Not By Genes Alone

How Culture Functions as a Biological Trait

The American South has historically exhibited higher rates of violence than the North, a pattern that persists in modern homicide statistics. While some might attribute this to climate or economics, research suggests the cause is a culturally acquired "culture of honor." In this system, men believe their reputation is worth defending even at great cost. In laboratory settings, Southerners respond to insults with significant physiological spikes in stress and aggression hormones, whereas Northerners remain largely unaffected. This behavior is rooted in the history of the South, which was settled by livestock herders. In sparsely populated areas where livestock is easy to steal and the law is weak, a reputation for violent retaliation serves as a necessary deterrent. This cultural complex persists because it is passed from one generation to the next, demonstrating that culture is essential for understanding human behavior.

Culture is not a superorganic phenomenon existing outside of biology; rather, it is a fundamental part of human biology. It consists of information—ideas, values, and skills—acquired from others through teaching and imitation. This information is stored in human brains that have been shaped by millions of years of natural selection to learn and manage culture. Because culture is part of our biological makeup, it can trigger physical responses, such as the hormonal shifts seen in the culture of honor. To understand humans, one must use "population thinking," a concept borrowed from Charles Darwin. Just as biologists track how genetic variants spread or diminish in a population based on survival and reproduction, social scientists must track how cultural ideas spread or disappear based on how easy they are to learn, how attractive they are, or the social prestige of those who hold them.

A common mistake is to view human behavior as a choice between nature (genes) and nurture (environment). In reality, every behavior results from the interaction between genetic information and the environment. Natural selection does not just create fixed behaviors; it shapes the way an organism responds to its surroundings. Culture adds a unique layer to this interaction. For example, while humans have an innate aversion to bitter tastes to avoid toxins, we can culturally learn that a specific bitter plant has medicinal value. This culturally acquired belief allows a population to override its innate impulses. Thus, culture is a distinct system of inheritance that allows humans to adapt to new environments much faster than genetic evolution alone.

The human brain did not evolve to be a finished product that only then discovered culture. Instead, there was a constant feedback loop between our evolving psychology and the cultural information it was designed to process. During the rapid climate fluctuations of the last 800,000 years, the ability to imitate became a vital survival strategy. In unpredictable environments, relying on the collective wisdom of a group is often safer and more efficient than individual trial and error. This reliance on social learning led to a psychology that favors conformity and the imitation of successful individuals. While these traits allow for the rapid spread of useful technologies, they can also lead to the persistence of maladaptive fads or harmful traditions. Because culture is subject to its own selective pressures, it acts as an ultimate cause of behavior, much like genes. Ideas that promote the survival and expansion of a group—such as norms of cooperation and solidarity—tend to persist and spread.