Sociomolecularbiology

Society affects gene expression and development, and genes contribute to social traits and behavior.

Is it any news that we are biological beings? That all aspects of our being, from toenails to theology, are biologically based? That was the premise of sociobiology, the science of the behavior and evolution of social organisms. Of which we are one. Unfortunately, the smell of eugenics was still too strong in the political atmosphere to allow thinking about how our genes affect our behavior, so that splash by E.O. Wilson died down and the science went on by other names.

That work has found, among other things, many connections between our psychology and our physiology. It should be no surprise that we are profoundly affected, to the point of suicide and other forms of death, by information that first arrives to our brains. Our immune systems are sensitive to social state, as are digestion, mood, activity, etc. Hypertension is one of many long-term consequences of stress, for example. This close relationship leads to to idea that we might be able to judge happiness by objective measures, rather than exclusively by self-report. And that would open up new vistas in morality, particularly morality vis-a-vis other species.

But it goes the other way as well, as our social capacities are based on biology. Psychological traits of great complexity can run in families, and scientists are only starting to gain glimpses of genetic alterations that cause such traits and their variation. The very ability to be flexible, to learn and adapt, is itself obviously of genetic origin. The question, typically, is how much people differ in significant social traits and how much we should care about that. We pride ourselves on meritocratic systems of education, business, and government that weed, select, and reward those who are gifted, who also align with and master the social system. But are we just rewarding something that the persons themselves had little to do with, just as criminals typically have little responsibility for their genetic or social deprivations, or actors for their looks? We may be, but reward we must, as a sociological necessity, if we want societies to benefit from good rather than bad talents.

Is it also an evolutionary necessity? Should those who succeed in the existing social system be rewarded with more reproduction? Typically we do not and should not have sufficient confidence in the universality or durability of our social system to make that case in its most brutal, eugenic sense. However, we should not be blind to the genetic underpinnings of social success and all its consequences. For example, the trend toward intellectual atheism that is so fervently touted in other areas of this blog fights a rate-dependent battle against the higher reproductive success as well as intellectual insularity of religious populations. What is the deconversion rate compared to the biological and ideological reproduction rate? Is religiosity a positive trait for humans? How much to we care about our evolutionary trajectory, a path we are on whether we are conscious of it or not?

Anyhow, as an example of the genetic implications of sociality, a recent paper described a gross increase in genetic complexity that accompanied the social evolution of bees. They found a measurable correlation between social complexity and gene regulatory complexity, which is a step in addressing the question of the interrelation of genes and behavior, in general.

Bees come in many social levels, from solitary to "eusocial", a term the E. O. Wilson made up to describe animals that are not  just polite and social as we and many other animals are, but behave as super-organisms, with genetically determined castes with division of labor, and restriction of reproduction to a small subset of those castes. The members of such a collective have no independent existence, die when the hive dies, and are seen by evolution as a group that has group-level traits that are extensively selected for.

Phylogenetic tree of the species considered. Solitary bees are marked in blue, simple sociality in green, more advanced sociality in yellow, and full-blown eusociality on red. 

The researchers basically lined up lot of genomes, from various levels of social organization among the bees, and looked especially at promoter regions, where the primary control over gene expression happens. They found a striking increase in complexity, which is to say number of binding sites for regulatory proteins, all over the genomes of the more social species. Indeed there was a 10-to-1 bias of genes that gained promoter binding sites over those that lost sites in the more social species. This is a dramatic effect, and makes sense in terms of the "mode-switches" required on a genetic level to create castes with separate developmental and behavioral traits out of one ancestral species.

Bias found among orthologous bee genes (that is, the same between each species) between those that gained promoter regulatory sites in more social species (blue) and those that lost them (red). The X axis is not genes, but the individual regulatory proteins whose DNA-binding sites were identified.

They also found, interestingly, that the particular genes involved in these increases were not the same in different social insect lineages. They took different genetic / evolutionary routes to eusociality in detail, even though they ended up with similar properties. So this is a kind of convergent evolution that shows that group selection and the sociality it selects for did not just arise multiple times in life's history out of some kind of molecular happenstance, but is an optimal ecological solution that attracts quite a bit of selection, as we can tell by the dominance of social species, both in the insect world and in our own.

Overlap among the various social lineages of which genes showed rapid, positive evolutionary selection. The result is that there is very little overlap, indicating that there are many ways to skin the social cat.

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