More on genes and personality

I think the first rule of genetics has got to be, if you think you understand it, you're overlooking something.

When I learned my way around Microsoft Access, I eventually had to delve into writing modules and other code in a database I was repairing. My first programming language was Fortran, which introduced me to the wonders of spaghetti code.  (Program flow runs line by line, until it reaches code which can send it anywhere else in the program.   Tracing this flow is like following a single strand in a bowl of spaghetti.)  Pascal and similar languages introduced me to structure, and writing modules -- paragraphs, if you will -- with no branching in or out except at the designated entry and exit pointsl.  This, I call "ravioli code".  Programming in Access (actually, in Visual Basic for Access) was a process I describe as like programming a bucket of marbles.  You have a bunch of little pieces, any one of which can trigger something in any other piece, or more than one.

As people study genetics, it's beginning to seem that genetic programming works the same way as some of our most sophisticated computer programs.

 

Him Manzi at The Corner discusses the genetics of personality:

Media outlets will often speak loosely of things such as a "happiness gene," a "gay gene," or a "smart gene." The state-of-the-art method for finding such a link is something called a "genome-wide association study" (GWAS). In a GWAS, scientists use blood or saliva samples to sequence the DNA for a group of several thousand people who exhibit a trait or behavior of interest (the "case group"), and for a second group of several thousand who do not exhibit the trait or behavior (the "control group"). Scientists then look for genetic differences between the two groups.

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Sometimes, however, the behavior or trait is caused by several interacting genes — so that, for example, Gene 1 has some effect only if Gene 2 has a special structure. This is called "epistatic interaction," and can involve a large number of genes.

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...the GWAS technique hits structural limits when applied to conditions that involve epistatic interactions among lots of genes. Mental activity is now widely believed by scientists to depend on many genes (though mental illnesses such as schizophrenia or bipolar disorder may turn out to be partial exceptions). A person has about 20,000 genes, of which more than 5,000 are believed to play some role in regulating brain function. Consider a simplified case in which some personality characteristic — aggressiveness, for example — is regulated by 100 genes, each of which can have two possible states ("on" or "off"). The combinatorial math is daunting: There are more than a trillion trillion possible combinations of these gene states. Thus we could sequence the DNA of all 6.7 billion human beings and still not know which genes are responsible for aggressiveness.

His conclusion:

The claims of causality that arise from such studies should accordingly be treated with the appropriately intense skepticism that we apply to sociological or econometric studies. In the middle of the 20th century, Friedrich Hayek and the libertarians he inspired faced those who asserted that that an economy could be successfully planned. The libertarian position was not that such planning could be proved impossible in theory, but that we lacked sufficient information and processing power to accomplish it. The world of economic interaction is so complex that it overwhelms our ability to render it predictable; hence the need for markets to set prices. This is the same analytical problem we face when trying to predict a mental state that depends upon a large number of genes. It is unclear whether we will ever understand how this complicated machinery and its interactions with the environment come together to create characteristics of mind. It is certain, however, that we do not have such an understanding now, and that we won't know such a project is achievable until we achieve it.