from climate and LH variation. Nevertheless, we believe that the distinction made by the authors between ultimate and proximate explanations (Scott-Phillips et al. Reference Scott-Phillips, Dickins and West2011) can be more precise. Our commentary thus focuses on disaggregating the two by asking for more clarification through the following questions: (1) How do self-control and future orientation relate to LH Theory? (2) Does biogeographical variation in climate and seasonality influence self-control and future orientation facultatively, developmentally, or evolutionarily? (3) How does the CLASH model's explanation of biogeographical variation relate to previous literature that clearly links biogeographical variation to evolved racial variation?

Proximate/ultimate distinctions come from specifying whether future orientation and self-control are subordinate expressions of LH or independently evolved and predictive variables. Pursuant to this, some approach measurement using single measures of biological or psychological traits relative to a constrained definition of LH strategy (Copping et al. Reference Copping, Campbell and Muncer2014), whereas others approach measurement using integrated complexes of behavioral, cognitive, and psychosocial traits relative to a broad definition of LH strategy (Figueredo et al. Reference Figueredo, Cabeza de Baca, Black, García, Fernandes, Wolf and Woodley of Menie2015a; Reference Figueredo, Patch, Ceballos, Zeigler-Hill, Welling and Shackelford2015b). Although life history is in any case a suite of strategically related traits (Stearns Reference Stearns1992), the broad conceptualization of Life History Theory clearly encompasses both future orientation and self-control (Figueredo et al. Reference Figueredo, Cabeza de Baca, Black, García, Fernandes, Wolf and Woodley of Menie2015a; Reference Figueredo, Patch, Ceballos, Zeigler-Hill, Welling and Shackelford2015b). The LH variables of encephalization, intelligence, and most specifically executive control relate centrally to both future orientation and self-control, as pace of life, anxiety, and risk assumption do so peripherally. On this basis, we ask Van Lange et al. to define their approach to LH Theory, specifically commenting on whether self-control and future orientation are understood to be conceptually and empirically distinct as explicitly illustrated in their Figure 1, or simply emphasized because they are exceptionally important LH predictors of aggression and violence. As subscribers of the broad psychometric approach (Figueredo et al. Reference Figueredo, Vásquez, Brumbach, Sefcek, Kirsner and Jacobs2005), we find it arbitrarily isolating and possibly erroneous to separate future orientation and self-control because suites of psychological traits, not just these two constructs, should be under the same ecological and climatologic selective pressures (Hertler Reference Hertler2015; Reference Hertler2016). To the extent that self-control and future orientation are understood as LH variables responsive to varying ratios of intrinsic and extrinsic mortality, proximate/ultimate relationships measured by the CLASH model become clearer, but with the effect of undermining the novelty of its contribution.

Clarifying the CLASH model's assumptions concerning proximate/ultimate causation also entails specifying the degree to which climatic effects on aggression and violence are evolutionary, developmental, or facultative. In other words, do average temperature and seasonality influence the decisions of adults, alter the development of children, or shape the evolution of populations? Terminology (adopt, enact, make), phrases (“willingness to engage in behaviors reflective of a slow life strategy”), citations of seasonal changes, and indiscriminate references to homogeneous old-world countries and heterogeneous new-world countries suggest Van Lange et al. favor facultative responses to climate, even when directly speaking of life history. In the most explicit statement to the contrary, Van Lange et al. state that “traits such as fast life [history] strategy, time orientation, and self-control evolved or developed” (sect. 5.1, para. 3). Though there is research indicative of facultative change (Dunkel et al. Reference Dunkel, Mathes and Beaver2013), developmental (Mittal et al. Reference Mittal, Griskevicius, Simpson, Sung and Young2015) and evolutionary (Rushton Reference Rushton1985a) explanations of LH strategy predominate, and can be applied dynamically when explaining biogeographical LH variation: Developmental models of LH Theory have discussed the salience of parent-child relationships and household dynamics in the development of reproductive and social strategies. Over developmental time, the family and household dynamics should either be a reflection of or a buffer against the outside environment (Belsky et al. Reference Belsky, Steinberg and Draper1991). This means individual variation should exist for these traits. However, if the same conditions persist and affect the household dynamics similarly, over phylogenetic time we should expect to see a convergence of traits across ancestors and subsequent generations, as is in fact the case judging from high heritability of life history (Figueredo & Rushton Reference Figueredo and Rushton2009), future orientation (Anokhin et al. Reference Anokhin, Grant, Mulligan and Heath2015), self-control (Niv et al. Reference Niv, Tuvblad, Raine, Wang and Baker2012), and also aggression and violence (Kendler et al. Reference Kendler, Maes, Lönn, Morris, Lichtenstein, Sundquist and Sundquist2015; Rushton et al. Reference Rushton, Fulker, Neale, Nias and Eysenck1986).

CLASH would be refined by referencing additional biogeographical theories that make explicit proximate/ultimate causal inferences. Moynihan (Reference Moynihan1993) found a correlation of r = 0.52 between U.S. state capitals' proximity to the Canadian border and eighth grade math scores, which led to his sardonic policy proposal of moving states closer to the Canadian border. As it stands, CLASH would result in similar proposals for violence reduction. In contrast, “cold winter theories” have posited that ancestral environments produced distinct evolutionary pressures, affecting behavioral and cognitive traits (Lynn Reference Lynn1991). Planning, future orientation, reduced aggression and violence, conscientiousness, general intelligence, and related slow LH traits are clearly described as evolved responses, requisite for survival and reproduction in northerly latitudes (Lynn Reference Lynn1991; Rushton Reference Rushton1985a; Hertler Reference Hertler2015; see Woodley Reference Woodley2011 on why intelligence may not directly correlate with LH strategy).

CLASH benefited from the inclusion of LH Theory, but minimized its importance. Not only are future orientation and self-control LH variables, but so are the aggression and violence they purportedly explain. From thence stemmed confusion of ultimate and proximate. With this reorientation, we clarify our position: Climatic variation ultimately causes evolved biogeographical LH variation, which proximally explains a complex of biological and behavioral LH traits, among which are future orientation, self-control, violence, and aggression. Van Lange et al.'s CLASH model, with its important emphasis on biogeography, its careful review of literature, and its insightful emphasis on seasonality, is nonetheless an important spur, which may renew the biogeographical study of LH and all its component parts.