Genes are amazing things. But over the past few decades, the power we've given them has spiraled a little out of control. This led to the rise of biological (or genetic) determinism. This view holds that our biological makeup (as opposed to cultural, environmental, or personal decisions) is the primary determinant of our behavior.
There is now a "warrior gene" legal strategy for criminal defenders to defend people accused of violent crimes. (A cartoon depicts a lawyer stating his client's defense in court: "Your Excellency, he is not guilty because of genetic determinism.") At least one company will test your genome for so-called "unfaithful genes." You can submit a saliva sample to see if you (or your potential partner) have a variant of this gene that could potentially lead to a relationship**. All for a low price of $149! This company can also help you discover if thrill-seeking and risk-taking (the "wanderlust gene") are present in your DNA.
But as we learn more about genetics, the idea that genes are the controllers of our behavior becomes less and less convincing. As one scientist (at least a biologist) wrote:
Many critics expect our genetic gifts to accomplish feats that we can...... can'tThe statement that 'understanding the genetic roots of your personality will help you find yourself and get along better with others' is, frankly, absurd at today's level of knowledge. ”
When we talk about this topic, one key mistake we often make is this: genes don't code for traits. They certainly don't encode behavioral traits (such as kindness). But in the vast majority of cases, genes don't even code for physical traits (like hair color). Some of our misconceptions about this come from the Mendelian genetics curriculum in elementary school. You may remember Gregor Mendel's pea plant and the concept of dominant and recessive traits. In this basic lesson, crossing two pea plants with smooth peas (dominant trait) results in three-quarters of the offspring plants with smooth peas (dominant trait) and one-quarter with wrinkled peas (recessive trait).
But, as we have already discovered, traits inherited in a simple Mendelian way are the exception, not the rule. In humans, they are very rare. Human examples of Mendelian inheritance come from diseases (sickle cell anemia, cystic fibrosis, and Huntington's disease, to name a few) rather than normal physiology. In humans, normal traits that follow the Mendelian pattern of inheritance do not appear to be present. Even traits that we once thought were inherited in this simple pattern, such as eye color, are now understood to be much more complex.
Genes actually encode proteins. Proteins are the molecular machines that build and keep our bodies running smoothly. Some proteins that fight infections are called antibodies. Others help provide structure or allow muscle elasticity (titin). There are also those that transmit information through the bloodstream, known as hormones. How many different proteins are there in humans? No one knows for sure. Some experts estimate that our genes make hundreds of thousands to billions of different types of proteins.
As our understanding of genetics has deepened, so has support for genetic determinism. We've learned that genes themselves aren't really the best people. They are regulated (on or off) by transcription factors. In turn, these transcription factors – which is the death knell of genetic determinism – are regulated by the environment. As neuroendocrinologist Robert Sapolsky put it, "It doesn't make sense to ask about the role of genes, just ask about what they do in a particular context." What does Sapolsky mean by "environment"? It can be an intracellular environment, an extracellular environment, or an extracorporeal environment.
Most scientists believe that genes have some influence on our traits – both behavioral and physical – but the way this affects them is very complex and very indirect. In humans, there are few known examples of genetic variants that have a quantitative link to behavioral responses. Even if we do find genetic variants that can be quantitatively linked to a certain behavior, these estimates are very imprecise. Genes do shape and influence our behavior, but they don't determine our behavior. In other words, there are no genes for selfishness or aggression; Similarly, there are no genes for kindness or cooperation. Obviously, genes play a role in our behavior. But the reality of the human psyche is increasingly seen as far removed from some kind of genetic behavioral determinism.