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Honest signals have long posed a challenge for evolutionary biologists to explain. Here we propose a new and general, fully Darwinian theory of signalling, Signalling Trade-Off Theory, to explain both honest and dishonest signalling based on recent theoretical and experimental developments. The leading explanation for honest signalling for decades has been the Handicap Principle, which assumes that signals are honest because they are costly, providing an explanation admittedly out of the scope of Darwinian selection. However, its mainstream acceptance was based on misinterpretations of early signalling models. These models, contrary to common interpretations, show that signals are honest not because of their inherent absolute costs (handicaps), but because underlying life-history trade-offs ensure that cheating is costly. Trade-offs, unlike costs, can fully represent both sides of an investment over different timescales arising in Darwinian systems. Here, we summarize the lines of evidence that fully refute the Handicap Principle – and the related Costly Signalling paradigm – and we examine the alternative hypotheses proposed to explain honest signalling. We show that these hypotheses all involve trade-offs at some level, but they failed to recognize the importance of trade-offs for explaining honesty. We then examine more recent theoretical models that demonstrate that signalling trade-offs maintain honesty, even without signalling costs (handicaps) at the evolutionary equilibrium. Moreover, we show that differential trade-offs are both necessary and sufficient to explain honest signals in cases with conflict of interest. Based on these advances, we argue that differential signalling trade-offs provide not only a general evolutionary explanation for both dishonest and honest signals but also unifies earlier proposals. Finally, we demonstrate that short-term investments under trade-offs at the proximate level (once considered handicap mechanisms) can result in long-term fitness benefits, which thus integrates proximate and evolutionary explanations for signal honesty. We also address how results from sexual selection studies (e.g., terminal investment) are consistent with our theory.

Losses of genetic diversity have traditionally been monitored using genealogical information through the coefficient of inbreeding (F), defined as the probability that two alleles at a locus are identical-by-descent (IBD).

The coefficient F should be informative on the accumulation of lethal recessive variants in small populations, where mating between relatives is unavoidable. Drift can rapidly increase the frequency of deleterious alleles, potentially compromising the viability of both individuals and populations. Consequently, when molecular information is available, estimating autozygosity (homozygosity resulting from IBD) becomes a central concern in conservation programmes.

However, the extent to which F is reflected in the genome remains unclear. Unlike genealogical parameters, molecular-based estimates of inbreeding are subject to finite sampling. Therefore, homozygosity at a locus can occur by chance with alleles being identical-by-state (IBS) rather than IBD. As a result, molecular estimates of homozygosity usually differ substantially from genealogical expectations making difficult their interpretation. Mendelian sampling and demographic factors may contribute to these discrepancies.

In this presentation, we review genealogical approaches for assessing the increase in inbreeding due to population deviation from the Wright-Fisher idealized model We then illustrate discrepancies between genealogical F and molecular-based estimates of inbreeding using published information from a short pedigree of the extremely endangered Gochu Asturcelta pig breed.

Finally, we present two subsets of our Gochu Asturcelta pedigree differing in the genomic composition of the Base Population: a “fully heterozygous” subset and an “opposite homozygous” subset. These contrasting scenarios illustrate how Mendelian sampling darkens the relationship between genealogical inbreeding and autozygosity.

Improving livestock productivity, resilience and sustainability require the effective integration of animal breeding and genetics with modern reproductive technologies. The Joint FAO/IAEA center supports Member States in applying nuclear and nuclear related technologies that ensure genetic improvement, reproductive efficiency and the sustainable utilization and conservation of indigenous animal genetic resources. This presentation will provide an overview of the work of the IAEA Animal Production and Health Laboratory in two closely interconnected areas: animal breeding and genetics and Assisted Reproductive Technologies (ART). In animal breeding and genetics, the work focuses on the application of molecular techniques in locally adapted breeds to support the selection of animals with desirable production, adaptation and resilience traits for more effective and sustainable breeding programmes. It will also highlight ART application, including artificial insemination, semen evaluation and cryopreservation, in vitro embryo production (IVEP) and their importance for long-term conservation of valuable genetics. The focus will be on the important component of the IAEA's work in the transfer of these technologies and expertise to Member States and how genetics, genomics and assisted reproduction can be integrated into a comprehensive approach to improve local breeds, while supporting their conservation and sustainable utilization to address future challenges in food security and animal production.

Urbanisation is changing the face of our planet in an ever enhancing pace. With it comes big change for wildlife. Natural habitats are being destroyed or fragmented, air and soil are getting polluted, the night is illuminated, the quiet is ensonified, and humans are everywhere, all the time. How can wild animals deal with these challenges? Some species don’t manage at all. Others adjust their biology. My group studies such adjustments on the small mammal community, that is, on mice and shrews. We found ecological effects such as changed community compositions; behavioural adjustments such as altered circadian activity rhythms, foraging patterns and personality strategies; and physiological effects such as an altered metabolic rate and changed hormonal stress responses. During my talk, I will present a selection of our results and will try to convince you that the hidden life of wild small mammals is worth a closer look.

Parasites are among the most diverse and abundant forms of life on Earth, yet we are often blind to their dynamics within hosts. To parasites, hosts represent rare and hostile microhabitats. As hosts must cope with increasingly stressful environments in the face of climate change, we know little about how multiple stressors interact to shape infection outcomes. During this talk, we will explore how anthropogenic stressors such as urbanization and warming shape host-parasite dynamics in two vastly different systems: the fungal pathogen Batrachochytrium dendrobatidis and its amphibian hosts, and the tapeworm Schistocephalus solidus and its first intermediate host, a freshwater copepod. By embracing biological variation across systems and the trade-offs that shape disease dynamics, we gain traction on which rules are system-specific and which generalize across the ecology and evolution of disease in a changing world.

Ancient proteins are transforming our ability to investigate human and animal evolution, extending biomolecular research far beyond the limits of ancient DNA. Proteins can survive in fossils that are too old, too degraded, or otherwise unsuitable for genomic analysis. This talk will explore how the field of “palaeoproteomics" is opening new windows onto the human past, from the discovery and identification of elusive hominin fossils to reconstructing biodiversity through deep time.

The two hemispheres of the vertebrate brain are functionally not equivalent. For many higher cognitive functions, one hemisphere is faster and/or more accurate than the other in the majority of individuals. The most widely investigated phenotypes in human subjects research are handedness and language lateralization. While tremendous advances have been made in understanding genetic and epigenetic factors involved in determining left‐handedness, most of the variance in behavioral data remains unexplained. In particular, the link between genetic and epigenetic factors to brain structure and ultimately to behavior remains not well understood in the human brain. Several ideas have been proposed to overcome this issue. First, research on left‐right asymmetries in brain and behavior needs stronger cross‐species integration. Research in human participants and research in animal model species are often isolated. However, both research areas could strongly benefit from each other. For example, results of recent meta‐analyses in animals highlight similarities and differences to human handedness. Second, research on left‐right asymmetries in brain structure needs to focus on a broader range of phenotypes. In research on human participants, the most widely used brain structural phenotypes are macrostructural aspects such as the volume or surface area of specific regions. However, the amount of variance in behavioral phenotypes explained by such macrostructural features is very small. Recent research suggests that also integrating microstructural phenotypes obtained by advanced diffusion imaging techniques such as NODDI may be helpful in linking behavioral phenotypes to brain structure. Third, the commonly used behavioral phenotypes handedness and language lateralization may not be optimal for comparative research as they both show a uniquely skewed distribution in humans. Comparative research on left‐right asymmetries in the brain would strongly benefit from using a broader range of phenotypes, including social laterality.

Elephants possess a rich vocal repertoire anchored by infrasonic rumbles used across social contexts, including as long‑distance contact calls. What makes elephants’ vocal communication distinctive is their remarkable vocal plasticity: they flexibly route sound production (oral vs. nasal), employ velopharyngeal coupling, and can generate biphonation by simultaneously emitting nasal and oral components. They also produce both common and idiosyncratic sounds by modulating non‑phonatory structures, broadening their communicative frequency range. Alongside a few other mammals, elephants show vocal production learning—experience‑based modifications of call structure—which helps explain their context sensitivity and signal flexibility and offers comparative insight into open‑ended vocal systems.

This talk synthesizes two decades of zoo and field work on African savanna (Loxodonta africana) and Asian elephants (Elephas maximus), covering sound‑production mechanisms, individual and contextual drivers of acoustic structure, and the adaptive functions of key call types. I will also present first results on multimodal communication in greeting contexts, describing how vocalizations are coordinated with trunk, ear, and head movements, and defining intentional gestures—flexible, recipient‑directed, and apparently goal‑oriented signals.

Finally, I will highlight advances in applying artificial intelligence to elephant bioacoustics. Our primary objective is to develop a computational model that identifies acoustic cues relevant to elephant communication through a combined data‑ and knowledge‑driven approach. This includes sound synthesis, pattern mining, and sound recognition, implemented in lab‑based computational simulations and field experiments that iterate between model refinement and empirical validation. The goal is to understand not only what elephants communicate, but also how they encode vocal information. I will outline how these tools translate into conservation practice: supporting population monitoring and mitigating human–elephant conflict through early‑warning and information systems.

How do organisms develop the ability to solve physical problems? While adult-centric models dominate comparative cognition, I advocate for an ontogenetic perspective to investigate how motor and exploratory routines are functionally organised during development to construct physical intelligence. Specifically, across human infants, non-human primates, and diverse avian models, I investigate the cognitive and executive mechanisms that shape physical intelligence. I address whether early performance limitations in means-end coordination and tool-related tasks reflect fundamental causal deficits or, instead, developmental constraints—such as lateral motor prepotencies—that require the maturation of inhibitory control to be overcome. Furthermore, I examine the developmental role of spontaneous exploration, questioning whether technical proficiency relies on genetically canalised attention toward functional precursors or, conversely, is constructed through the progressive, experience-dependent integration of domain-general intelligence.

Animals depend on the dietary intake of essential biomolecules such as vitamins, amino acids, and fatty acids. Differences in the availability of these nutrients in prey lead consumers to adopt diverse strategies to meet their physiological needs. In this talk, I present research on how human‑induced changes in aquatic ecosystems influence the food quality available to wild salmonid fishes, and how this affects their behavioural adaptations and ecological performance. I will show how individual fish navigate the trade-offs between what their bodies require and what is available in the streams they inhabit. Drawing on examples from both experimental and field studies, the talk will outline broader implications for behavioural ecology and the conservation of wild fish populations.

Under unprecedented environmental change, organisms depend on rapid and flexible responses achieved through phenotypic plasticity, rather than on slower genetic adaptation. However, the mechanisms underlying plasticity - and how it can be quantified, predicted, and preserved - remain largely unresolved. This uncertainty continues to fuel debate about the adaptive value and evolutionary relevance of phenotypic plasticity. Yet plasticity is a critical determinant of species persistence and their capacity to cope with environmental change in the Anthropocene.

In this talk, I will examine how physiological, molecular and epigenetic mechanisms shape avian responses to environmental change. First, I will outline key physiological and molecular mechanisms that mediating individual coping abilities - from the reinterpretation of “stress hormones” to the long-lasting effect of early-life conditions. Second, I will discuss how epigenetic mechanisms can act as upstream regulators of these processes, contributing to rapid and adaptive responses to environmental change. Finally, I will present recent findings supporting the role of “epigenetic potential for DNA methylation” as a heritable trait associated with phenotypic plasticity and coping capacity.