Brain, behavior and genetics

Nicolas Wade’s controversial book documenting the genetics of race is most often attacked because of the connections he tries to make between genetic differences and behavioral differences between the races. He has been publicly called out by scientists for this very point.

But there are a few cases where genetic changes clearly influence human behavior. Michael White documents a few for Pacific Standard magazine. Tourette syndrome, for instance, is caused when one enzyme, histidine decarboxylase, fails to do its job of cleaving a chemical group from the neurotransmitter. People with Tourette syndrome have issues controlling inappropriate behavior like cursing.

Anther example is the language-crucial FoxP2 gene. Interestingly, all mammals have this gene. But only humans and Neanderthals have or had two mutations which are crucial to developing language. Even chimps and other apes don’t share it. One British family was found to have FoxP2 mutations by doctors who they came to for help with language impairment:

This small mutation caused an amino acid swap, replacing an arginine with a histidine in a part of the protein called helix 3. This swap alters the function of FoxP2, hampering its ability to bind DNA and control a gene that helps form contact points between neurons in the brain. The ability to use and understand language is severely damaged by this single amino acid switch.

There are more, White lists, that likely work in concert with other genes to control disorders like autism, anorexia and obsessive compulsive disorder. These are likely not the only cause of the disease, as in the case of histidine decarboxylase and Tourette syndrome or FoxP2 and language development, but they are at lease one mechanism by which a condition can be acquired.

And, we know from recent reports just how incredibly complicated those biological systems controlling neurological conditions can be. Take schizophrenia, long the subject of genetic analysis, which is just now uncovering some genetic targets of the disease.

Regardless of where the science now lies, we know that biology controls behavior. Our actions and thoughts aren’t magic, they rely on the biochemistry of neurotransmitters and nerve signals. They have physical substrates that are controlled by our genes, says White:

Will we ever be able to reason from the behavior of proteins and cells to the behavior of human beings? This can be a dangerous question because it is hard to study and easy to speculate. But it’s a crucial one because we won’t fully understand our most human traits—personality, behavior, language—without making sense of the molecules behind them.

Meredith Knight is a blogger for Genetic Literacy Project and a freelance science and health writer in Austin, Texas. Follow her @meremereknight.

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1 thought on “Brain, behavior and genetics”

  1. Nice piece Meredith.
    From our other GLP discussion on this:

    The differences in each of us are due to differences in our genes. There isn’t a ‘tabula rasa’ where there’s a homogenous template that makes us all ‘human,’ and then our genetic code is supplemented on top of that; Each of our features is specified by our genes — so that each difference in behavior, physical stature, etc. is coded in our genes. What I meant by the last line was that people don’t need to get emotional over this divide – it’s simply that we’re all different, and these differences are caused by genetic differences.

    It’s nature AND nurture (where nurture means environmental factors, such as nutritional status). But some of this is also recursively back to genetics, because of epigenetic changes based on environmental conditions faced by each individual.
    What makes this a complicated research topic is that there are so many multifactorial issues (environment, weather, access to nutrition, healthcare, education, size of sibling group, etc., etc., etc.) that certain factor effects, like environment, can overwhelm a particularly small effect made by individual genetic changes. But we’re all a product of genetics plus environment. There was a time when the XYY research was going to be THE answer to criminal recidivism, but that didn’t resolve it either.
    Check out Bates et al. (2012) in Journal of Personality. As the study lead referred to the results:
    “Previously, the role of family and the environment around the home often dominated people’s ideas about what affected psychological wellbeing. However, this work highlights a much more powerful influence from genetics.”

    cf.
    https://geneticliteracyproject.org/2014/03/28/genes-indicted-as-tool-for-new-racism/

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