I argue that the two-tier model represents a clear step forward, resolving debates and disentangling complexity in our understanding of human life history strategies. I relate the model to findings from my previous work, as well as to embodied capital and market integration, providing relevant schematics. I then discuss the timing of exposure to mortality cues and the age of the deceased, discussing what the two-tier model does and does not add to these debates.

The relationship between local extrinsic mortality rates and the timing of life-history milestones can be better understood when examined through food environments rather than by population “types,” like small-scale societies or high-income countries. By mapping observed life-history variation onto food environments, which mediate the fundamental relationship between mortality and fertility, the explanatory value of a 2-tiered model becomes less compelling.

In response to recent arguments for a one-tiered model of life-history development, Ellis and colleagues present a two-tiered model that integrates energetics with development. Early formulations of this model were, however, already two-tiered. The target article separates itself from earlier work by digging deeper into the underlying energetics assumption and how it transacts with ambient cues to impact development.

In this commentary, I highlight the challenge of incorporating the harshness–unpredictability framework into the two-tiered model. While the effects of energetic stress (first tier), which are mostly mediated through biological pathways, can be decomposed into harsh (high mean) and unpredictable (high variance) components, ambient cues to EM (second tier) blur this distinction because they often share the same psychological mediators.

We evaluated large language model (LLM)-based agents integrated with the electronic medical record to assess blood culture appropriateness. While sensitivity was high, specificity remained low. Performance was shaped by prompt phrasing, sycophantic behavior, and semantic triggers, reflecting both the potential and limitations of LLMs in real-world clinical decision support.

This commentary complements Ellis et al.’s two-tiered framework by using panel data and emphasizing the role of population density in decelerating life history (LH) strategy. We show that mortality cues and energetic constraints do not operate in isolation, demonstrating how density-dependent competition shapes LH strategies over time and underscoring the need for a dynamic, multifaceted approach to LH development.

Ellis and colleagues propose that plasticity in human life history strategy (pubertal timing, reproductive pacing) is governed by energetic and mortality-cue related regulatory tiers. We feel that our published interpretation of these findings – that growth (and thus maturational timing) is energetically driven, while reproductive behaviors are largely free to vary independent of energetics – provides a more parsimonious interpretation of this work. The concept of tiers is mechanistically vague and introduces unnecessary complexity to this literature.

The two-tiered model proposed by Ellis et al. offers a compelling framework for understanding how extrinsic mortality (EM) sources shape life history strategies, including fertility. This commentary evaluates this model in light of modern fertility trends, identifies gaps in its current formulation, and proposes modifications to enhance its explanatory power in modern contexts.

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.

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.

Double aortic arch is a congenital vascular ring with tracheal and oesophageal compression, potentially causing stridor and dysphagia. While some recommend early surgery, others favour observation. We present a 7-week-old female with mild symptoms and prenatally diagnosed double aortic arch who suffered cardiac arrest, highlighting the need for early surgery in patients with vascular rings and airway or oesophageal compression.

The anomalous origin of the right pulmonary artery from the ascending aorta is a rare congenital anomaly usually diagnosed in infancy. When diagnosed later during adolescence, it presents diagnostic and treatment challenges, especially in determining whether pulmonary vascular disease can be reversed. We report the case of an 11-year-old girl who experienced increasing fatigue and was diagnosed with anomalous origin of the right pulmonary artery from the ascending aorta through echocardiography, CT angiography, and cardiac catheterisation. Segmental pulmonary hypertension was noted, but the operability was uncertain. A new non-invasive test combining 2D phase-contrast cardiac MRI with inhaled iloprost was performed. Flow measurements revealed a 42% rise in right pulmonary artery flow, indicating preserved vasoreactivity. Lung biopsy confirmed pulmonary vascular changes consistent with Heath–Edwards Stage II–III. Based on these findings, surgical reimplantation of the anomalous artery into the main pulmonary artery was performed. The postoperative recovery after surgery was uneventful, and follow-up catheterisation demonstrated normalised haemodynamics without residual stenosis. This case highlights the potential value of cardiac MRI–based vasoreactivity testing with inhaled iloprost as an additional tool alongside standard diagnostics for evaluating operability in late-presenting anomalous origin of the right pulmonary artery from the ascending aorta. Combining imaging, histopathology, and haemodynamic data allowed a personalised and safe surgical approach.

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.

Non-suicidal self-injury (NSSI) among adolescents severely jeopardizes their well-being and has emerged as a significant global public health challenge. However, research on the trends in NSSI among adolescents remains scarce. This study sought to uncover the evolving patterns in the severity of NSSI among adolescents and the factors that influence these patterns. The Deliberate Self-Harm Inventory was employed to measure the severity of NSSI among adolescents. Relevant studies were retrieved from both Chinese databases (CNKI, Wanfang, and VIP) and English databases (Web of Science, PubMed, Scopus, ProQuest, and Wiley). A total of 70 articles (71 studies; N = 96,382) were included in this review. The data spanned from 2007 to 2023. The analysis revealed the following: (1) Although the severity of NSSI showed a small to moderate upward trend from 2007 to 2023, this increase did not reach statistical significance. (2) No significant differences in trends were observed among Asia, Europe, and the America. (3) Adolescents with clinical samples exhibited a more pronounced upward trajectory in NSSI severity compared to those with non-clinical samples. (4) Social development indicators (GDP per capita, Human Development Index, and Internet penetration rate) and social well-being (happiness index) exhibited significant positive correlations with NSSI among adolescents. Conversely, lower social equity (higher Gini coefficient) was associated with reduced NSSI among adolescents. This study elucidated the changing trends in NSSI among adolescents and offered novel insights for the early prevention and individualized intervention of NSSI among adolescents.

The Syrian government’s violent suppression of pro-democracy protests in March 2011 sparked a civil war that resulted in the deaths of hundreds of thousands of people and the displacement of millions. This study focuses on the emotional achievement of 357 Syrian primary and secondary school students who have moved to Türkiye and are under temporary protection. The researchers used the achievement emotion scale to collect data. They conducted a t-test, analysis of variance, correlation analysis and multiple linear regression to examine the sociodemographic factors affecting students’ achievement emotions. The results revealed that boy students experienced more negative achievement emotions than girl students, and that the longer the students have been in temporary protection, the more their positive achievement emotions have decreased. The ongoing war in Syria has dire consequences for school-age children who have been forced to flee their homes.

The two-tiered life history (LH) model proposes that different sources of extrinsic mortality (EM) have opposing effects that regulate development toward both slower and faster LH traits. Although the 53 commentators generally endorsed the two-tiered model and empirical conclusions of the target article, the devil is in the details. Some commentators challenged model assumptions (e.g., the mechanistic basis of the two-tiered model; whether the model is genetically confounded; the relative importance of child versus adult mortality). Other commentators proposed extensions/modifications of model concepts and hypotheses (e.g., incorporating density-dependent regulation; use of formal models to generate and test hypotheses; connection to the internal predictive adaptive response [PAR] model). In this reply, we review and address these challenges and proposed extensions/modifications. We hope that this iterative process advances our understanding of the complexity of EM, its opposing tiers, and their dualistic effects–both hierarchical and countervailing–on variation in human life histories.

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.