QUESTION
Describe how genes interact with environmental factors to affect behavior.
ANSWER
Early humans had no concept of inheritance, DNA, or the translation of genetic information into morphology, physiology, or behavior. However, they intuitively understood that inheritance influences behavior. Herds and flocks of animals useful to humans were domesticated by controlling mating. Domesticated animals such as cattle, horses, and dogs behave very differently than their wild forefathers. Even though the underlying science was not understood until the Darwinian and Mendelian revolutions in the nineteenth century, selective breeding was a critical insight in human history.
We now understand that both genes and environment influence behavior, and scientists studying behavior focus on the interaction between these two factors. Genes, through their influences on morphology and physiology, create a framework within which the environment acts to shape an individual animal’s behavior. The environment can influence morphological and physiological development, and behavior develops as a result of the shape and internal workings of the animal. Genes also build the framework for learning, memory, and cognition, which are remarkable mechanisms that allow animals to acquire and store information about their surroundings for use in shaping their behavior.
Behavior and Instinct
Instinctive or hard-wired (i.e., genetically determined) behavior piqued the interest of Charles Darwin and, later, ethologists like Niko Tinbergen. Instinct implies that a behavior is carried out without thought and cannot be changed through learning. Simple behavioral patterns displayed in response to a specific stimulus or within a specific context are examples of instinctive behavior. When a light is turned on, a cockroach flees to the safety of a dark nook. Before falling asleep, a dog may circle its bedding several times, as if trampling vegetation. A rattlesnake will strike at a moving, warm object the size of a mouse. When shaping its response, the animal in none of these cases engages in learning or thought. When a species’ environment varies little from generation to generation, genetic (innate) information best determines behavior, or in communication when unambiguous messages must be sent and received.
Describe how genes interact with environmental factors to affect behavior.