Charles Darwin in the last paragraph of the Origin of Species described interactions between organisms as a tangled bank. In his beautiful description interactions between organisms were restricted to competition, mutualism, and other forms of symbiosis. Natural selection was based on the “strong principle of inheritance” taking place only within lineages. In contrast, the wealth of genetic information acquired in recent years provides an even more complex picture. Bacterial, archaeal and many eukaryotic lineages frequently exchange genes, making the genomic information accessible to members of a species much larger than the genome of an individual. Due to the transfer of genetic information, the phylogeny of genomes is embedded in a web formed by transfers of genes and parts of genes. Some hold out hope that the main strands in the genes’ histories reflect the tree of cells. However, highways of gene sharing, transfer biases, within-gene recombination, and transfers from now extinct or unsampled lineages make inferring the tree of cells a problematic enterprise. Many assume that natural selection acts on small changes occurring within a population; however, selection occurs at multiple levels ranging from selfish genetic elements to groups of organisms belonging to the same or to different species. Many changes associated with genetic exchange dramatically change the phenotype of an organism opening new ecological niches. In addition, Constructive Neutral Evolution has generated complexity not because the complexity and associated traits were beneficial, but rather the genetic changes were not sufficiently detrimental to be subject of purifying selection and once fixed could not be easily removed.
Environmental gradients can promote divergence in reproductive strategies, but it remains unclear whether different reproductive traits respond consistently to the same environmental variation. Elevational gradients provide particularly useful systems for addressing this question because climatic conditions change sharply over relatively short geographic distances. In this study, we examined reproductive variation across six populations of the lacertid lizard Psammodromus algirus spanning a 2200-m elevational gradient in the Sierra Nevada (SE Spain). We quantified reproductive timing, capture-to-oviposition time, clutch size, mean egg mass, relative clutch mass, and estimated lifetime egg production. Reproductive traits showed three contrasting elevational responses. First, reproductive phenology varied with elevation: high-elevation females became gravid earlier and showed longer capture-to-oviposition time, patterns consistent with mechanisms that may partially offset thermal constraints in cold environments. Relative clutch mass tended to increase with elevation. Second, clutch size and egg mass increased with elevation, but these patterns disappeared after controlling for maternal body size, indicating that elevational variation in these traits was mediated by variation in maternal body size. Third, mean laying date remained invariant across elevations. Our exploratory estimates of lifetime egg production suggest marked differences among populations, with particularly high values at alpine sites, potentially reflecting important elevational differences in demographic structure. Comparison with other studies further suggests that such heterogeneity is widespread among lizards, implying that elevational gradients do not generate uniform reproductive responses. Overall, the reproductive response to elevation was trait-dependent, with pronounced elevational variation in some components of reproduction but little or no variation in others.
This article explores the role of material innovation as a central force in human evolution, framing it within niche construction theory (NCT) as originally developed by Odling-Smee, Laland, and Feldman, extended into archaeology and anthropology by Laland, O’Brien, and others, and philosophically enriched by Kim Sterelny’s work on environmental scaffolding and epistemic engineering. Rather than opposing NCT to gene-centred or adaptationist approaches as if they were uniformly reductionist, the article treats NCT as a complementary framework that foregrounds ecological inheritance, organism-environment feedback, and material scaffolding. It also addresses debates over whether NCT constitutes a fundamental revision of evolutionary theory or a powerful heuristic within an expanded Darwinian framework. I argue that humans have actively reshaped their selective environments through cumulative technological and cultural practices, although the scale, intensity, and form of this reshaping vary substantially across populations, ecologies, and historical periods. From stone tools and fire to metallurgy, shelter, medicine, and neural interfaces, material innovations have functioned as developmental and selective scaffolds that fundamentally transformed both our cognitive architecture and biological fitness. Drawing on Sterelny’s concepts of the scaffolded mind and the evolved apprentice, I show how tools, artifacts, and institutions constitute inherited features of the human niche, guiding learning and enabling high-fidelity cultural transmission. The paper traces this co-evolutionary dynamic across historical phases of innovation, illustrating how technological scaffolds have not only relaxed certain selection pressures but also introduced new ones, often accelerating evolutionary change. At the same time, I distinguish among mechanisms with strong genetic evidence, plausible but weakly documented hypotheses, and cases that are better interpreted as phenotypic plasticity, cultural change, or ecological alteration rather than demonstrated genetic adaptation. I close by considering the ethical and philosophical implications of intentional niche construction in the context of emerging technologies like genetic engineering and brain–computer interfaces. In an era where humans increasingly shape the conditions of their own evolution, understanding material innovation as an evolutionary driver is crucial for both philosophy of biology and responsible technological governance.
The masticatory system plays a key role in ecological adaptation. In grey wolves (Canis lupus), intraspecific variation in jaw muscle architecture and divergence from domestic dogs (Canis familiaris) remain poorly documented due to limited access to specimens. Here, we present the first large-scale quantitative analysis of jaw-closing muscles in wolves, based on dissections of 112 individuals from France (C. l. italicus, n = 98) and North America (C. l. nubilus, n = 14), compared with 86 domestic dogs. Muscle mass, fiber length, and pennation angle were measured to estimate physiological cross-sectional area (PCSA), a proxy for maximal muscle force. In French wolves, males exhibited greater absolute muscle mass and PCSA than females, but no differences in relative muscle proportions, indicating size-related scaling rather than shape dimorphism. No significant differences were detected between European and North American wolves, consistent with stabilizing selection maintaining a functionally ‘optimal’ masticatory design. In contrast, wolves displayed greater jaw-adductor mass and PCSA than dogs. Interestingly, large molossoid breeds overlapped with wolves, reflecting functional convergence under artificial selection for attack or defense. Together, these results show that wolf masticatory architecture is constrained by selection for large-prey predation, whereas domestication relaxes and can secondarily reimpose these functional demands.
Evolutionary biologists commonly use landmark-based geometric morphometrics to characterize and compare biological shapes. Advances in three-dimensional imaging hold potential to catapult morphometric studies, but quantifying shape from 3D surfaces efficiently remains challenging. Several surface-only morphometric procedures have been proposed, which align surfaces to one another and use their differences as the basis of shape quantification and analysis. Comparisons of landmark-based and surface-only methods for specific datasets have revealed mixed results, but these studies utilized empirical datasets where the true patterns of shape differences are unknown. In this study we performed a simulation experiment where the true shape differences between objects were known, and evaluated the performance of two landmark-based and four surface-only methodologies under these conditions. Several procedures, including landmarks plus semilandmarks, as well as the surface-only method DAA (and to a lesser extent auto3d), most consistently recovered the known patterns of shape variation. Results from other surface-only procedures (GPSA and pseudoLM) were more variable. Notably, patterns in more complex shapes were better characterized than patterns in simpler shapes, implying that automated surface-only methods were challenged when presented with shapes whose principal axes were similar, or where structures contained few localized shape differences for these methods to properly orient the surfaces. Overall, our findings highlight that while biologically informed landmarking remains imperative as a foundation for morphometric analyses, some surface-only procedures do offer a powerful and efficient means of characterizing shape, and hold promise for morphometric studies.
