My blog entries have been sporadic recently, because we have had recurring storms that have closed down educational institutions. (I do not have internet connections at my house.) I was expecting that I would get back to my series of essays based on my new book, Life of Earth. But during the most recent snow days, I happened to start reading a book by my fellow Prometheus Books author, Barbara Oakley. The book is Evil Genes: Why Rome Fell, Hitler Rose, Enron Failed, and My Sister Stole My Mother’s Boyfriend. How could you not want to read a book with that title?
I found myself frequently lost in the mass of information, but that is, I think, the nature of the subject. Maybe nobody could make it fully comprehensible. And the author’s stories, of historical figures and personal experiences, drew me in anyway.
At first, one would think the book was intended as an argument against the Skinnerian blank-slate theory. (Last year I read Skinner’s Walden Two as one of my rare ventures into fantasy.) But very few people take that theory seriously anymore, and Oakley’s purpose is not to tell us that but to tell us how genes affect human behavior.
First, there are no genes for behavior patterns, but there are genes for inclinations such as impulsivity and anxiety. There are many examples interspersed through the book, but I will mention just one. Serotonin is a chemical that carries messages in the brain. After it has delivered its message, it has to be re-absorbed by the neuron that released it. This reuptake is the business of the SERT (serotonin transporter) protein. If serotonin lingers in the spaces between the brain cells, anxiety can result. A word about genes: they contain stretches of non-coding DNA, such as tandem repeats, which are not transcribed into the protein. Just junk, you say? Read on. The SERT gene has two forms (alleles), the short form (with 14 tandem repeats) and the long form (with 16 tandem repeats). Aside from these seemingly meaningless insertions, the alleles are identical. The short allele results in the production of less SERT, and therefore contributes to anxiety. I hope I got that right.
Second, differences in brain structures influence behavior patterns as well. Psychopaths, for example, often have a defective corpus callosum, the part of the brain that connects the left and right sides. They also have a smaller amygdala, an almond-shaped structure in the middle of the brain. Perhaps these people need more excitement in order to feel normal, and have less fear, both of which contribute to a dampening of conscience. A dysfunction of the right orbital cortex (just behind the eye) also makes it difficult for a person to form a conscience. The brain structure differences between one person and another are influenced by which alleles the person inherits.
Third, brain chemicals and structures both influence brain circuitry. This circuitry is what determines behavior. One example is that the amygdala sends fear signals to dampen the cingulate cortex, but this communication is inhibited if the person has one or two copies of the short version of the SERT gene. Indeed, people with the short allele have smaller amygdalae and cingulate cortices. Again, I hope I got that right.
It gets even more complicated. The behavioral abnormalities recognized by psychologists often overlap: each disorder has some characteristics of the others. This may be because each behavior pattern is influenced by many parts of the brain and many brain chemicals. This is one reason why people who have the “same” disorder differ from one another so much. But, based on the three points above, it is clear that differences in genes result in differences in behavior, all other things being equal.
Of course, all other things are never equal. Environment is important too. Nearly every trait, and perhaps every behavioral trait, is both genetic and environmental, never one or the other. Part of this is the prenatal and childhood environment. Time and again, researchers have found that people with the same physical brain problem may develop more or less normally if they had good childhoods, but develop behavioral problems if they had abusive childhoods. I say more or less, because the normal people with brain problems still have to struggle a little—but they are generally successful. Environment is why some people with brain problems become clinically dysfunctional and some do not.
Of course, there is even more, something that is largely absent from Oakley’s book. We can influence our own habits of thought, to a certain degree. New brain cells develop in our brains, but too few to be of much use. However, the old cells keep destroying and rebuilding connections. Frequently-used connections, therefore frequently-used behavior patterns, are reinforced. This is not enough to wholly compensate for chemical or large-scale structural problems, but it helps.
Genes create our brains; environments create our brains; and we create our own brains.
Genes make us capable of evil behavior, but also good behavior. Sometimes pathologically good behavior. Everyone’s favorite mutants are the people with Williams syndrome, traced to defects on chromosome 7. These people are completely trusting of strangers; they are super-altruists. I’ve never knowingly met one, but my impression is that they are the sweetest people you could know, sort of like straight out of the pre-pome Garden of Eden. It turns out that they stress out about everything except strangers, but hey, nobody’s perfect.
The point for this evolution blog is that there is a lot here for evolution to work on, in both trusting and evil directions. Scientists would say there is a lot of heritability for good and evil behavior patterns. Evolution can, of course, work on the alleles, for which every human population has plenty of variation. Evolution can also work on the culture. The only thing it cannot work on is you as an individual. But you as an individual can work on evolution—that is, at least you can contribute to cultural evolution.
More on this next time. Meanwhile, I just note that differences in behavior patterns appear to be due to genes, brains, environment, and habits, not to spirits, human or Holy.