The force of selection on survival changes with age and models of reproductive effort (RE) reflect this finding that increases in infant and adult mortality have different effects on optimal effort. Using an age-structured demographic model, I show that infant mortality constrains selection on the human life cycle. Effort directed at increasing infant survival is strongly favored over efforts to increase adult survival. Complete accounts of human reproductive decisions require age-specificity of effects.

The two-tiered model of developmental plasticity is elegant and presented with impressive interdisciplinary synthesis. We suggest that yet more – social context and nutrition behavior – will need to be incorporated into empirical research. Drawing from anthropology, nutrition, and neuroscience, we highlight connections that may help generate new approaches for studying the developmental calibration of life history in humans.

ER&K recurrently emphasize one side of three equations: (1) extrinsic rather than intrinsic mortality pressures; (2) developmental rather than genetic influence; and (3) individual rather than population-level effects. Furthermore, they insufficiently disambiguate extrinsic from intrinsic mortality, especially confounding how mortality evolutionarily constrains and developmentally calibrates genotypic life history speed, and struggle to explain population-level differences in fast maturation among modern populations.

The number and timing of births are strongly associated with the stability of available resources and the risk of extrinsic mortality. The authors suggest a verbal model to disentangle the relationship between these two variables. However, we challenge their assumption of a hierarchical relationship between these two predictors and propose that formal modelling of their interaction, within a developmental perspective, could further our understanding of how the reproductive strategies of women respond to environmental uncertainty.

Environmental factors do not directly drive life history outcomes. Rather, their influence is mediated by cognitive and affective processes. Here we review several psychological processes, which mediate the influence of environmental mortality on life history strategies in both Tier 1 and 2 from the target article.

Hierarchical response models are advancing our understanding of the facultative adjustment of development and reproduction to the environment. E, R, and K’s manuscript brings together a vast array of empirical data to support their Tier 2 model highlighting the importance of both the energetic and local mortality environments for reproductive development and timing. We propose that incorporating existing hierarchical response models, as well as analyses from industrial societies, will aid the hunt for underlying mechanisms that embody the local mortality environment impacting reproductive schedules.

Harsh extreme-Earth and extra-Earth mortality sources pressure countervailing shifts in human life-history traits and survival-reproductive strategies, trading shorter lifespans and reproduction spans to hedge scarce gametes with sex-chromosome resilience. Darwinian trajectories for genotypes and phenotypes nonetheless remain unknown for future Earth-population sustainability and deep-space colonization. Controversial technology-assisted human evolution may be needed to narrow anthropological evolutionary-medicine disparities and prevent Humanity’s extinction.

This commentary expands Ellis et al.’s 2-tiered life history (LH) model by integrating shyness and insecure attachment as mediators of environmental adaptation. Shyness balances survival-reproduction trade-offs with mixed LH outcomes. Avoidant attachment accelerates LH strategies under harsh conditions; anxious attachment delays reproduction under unpredictable conditions. Incorporating social behaviors, which are related to survival and safety, enhances the model’s applicability across behavioral domains.

The two-tiered model offers a meaningful advance in life history theory, but refinements are needed to enhance testability. We highlight challenges related to the timing of Tier 1 and 2 effects and potential curvilinearity in Tier 2 responses. Clarifying these dimensions would improve falsifiability and strengthen the model’s utility for guiding empirical research.

While Ellis, Reid, and Kramer’s life history framework is convincing in explaining individual variation in life history strategies, it has certain limitations, which we discuss – drawing notably on the economic theory of fertility choice. In particular, we suggest that ambient cues to extrinsic mortality alone are not sufficient to trigger sustained net fertility decline.

Life-history theory is a valuable framework to derive predictions about species-level and population-level adaptations, but it says little about variation between the individuals within a population. Conflating these different aggregate levels constitutes a mereological fallacy and may yield wrong conclusions. I argue that formal models are necessary to disentangle the mechanisms underlying individual-level and population-level variation in life-history traits.

Guided by concepts from life history (LH) theory, a large human research literature has tested the hypothesis that exposures to extrinsic mortality (EM) promote the development of faster LH strategies (e.g., earlier/faster reproduction, higher offspring number). A competing model proposes that, because EM in the past was intimately linked to energetic constraints, such exposures specifically led to the development of slower LH strategies. We empirically address this debate by examining (1) LH variation among small-scale societies under different environmental conditions; (2) country-, regional-, and community-level correlations between ecological conditions, mortality, maturational timing, and fertility; (3) individual-level correlations between this same set of factors; and (4) natural experiments leveraging the impact of externally caused changes in mortality on LH traits. Partially supporting each model, we found that harsh conditions encompassing energetic stress and ambient cues to EM (external cues received through sensory systems) have countervailing effects on the development of LH strategies, both delaying pubertal maturation and promoting an accelerated pace of reproduction and higher offspring number. We conclude that, although energetics are fundamental to many developmental processes, providing a first tier of environmental influence, this first tier alone cannot explain these countervailing effects. An important second tier of environmental influence is afforded by ambient cues to EM. We advance a two-tiered model that delineates this second tier and its central role in regulating the development of LH strategies. Consideration of the first and second tier together is necessary to account for the observed countervailing shifts toward both slower and faster LH traits.

Our target article proposed that vertebrates, cephalopod mollusks, and euarthropods independently converged onto high levels of brain and cognitive complexity and that this macroevolutionary trend was coupled with and facilitated by the acquisition of a small set of pivotal traits, used in visuomotor control of three-dimensional and targeted movements. In response to commentaries that challenged our working premise and conclusions, we (1) use the concept of aggregate complexity to define brain and cognitive complexity and dispel misconceptions about anthropocentric bias, (2) call attention to the explanatory value and power of convergence as an important evolutionary concept, (3) highlight certain architectural and organizational features of the nervous system as scaffolds for the evolutionary expansion of behavioral and cognitive complexity, and (4) consider the phylogenetic distribution of phenomenal consciousness in relation to our findings. We also try to foster a greater appreciation for cognition as a process that involves whole animals as aggregate systems and that requires an extended repertoire of laws and principles to understand its evolution.

The impact the body has upon complex cognitive capabilities has long challenged cognitive scientists. Insights into the complex interplay between how we see, what we see, and how we interpret what we think we saw and remembered are offered by a surprising source: the effects magicians create.

Collating the neural traits possessed by taxa provides valuable evidence about brain evolution. However, to get the full scientific benefit, we must pair it with an understanding of the selection pressures driving brain complexity. This can be achieved by considering the heterogeneity of the animal’s environment alongside the reliability of information. A complex environment selects for a complex brain.

We argue that cognitive evolution is rooted in the development of distributed functional internal models within hierarchical, decentralized, and multimodal sensorimotor loops. Based on an embodied cognition perspective, we emphasize how these models initially evolved to support adaptive behavior and can be flexibly recruited for higher cognitive functions. This perspective complements the proposed sensory-driven and vision-centric account.

Given its assumption that cognition is embodied, the multitrait framework could benefit from engaging with recent work in embodied cognitive science. Here, we introduce three lines of contemporary research—from ecological psychology, basal cognition, and embodied cognitive neuroscience—which help contextualize the article’s “trait-linkage” findings and further support the authors’ arguments for evolutionary continuity between simple and complex cognitive traits.

In canvassing the animal kingdom for cognitive capacity by a multitrait approach, much hinges on how traits are operationally defined. In my commentary, I call attention to problematic aspects of the perspective on learning, a central component of cognition, adopted by Coombs and Trestman in their phylogenetic survey of cognitive capacity.

This commentary integrates Coombs and Trestman’s trait-linkage hypothesis with Teufel and Fletcher’s neurocomputational predictive framework to propose that high-resolution visual systems operate as intrinsic bottom-up predictive mechanisms. By merging these concepts, we emphasize the significance of early sensory prediction in perception and provide a biologically inspired foundation for developing more adaptive, embodied, and cognitively resilient artificial intelligence (AI) systems.

It is argued that there are huge differences between species of the “advanced” three phyla, both cognitively and neurally, and that more sophisticated attributes than vision and motion characterize only a few of them, and these are mainly found in vertebrates. Especially with respect to learning and memory, only some vertebrate species may possess sophisticated memory processing abilities.