Making use of Capuchins’ behavioral propensities to obtain hair samples for DNA analyses

Genotyping wild and captive capuchins has become a priority and hair bulbs have high quality DNA. Here, we describe a method to non-invasively collect fresh-plucked strands of hair that exploits capuchins’ manual dexterity and propensity to grasp and extract food. The apparatus consists of a transparent tube baited with food. Its extraction requires the monkey to place its forearm in contact with double-sided tape applied on the inner surface of the tube entrance. The “tube” method, successfully implemented with captive (N=23) and wild (N=21) capuchins, allowed us to obtain hair bulbs from most individuals and usable genomic DNA was extracted even from a single bulb

On the psychological origins of tool use

The ubiquity of tool use in human life has generated multiple lines of scientific and philosophical investigation to understand the development and expression of humans' engagement with tools and its relation to other dimensions of human experience. However, existing literature on tool use faces several epistemological challenges in which the same set of questions generate many different answers. At least four critical questions can be identified, which are intimately intertwined-(1) What constitutes tool use? (2) What psychological processes underlie tool use in humans and nonhuman animals? (3) Which of these psychological processes are exclusive to tool use? (4) Which psychological processes involved in tool use are exclusive to Homo sapiens? To help advance a multidisciplinary scientific understanding of tool use, six author groups representing different academic disciplines (e.g., anthropology, psychology, neuroscience) and different theoretical perspectives respond to each of these questions, and then point to the direction of future work on tool use. We find that while there are marked differences among the responses of the respective author groups to each question, there is a surprising degree of agreement about many essential concepts and questions. We believe that this interdisciplinary and intertheoretical discussion will foster a more comprehensive understanding of tool use than any one of these perspectives (or any one of these author groups) would (or could) on their own

Indentation as a Technique to Assess the Mechanical Properties of Fallback Foods

A number of living primates feed partyear on seemingly hard food objects as a fallback. We ask here how hardness can be quantified and how this can help understand primate feeding ecology. We report a simple indentation methodology for quantifying hardness, elastic modulus, and toughness in the sense that materials scientists would define them. Suggested categories of fallback foods—nuts, seeds, and root vegetables— were tested, with accuracy checked on standard materials with known properties by the same means. Results were generally consistent, but the moduli of root vegetables were overestimated here. All these properties are important components of what fieldworkers mean by hardness and help understand how food properties influence primate behavior. Hardness sensu stricto determines whether foods leave permanent marks on tooth tissues when they are bitten on. The force at which a food plastically deforms can be estimated from hardness and modulus. When fallback foods are bilayered, consisting of a nutritious core protected by a hard outer coat, it is possible to predict their failure force from the toughness and modulus of the outer coat, and the modulus of the enclosed core. These forces can be high and bite forces may be maximized in fallback food consumption. Expanding the context, the same equation for the failure force for a bilayered solid can be applied to teeth. This analysis predicts that blunt cusps and thick enamel will indeed help to sustain the integrity of teeth against contacts with these foods up to high loads

Indentation as a Technique to Assess the Mechanical Properties of Fallback Foods

A number of living primates feed partyear on seemingly hard food objects as a fallback. We ask here how hardness can be quantified and how this can help understand primate feeding ecology. We report a simple indentation methodology for quantifying hardness, elastic modulus, and toughness in the sense that materials scientists would define them. Suggested categories of fallback foods—nuts, seeds, and root vegetables— were tested, with accuracy checked on standard materials with known properties by the same means. Results were generally consistent, but the moduli of root vegetables were overestimated here. All these properties are important components of what fieldworkers mean by hardness and help understand how food properties influence primate behavior. Hardness sensu stricto determines whether foods leave permanent marks on tooth tissues when they are bitten on. The force at which a food plastically deforms can be estimated from hardness and modulus. When fallback foods are bilayered, consisting of a nutritious core protected by a hard outer coat, it is possible to predict their failure force from the toughness and modulus of the outer coat, and the modulus of the enclosed core. These forces can be high and bite forces may be maximized in fallback food consumption. Expanding the context, the same equation for the failure force for a bilayered solid can be applied to teeth. This analysis predicts that blunt cusps and thick enamel will indeed help to sustain the integrity of teeth against contacts with these foods up to high loads

Grasping in primates: for feeding, moving and human specificities (Saisir chez les primates: se nourrir, se deplacer et les specificities humanines)

For a long time, humans (genus Homo) were thought to be the only mammalian species capable of dextrous manual grasping. However, grasping is widespread among tetrapods, and among primates, it is associated with a wide range of morphological, dietary and locomotor variation. From an evolutionary perspective, this prompts several questions: is the origin and evolution of grasping in primates derived from requirements associated primarily with feeding or primarily with locomotor behaviour? Are there grasping abilities that are unique to humans? Who made the first tool? The main purpose of this paper is to present a short overview of grasping in primates in order to open a discussion. We show that grasping strategies vary across species, depending on food properties and the substrates used. We also demonstrate that non-human primates can control individual digits, allowing them to use their hands dextrously. Finally, we discuss the challenges that arise in distinguishing anatomical features related to grasping and the debate around the first hominin tool-makers

Common Territories in Comparative and Developmental Psychology: Quest for Shared Means and Meaning in Behavioral Investigations

Comparative and developmental psychology have impacted one another for well over 100 years. Researchers have studied developmental processes of humans and nonhumans to formulate evolutionary theories and to determine the contributions of hereditary and experiential factors at ontogenetic and phylogenetic levels. We discuss current directions in comparative and developmental research that attend to micro-developmental processes and ecological contexts as sources of variability in humans and nonhumans. This research has been a segue into studies of behavior that are integrative in scope, such the family of systems theories, which cross disciplinary boundaries. We present findings from our research on instrumental manual activity in human and nonhuman primates from a systems perspective, and argue that integrative systems approaches hold promise for understanding individuals and development of behavior across species