Combined change of behavioral traits for domestication and gene-networks in mice selectively bred for active tameness

Tameness is a major element of animal domestication and involves two components: motivation to approach humans (active tameness) and reluctance to avoid humans (passive tameness). To understand the behavioral and genetic mechanisms of active tameness in mice, we had previously conducted selective breeding for long durations of contact and heading toward human hands in an active tameness test using a wild-derived heterogeneous stock. Although the study showed a significant increase in contacting and heading with the 12th generation of breeding, the effect on other behavioral indices related to tameness and change of gene expression levels underlying selective breeding was unclear. Here, we analyzed nine tameness-related traits at a later stage of selective breeding and analyzed how gene expression levels were changed by the selective breeding. We found that five traits, including contacting and heading, showed behavioral change in the selective groups comparing to the control through the generations. Furthermore, we conducted cluster analyses to evaluate the relationships among the nine traits and found that contacting and heading combined in an independent cluster in the selected groups, but not in the control groups. RNA-Seq of hippocampal tissue revealed differential expression of 136 genes between the selection and control groups, while the pathway analysis identified the networks associated with these genes. These results suggest that active tameness was hidden in the control groups but became apparent in the selected populations by selective breeding, potentially driven by changes in gene expression networks.

Human Social Evolution: Self-Domestication or Self-Control?

The self-domestication hypothesis suggests that, like mammalian domesticates, humans have gone through a process of selection against aggression - a process that in the case of humans was self-induced. Here, we extend previous proposals and suggest that what underlies human social evolution is selection for socially mediated emotional control and plasticity. In the first part of the paper we highlight general features of human social evolution, which, we argue, is more similar to that of other social mammals than to that of mammalian domesticates and is therefore incompatible with the notion of human self-domestication. In the second part, we discuss the unique aspects of human evolution and propose that emotional control and social motivation in humans evolved during two major, partially overlapping stages. The first stage, which followed the emergence of mimetic communication, the beginnings of musical engagement, and mimesis-related cognition, required socially mediated emotional plasticity and was accompanied by new social emotions. The second stage followed the emergence of language, when individuals began to instruct the imagination of their interlocutors, and to rely even more extensively on emotional plasticity and culturally learned emotional control. This account further illustrates the significant differences between humans and domesticates, thus challenging the notion of human self-domestication.

The crayfish model (Orconectes rusticus), epigenetics and drug addiction research

Fundamental signs of epigenetic effects are variations in the expression of genes or phenotypic traits among isogenic mates. Therefore, genetically identical animals are in high demand for epigenetic research. There are many genetically identical animals, including natural parthenogens and inbred laboratory lineages or clones. However, most parthenogenetic animal taxa are very small in combined epigenetic and drug addiction research. Orconectes rusticus has a unique phylogenetic position, with 2-3 years of life span, which undergoes metamorphosis that creates developmental stages with distinctly different morphologies, unique lifestyles, and broad behavioral traits, even among isogenic mates reared in the same environment offer novel inroads for epigenetics studies. Moreover, the establishment of crayfish as a novel system for drug addiction with evidence of an automated, operant self-administration and conditioned-reward, withdrawal, reinstatement of the conditioned drug-induced reward sets the stage to investigate epigenetic mechanisms of drug addiction. We discuss behavioral, pharmacological and molecular findings from laboratory studies that document a broad spectrum of molecular and, behavioral evidence including potential hypotheses that can be tested with the crayfish model for epigenetic study in drug addiction research.

Physiological pathways to rapid prosocial evolution

Dogs (Canis lupus familiaris) descend from wolves (Canis lupus) sharing the same ecological niche of cooperative hunters, as humans. Initially, humans and wolves were competitors starting interspecific communication in order to avoid risk of injury. The evolutionary continuity of mammalian brains enabled interspecific prosocial contacts between both of them, which reduced stress, and enabled behavioral cultures leading to genetic isolation of those wolves. Dogs are the first domesticated animal living together with humans for about 25,000 years. Domestication means decreased aggression and flight distance toward humans, thus changes in the stress axis are crucial. The hypothesis of Active Social Domestication considers genetic selection as a necessary prediction but not a sufficient explanation of dog domestication. In addition, dog domestication is suggested to be an epigenetic disclosure. Due to changed stress activity, epigenetic mechanisms affect cerebral receptor activity and regulate transposon expressions, thus shaping brain function and behavior. Interspecific prosocial contacts initiated via serotonin release an enzymatic cascade enhancing, epigeneti-cally, the glucocorticoid negative feedback loop. Reduced chronic stress improved social learning capability and inhibitory control. Over time, those wolves could integrate themselves into human social structures, thus becoming dogs. In analogy, human mental skills, such as creating art and culture, might have also improved during the Upper Paleolithic.