The Science of Existence – The Genetics of Behavior

The Genetics of Behavior

“Almost all aspects of life are engineered at the molecular level.” ~ Francis Crick

Nature versus nurture is a long-standing debate about the degree to which behaviors are biologically bound as opposed to learned. That autonomic functions and reflexes are genetically encoded has never been controversial. The debate centers on behaviors from conscious decisions which may involve planning.

The crux is of cause versus correlation. Does behavior shape biology, or vice versa (causality)? Otherwise, do behavior patterns and biochemistry coincide (correlation)?

The epigenetic answer is “yes” to both cause and correlation. Behaviors invoke epigenetic changes. Genetic activity prompts behavioral modification. And behavioral and genetic dynamics go together as self-reinforcing.

An animal’s diet has epigenetic effects. Conversely, epigenetic changes may occur that shift dietary preferences. One may reinforce the other. This applies to a wide spectrum of seemingly complex behaviors, from foraging to mating and parenting.

Behaviors arise from a suite of traits. All traits are biologically based.

“The relations among genes, the brain, and social behavior have complex entanglements across several different time scales, ranging from organismal development and physiology all the way to evolutionary time. Genes do not specify behavior directly, but rather encode molecular products that build and govern the functioning of the brain through which behavior is expressed.” ~ American biologists Gene Robinson, Russell Fernald, & English psychologist David Clayton

Life experiences impress cells epigenetically. They also do so genetically.

Immediate early genes are certain genes which are instantly activated in response to cellular stimuli. Immediate early genes play important roles in behaviors, learning, memory, immune system activity, and many other bodily functions.

The emotional impacts of life are encoded genetically. Conversely, routine patterns of behavior and thought are genetic expressions.

Experiences and behaviors form a self-reinforcing cycle. Biological programming parameterizes future behaviors into predictable patterns; what is called one’s character.

“Character is simply habit long continued.” ~ Greek essayist Plutarch

As epigenetic effects are transferred generationally, and strongly set during early development, nurture is nature and vice versa. In that animals are creatures of habit, breaking a behavior pattern seems to be going against the genetic grain. But then, strength of will is also in one’s nature.

 Mice Digs

Rodent burrows are a product of planning, which involves choice of location based upon soil type, and design, including number of tunnels, width, length, and usage. Oldfield mice and deer mice both dig tunnels, but their burrows are different.

Oldfield mice consistently dig a burrow with a long entrance tunnel, along with a 2nd tunnel that stops short of the surface. The 2nd tunnel allows the mice to escape predators. In contrast, deer mice burrows are shallow and lack an escape route.

Crossbreeding between these mice resulted in a variety of different tunneling patterns and revealed the genes behind the burrows. Also unearthed was the unsurprising revelation that complex burrowing in mice evolved incrementally and piecemeal, by combining genic modules responsible for simpler digging behaviors.


“Complex behaviors may be encoded by a just a few genetic changes.” ~ American biologist Hopi Hoekstra