The Question of the Extent of Biological Influence

By: Robert L. White

             The question of the extent of biological influence (genetics) upon behavior is one of hot debate.  Public outcries against statements linking the two are common. In the past, evidence supporting a genetic component in behavior has been twisted by governments and used to support atrocities. Yet, still the subject intrigues us. Current research aimed at mapping the physical location in the brain for control of given emotions and behavior patterns show a definite link between anatomy and behavior. Case studies of humans with brain damage show permanent changes in behavior. If emotions and behavior are controlled by physical locations in the brain, one cannot deny a genetic influence (it is, after all, genetics that determines the structure of those locations). Still, most people have difficulty accepting any evidence linking genetics and behavior, repelled, perhaps by the suggestion of determinism. And so we come to the heart of the matter. Does a genetic element in behavior deny free will? That is the real question. A complete denial of free will undermines much of what our culture is built upon. The basic ideas of reciprocity and justice depend of the free will of the participants. A gift from someone who has no choice has little value. Likewise, punishing someone for a deed when the offender could not have done otherwise is impotent and futile, let alone unethical.

            The real dilemma is whether admitting a genetic link with behavior and emotion denies free will. Is there some compromise, some middle ground where the deterministic genetics can stand with the perceived chaos of unpredictable choice that seems to be our nature? To answer this question we must first examine the genetics, the physical mechanism by which our anatomy and physiology are made. Then, we need to look at the evidence regarding the extent to which physical location and behavioral pattern and specific emotion are interwoven. Finally, we must examine the question of free will versus determinism itself, to see what light can be shed on the issue from the philosophical side.

            Let us start with the central dogma of molecular biology; DNA codes for RNA which Codes for proteins. Most people in the western world today have at least some degree of familiarity with the idea, if not the exact phrase. But what does it mean? As simply as possible, it means that the blueprint for every physical detail of any person (let alone all other living things as well) is written in a language of four letters (A,T,C & G). These stand for the chemicals that make up DNA. These four letters (chemicals) are arranged into three letter words. Long chains of three letter words are the chromosomes that get so much attention in the media from genetic disorders such as Turner’s and Down’s syndromes. The entire blueprint (for the whole organism) is located in the on the chromosomes in the center, called the nucleus, of every cell in the organism. The central dogma is a shorthand way of representing the process by which the blueprint gets turned into a living organism. Those three letter words that spell out the specifics of the blueprint get changed into three letter words in the language of RNA. This process (the first half of our dogma) is called transcription.

Enzymes that copy the blueprint into RNA language constantly scan the DNA for a specific combination of letters, AUG, which signals those enzymes to begin their work. These enzymes then chemically match the individual bases (represented by the letters A,T,C & G), of the RNA to the DNA. The RNA units are then linked up like a long chain, a sort of mirror image of the DNA from which they were copied. It is at this point that the message leaves the nucleus and moves into the main body of the cell, all the while guided by enzymes.

From the nucleus, the RNA (now called mRNA for “messenger” RNA) travels down a sort of cellular highway called the Rough E.R. . At the end of the Rough E.R. , the mRNA meets up with a structure known as a Ribosome. The ribosome is a combination of enzymes and a special kind of RNA. The job of the ribosome is the focus of the second half of the central dogma, the process of changing instruction written in RNA language into a working protein.

This process, called translation (after the idea that it is taking a message from one language (RNA) and copying it into another language (protein)), happens at the ribosome. The ribosome works by “reading” the three letter words of the mRNA. Each three letter word must match exactly the complimentary three letter word on yet another kind of RNA. This tRNA, for transfer RNA has the job of bringing a specific amino acid to the ribosome for inclusion in a growing chain of amino acids called a protein.

If you did the math, you would find that there are 64 possible combinations of three letter words from a four-letter alphabet. Thus, there are 64 possible combinations of our original A’s, T’s, C’s and G’s. The same is true of RNA (except that RNA has no T’s; it uses another base instead: the U).  However, all the proteins we have are made up of only 20 different amino acids arranged into long chains. What biologists refer to as “redundancy” actually occurs in the tRNA. There are 61 different tRNA’s. Some of them carry the same amino acid as other tRNA’s. This keeps the process from having ambiguity as a result of having a mRNA word that does not mean anything, or has more than one meaning. The result is a system that does not require any sort of sentient judgement. Each three letter DNA word can only mean one three letter RNA word which itself can only mean one amino acid. (If you are still doing the math, and wonder where the 3 missing three letter words went (64 possible three letter RNA combinations minus 61 tRNA’s). you are paying more attention than I had hoped! They are used as signals for the process to stop, thus do not need tRNA’s since no more amino acids are needed).

The focus of this whole process is the proteins. Proteins do everything. All cellular processes are in some way moderated if not directly carried out by proteins. They are the construction workers, the food producers, the messengers and the supervisors of every aspect of the cellular workings. From the construction of the very nucleus that protects the DNA to the cell’s ability to function and interact with the rest of the cells in the entire organism, as well as the surrounding environment, proteins do it all. Remember: all of the steps of the process described as the central dogma of biology are mediated by enzymes. Enzymes are just one of the many types of proteins.

So it is that we find ourselves speaking of “hormones” when referring to the actions of teenagers. PMS has been theorized as being the result of hormonal imbalances during menstruation. Grandmothers present diagnosis of the sex of a future child based upon the changes in the skin of the mother. (The folklore has it that hormones of a male child cause the female mother to show signs of acne!). We look now toward children of alcoholics for increased likelihood of alcoholism and violence all the while couching the idea of genetics behind such phrases as “inherited susceptibility” in science and “like father, like son” in folklore.

We seems to intuitively understand the relationship between mother (or father) and child without realizing (and even rejecting) the logical extension of our acceptance of both the intuition and the science; there must be some degree of connection between inheritance and behavior).