Genes and Environment in Human Behavior: Sociocultural Influences and Politics

An understandable fear held by many humans is that their behavior is pre-determined by their genes. If this were the case, a person might be uncontrollably locked into bad parenting, violent behavior, or drug addiction. Most human cultures hold strong beliefs in self-determination and free will, as well as the ability of humans to separate right from wrong and to make choices about the appropriateness of their actions. Heated arguments among biologists, philosophers, religious leaders, and ethicists over the relative roles of genes and behavior in human behavior have brought no simple resolution. The evils of eugenics influence many to oppose consideration of any role for genetics in human behavior. Some biologists have been criticized for underestimating the role of thought and reasoning in human behavior, while others have been accused of ignoring the power of evolution in shaping genetically adaptive behavior. This debate is far from resolved and will continue to fuel controversy, even as more is discovered about the genetic and evolutionary bases of behavior.

Conclusion

Evolution has acted so that genes and environment act to complement each other in yielding behavioral solutions to the survival challenges faced by animals. Innate, or instinctive, responses allow animals to benefit from generations of natural selection on behavior. Learning gives animals tools to respond to local conditions and changing environments. Understanding the relative roles of genes and the environment in determining human behavior continues to create controversy. Behavior is best seen as the result of evolutionary processes that sometimes create, through genetic coding, behavioral instructions for animals and at other times create flexible mechanisms to allow animals to solve problems specific to their environment.

Ways genes and environment interact:

• Mutagens – Mutagens are pollutants in the environment that enter the body and directly change your DNA sequence. Example: The chemicals in cigarette smoke can cause cancer.
• Gene-gene interactions – Gene-gene interactions occur when pollutants in the environment do not change your DNA sequence, but rather cause a chain reaction that affects the functioning of one gene that then affects the functioning of another gene. Example: Regularly drinking way too much alcohol can cause a specific gene, TACE, not to produce enough of itsprotein. TACE protein is supposed to help the MTHFR gene make enough of its protein. Too little MTHFR protein changes the level of folate (another protein) in our blood, and low folate levels may cause depression.
• Transcription factors – Pollutants in the environment can indirectly affect the DNA sequence by altering transcription factors, which are responsible for starting the process of using genes to make proteins that are needed for different functions in the body. Example: Stress can change the amount of proteins made by genes involved in your immune system and therefore, you may get sick more easily when you’re stressed.
• Epigenetics – The environment can alter your health by affecting the proteins that turn genes on or off. Continue reading for more information onepigenetics. Example: half the genes that cause familial or inherited cancer are turned off when pollutants in the environment affect these proteins. Because they are turned off, these genes cannot suppress tumor formation or repair DNA.
• The epigenome is the primary location of gene-environment interactions and can be altered by the environment both directly and indirectly. It literally means “on top of or in addition to genetics,” or basically factors outside of the genetic sequence. Epigenetic factors (most famously histone modification and DNA methylation) can switch genes on or off and determine what proteins are transcribed. They are involved in many normal cellular processes and epigenetic changes are a natural part of human development. Some changes, however, can lead to disease. Some of these abnormal changes can lead to diseases such as:
• Cancer
• Mental retardation
• Neurodevelopmental disorders
• Cardiovascular diseases
• Type-2 diabetes
• Obesity
• Infertility

Some environmental exposures and dietary factors can lead to abnormal changes in epigenetic pathways. Because epigenetic changes are subtle and cumulative, it is difficult to know the true causal relationship between epigenetics and the environment. Some factors that can lead to epigenetic changes include –

• Heavy metals, such as cadmium
• Vinclozolin, a widely used pesticide
• Folate and methionine deficiencies
• Cigarette smoke

The presence of drugs or chemicals in an organism’s environment can also influence gene expression in the organism.

Temperature and light are external environmental factors that may influence gene expression in certain organisms.

Environmental Influences on Gene Expression