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Brains’ Social Network Formula Dates Back Hundreds of Millions of Years

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Newts aren’t doing a lot of Facebook friending, and last time I checked, the cormorant had not updated its relationship status. But a new neural analysis suggests that our social networking tendencies most likely have their neural roots in some of our early vertebrate ancestors. The findings were published online May 31 in Science.

“There is ancient circuitry that appears to be involved in social behavior across all vertebrates,” Hans Hofmann, an associate professor of integrative biology at the University of Texas at Austin and co-author of the new study, said in a prepared statement. Judging from the evolutionary family tree, Hofman observes, these conserved neural clusters originated at least 450 million years ago.

Hofmann and graduate student researcher Lauren O’Connell examined two parts of vertebrate brains: the so-called “social behavior network,” which also includes hormones for social and sexual behavior, and the “mesolimbic reward system,” which is involved in dopamine signaling that activates when we engage in pleasurable behavior. Together these two areas make up the social decision-making network, which helps humans, rainbow trout and wild boars know when to flirt or fight or form a posse. They found impressive similarities in the brains of all 88 vertebrates they studied, which included mammals, reptiles, birds, amphibians and teleost fish.

“In these key brain regions, we found remarkable conservation of gene activity across species,” Hofmann said. Even though the general biological and behavioral differences between the newt and your next-door neighbor are (likely) pretty vast—making attempts to draw connections between neural structures and daily actions tricky—the genetic similarities should start to help.

The next step will be examining neural patterns at an even finer-grained scale to study the underpinnings of complex social behavior. Said Hoffman: “Now we have a framework with which we can ask whether there are molecular universals associated with social behaviors.” They also noticed, however, that the locations of some key receptors and molecules were different among the groups, which suggests adaptation to specific needs in the intervening millions of years.

The researchers did not look into the brains of invertebrates, many of which are quite evolutionarily complex and move in semi-social groups—such as squid.

But for now, “On a basic level, this tells us something about where we came from,” Hofmann said.

Now, whether you have enough backbone to take charge of your own social network, that’s up to you.

Katherine Harmon Courage About the Author: Katherine Harmon Courage is a freelance writer and contributing editor for Scientific American. Her book Octopus! The Most Mysterious Creature In the Sea is out now from Penguin/Current. Follow on Twitter @KHCourage.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. jvkohl 9:25 am 06/1/2012

    The molecular universals of cause and effect are exemplified in the adaptive evolution from yeasts of the ligand-receptor binding exemplified across species by the conservation of gonadotropin releasing hormone (GnRH) and diversification of its receptor.

    Model organisms like the threespine stickleback make clear the involvement of nutrient chemical molecules in ecological niche construction. The honeybee invertebrate model organism makes clear the involvement of the nutrient dependent ecological niche in construction of the pheromone-dependent molecular biology of social niches.

    Invertebrate and vertebrate models collectively attest to the common molecular mechanisms of adaptively evolved social decision-making networks. In mammals, the hypothalamic neurogenic niche (probably located in the medial preoptic area of the anterior hypothalamus) responds to nutrients to enable fertility and responds to pheromones to enable sexual reproduction that has adaptively evolved via effects on cell memory and neuronal systems learning and memory from its origins in brewer’s yeast.

    Never before has there been such a clear representation of cause and effect across species from microbes to man, where nutrient chemicals calibrate the intracellular signaling and their metabolism to pheromones standardizes and controls the stochastic gene expression required for reproduction.

    Nutrient chemical and pheromone-dependent gene expression enables adaptive evolution of the brain via direct effects on the hypothalamic neurogenic niche and ensures that our ability to acquire nutrient chemicals is the first priority for reproduction via appropriate social behaviors, as it is in every species. For example, microbes — with only their intracellular memory — eat the DNA of heterospecifics but not conspecifics, which indicates more social sense than what some people today are capable of recognizing in the design of biology (the evolved gene, cell, tissue, organ, organ system pathway that directly links sensory input to the mammalian neuroendocrine system and the hormones responsible for our behavior, which activates the same ‘organized’ pathway).

    Link to this

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