Comparative genomics and the roots of human behavior

Reflections on the Role of Differentiation Processes in Forming Behavioral Phenotypes: Can These Processes Replace the Concepts of Plastic Phenotype and Reversible Plastic Phenotype?

This essay presents two lines of argument to suggest that the extension into adulthood of specific phenotypic differentiation processes, typical of early development, is fundamental to the evolution of cognition. The first of these two lines of argument is organized in three steps. The first step reviews various studies of human development, highlighting that it has slowed down throughout evolution compared to that of great apes. The second step explores the relationship between this slowed development and human cognition. The third step discusses evolutionary comparative analyses that show a correlation between the evolution of cognitive processes and developmental changes. The second line of argument examines concepts of phenotype. First, the concepts of phenotype are reviewed in correspondence to the two meanings of the word plasticity (i.e., as the ability to alternate or as the ability to shape), and it is concluded that all phenotypes -rigid, plastic, and reversible-fit the meaning of shaping. It is proposed that a phenotypical process can be seen as a continuous series of functional differentiations that occur at different times during the life of the organism and at different contextual points, both inside and outside the organism. Finally, a brief recapitulation is presented that is focused on supporting the formation of behavioral phenotypes as a sequence of differentiation processes shaping the environmental interactions from the most general to the most particular.

Gene regulation supporting sociality shared across lineages and variation in complexity

Across evolutionary lineages, insects vary in social complexity, from those that exhibit extended parental care to those with elaborate divisions of labor. Here, we synthesize the sociogenomic resources from hundreds of species to describe common gene regulatory mechanisms in insects that regulate social organization across phylogeny and levels of social complexity. Different social phenotypes expressed by insects can be linked to the organization of co-expressing gene networks and features of the epigenetic landscape. Insect sociality also stems from processes like the emergence of parental care and the decoupling of ancestral genetic programs. One underexplored avenue is how variation in a group's social environment affects the gene expression of individuals. Additionally, an experimental reduction of gene expression would demonstrate how the activity of specific genes contributes to insect social phenotypes. While tissue specificity provides greater localization of the gene expression underlying social complexity, emerging transcriptomic analysis of insect brains at the cellular level provides even greater resolution to understand the molecular basis of social insect evolution.

The genomic case against genetic determinism

Animal studies reveal that the molecular wiring of the brain can be altered by heredity, the environment, and their interaction. A deeper molecular understanding of these interactions could be a potent antidote to societal concerns of genetic determinism for human behavior, but this requires a paradigm that extends beyond traditional genome-wide association study (GWAS).