Insights into the palaeobiology of an early Homo infant: multidisciplinary investigation of the GAR IVE hemi-mandible, Melka Kunture, Ethiopia

Childhood is an ontogenetic stage unique to the modern human life history pattern. It enables the still dependent infants to achieve an extended rapid brain growth, slow somatic maturation, while benefitting from provisioning, transitional feeding, and protection from other group members. This tipping point in the evolution of human ontogeny likely emerged from early Homo. The GAR IVE hemi-mandible (1.8 Ma, Melka Kunture, Ethiopia) represents one of the rarely preserved early Homo infants (~ 3 years at death), recovered in a richly documented Oldowan archaeological context. Yet, based on the sole external inspection of its teeth, GAR IVE was diagnosed with a rare genetic disease–amelogenesis imperfecta (AI)–altering enamel. Since it may have impacted the child’s survival, this diagnosis deserves deeper examination. Here, we reassess and refute this diagnosis and all associated interpretations, using an unprecedented multidisciplinary approach combining an in-depth analysis of GAR IVE (synchrotron imaging) and associated fauna. Some of the traits previously considered as diagnostic of AI can be better explained by normal growth or taphonomy, which calls for caution when diagnosing pathologies on fossils. We compare GAR IVE’s dental development to other fossil hominins, and discuss the implications for the emergence of childhood in early Homo.

The psychological foundations of reputation-based cooperation

Humans care about having a positive reputation, which may prompt them to help in scenarios where the return benefits are not obvious. Various game-theoretical models support the hypothesis that concern for reputation may stabilize cooperation beyond kin, pairs or small groups. However, such models are not explicit about the underlying psychological mechanisms that support reputation-based cooperation. These models therefore cannot account for the apparent rarity of reputation-based cooperation in other species. Here, we identify the cognitive mechanisms that may support reputation-based cooperation in the absence of language. We argue that a large working memory enhances the ability to delay gratification, to understand others' mental states (which allows for perspective-taking and attribution of intentions) and to create and follow norms, which are key building blocks for increasingly complex reputation-based cooperation. We review the existing evidence for the appearance of these processes during human ontogeny as well as their presence in non-human apes and other vertebrates. Based on this review, we predict that most non-human species are cognitively constrained to show only simple forms of reputation-based cooperation. This article is part of the theme issue ‘The language of cooperation: reputation and honest signalling’.

The psychological foundations of reputation-based cooperation

Humans care about having a positive reputation, which may prompt them to help in scenarios where the return benefits are not obvious. Various game-theoretical models support the hypothesis that concern for reputation may stabilize cooperation beyond kin, pairs or small groups. However, such models are not explicit about the underlying psychological mechanisms that support reputation-based cooperation. These models therefore cannot account for the apparent rarity of reputation-based cooperation in other species. Here we identify the cognitive mechanisms that may support reputation-based cooperation in the absence of language. We argue that a large working memory enhances the ability to delay gratification, to understand others' mental states (which allows for perspective-taking and attribution of intentions), and to create and follow norms, which are key building blocks for increasingly complex reputation-based cooperation. We review the existing evidence for the appearance of these processes during human ontogeny as well as their presence in non-human apes and other vertebrates. Based on this review, we predict that most non-human species are cognitively constrained to show only simple forms of reputation-based cooperation.

Insights into the uniquely human origins of understanding other minds

We summarize research and theory to show that, from early in human ontogeny, much information about other minds can be gleaned from reading the eyes. This analysis suggests that eyes serve as uniquely human windows into other minds, which critically extends the target article by drawing attention to what might be considered the neurodevelopmental origins of knowledge attribution in humans.

What About Culture and Development?

Across cultures, self-serving interests tends to be considered as wrong or bad, negatively evaluated, and reprehensible. All children are exposed to this norm even if, in some human societies, this norm is expressed in paradoxical individualistic ways. Attached to this fundamental and universal ethics law is the subjective sense of fairness, what individuals consider their right share of the resources and what they are entitled to. Fairness pertains to the strong, often elusive sense we have of who deserves what and why in relation to others. As elusive as it might be, this sense is manifest remarkably early in development. And this is true regardless of vastly different social and cultural environments. In human ontogeny and across cultures, from five years of age, individuals from all cultures have developed all the basic ingredients to face and deal with others’ as well as their own moral conundrums. They step right into the main plot of the human drama that, from time immemorial, plays out in myths, oral tales, and tragic representations across all human cultures.

Indexical Ways of Knowing: An Inquiry Into the Indexical Sign and How to Educate for Novelty

In this paper, I propose that the indexical sign can be used to derive a model for active (touching-and-feeling) learning. The implicit processes involved in the subtle reading of indices contain explanatory possibilities for understanding how students adapt to novelty in the learning process. Besides looking at how indexicality functions in human ontogeny and cognition, I will also examine the human capacity for modeling our world through aggregations of systems of representations (Sebeok, 1994). Modeling systems (with their implicit recognition that the human is a semiotic animal) help us to conceptualize how novelty is assimilated in the learning process. I posit that how we come to terms with new experiences (and new stimuli generally) is of an indexical nature. I am specifically referring to the site where "the new" comes from the outside (like a rain cloud signaling the coming storm) and acts upon us. We can recognize the rain cloud as an experiential pattern (as a semiotic entity) or not; the rain is still going to bear down on us regardless of the success of our interpretations. This existential realness of indexical signs is precisely their power to function as a pedagogical tool, to help us assimilate and accommodate to novel stimulus. The concept of modeling helps us conceptualize the process in which the new stimulus is absorbed and integrated into our cultural/semiotic systems. In short, this paper aims to explore what I call the indexical rub of learning; that initial friction or resistance felt when meeting a new experience. My hope is that this exploration can aid in the cultivation of a mindset in teachers, students and researchers that does not fear this resistance, but can use it to propel positive absorption (in the Deweyian sense) and engaged learning.

Are all distances created equal? Insights from developmental psychology

Gilead et al.'s theory presupposes that traversing temporal, spatial, social, and hypothetical distances are largely interchangeable acts of mental travel that co-occur in human ontogeny. Yet, this claim is at odds with recent developmental data suggesting that children's reasoning is differentially affected by the dimension which they must traverse, and that different representational abilities underlie travel across different dimensions.

Brain Plasticity in Human Lifespan Development: The Exploration–Selection–Refinement Model

Plasticity can be defined as the brain's capacity to achieve lasting structural changes in response to environmental demands that are not fully met by the organism's current functional capacity. Plasticity is triggered when experiential forces interact with genetic programs in the maturation of species-common functions (e.g., vision), but it is also required for less universal forms of learning that sculpt individuals into unique members of their species. Hence, delineating the mechanisms that regulate plasticity is critical for understanding human ontogeny. Nevertheless, mechanisms of plasticity in the human brain and their relations to individual differences in learning and lifespan development are not well understood. Drawing on animal models, developmental theory, and concepts from reinforcement learning, we introduce the exploration–selection–refinement (ESR) model of human brain plasticity. According to this model, neuronal microcircuits potentially capable of implementing the computations needed for executing a task are, early in learning, widely probed and therefore structurally altered. This phase of exploration is followed by phases of experience-dependent selection and refinement of reinforced microcircuits and the concomitant gradual elimination of novel structures associated with unselected circuits. The ESR model makes a number of predictions that are testable in humans and has implications for the study of individual differences in lifespan development.