Taxes, healthcare, national security. These are the issues that most people would say differentiate one political party from another, one candidate from another. But in fact, these issues are only symptomatic of what actually differentiates candidates: sex.

The 2016 presidential elections in the United States—Hillary Clinton vs. Donald Trump—exemplified how gender manifests in political conflict, from defining their personality types to shaping their entire ideological worldview. And the heated nature of that contest showcased the split across gender lines, exhibiting how sexual relations is threatening to tear Western society apart. We are heading for a “cultural divorce.”

The masculine versus feminine

The strong, masculine personality type projected by Donald Trump stands for an “America First” vision for the world: a more self-interested policy in which the interests of the American people are preferred, with closed borders that protect national interests and promote national identity and culture. This is contrasted with Hillary’s globalist, more inclusive vision for humanity that promotes altruistic sacrifice of self-interest, driven by the feminine characteristic of empathy and social bonding in order to unify a multicultural global community by eliminating the old order.

By studying our political strife from a social-science perspective we can better understand the inherent forces that drive social conflict. Social bonding is an incredibly important quality that enables the rise of complex human societies with shared intentionality, the cultural transmission of knowledge, and the division of labor. The feminine attributes of empathy and love are significant in connecting people into social networks that allow for mutual cooperation and exchange of ideas and trade.

A completely anti-social personality could not interact with others. However, if our social bonds become too tight, those social connections can flip from bonded to bondage, restricting the degree of freedom needed to develop individual character and take personal responsibility for our actions. Social bondage prohibits creativity, rationality, and objectivity. Hence we need to balance the feminine side of social bonding and altruism with the masculine side of rational self-interest and a greater degree of independence.

In view of how this distinction between the genders shapes our political divide, we can gain valuable insights from recent studies in neuroscience on how hormones drive our sexual differentiation and structure our brain. It is important to understand that we all begin as females in the womb, but the rise of the sex hormone, testosterone, leads to the development of male characteristics in utero. Again in puberty, the growth of sex hormones kick in to further induce development of the different genders.

The driver of civilization

In humans, as in most mammal species, it is the males that compete for social status to gain access to the females. Females act as Mother Nature’s selectors, choosing their preferred mate and thereby which men will succeed in propagating their genes into future generations.

The dominant, alpha male personality type and culture, in the context of competition between greater social groups, such as nations, secures territory and resources in order to protect and provide for their females and build a nest. The biological imperative to reproduce and procure the resources to raise our children is the underlying theme in shaping our human history and social and political traditions. These are the biological origins for the modern concept of the Western nation state with secure borders. The rule of law and order is established to promote the rise of a flourishing and civilized society.

However, if we study human history, much of it is shaped by periods of imperialist wars of aggression in which the lack of respect for definite boundaries between social groups leads to increased violence and conflict. The strong conquer the weak, uniting many cultures under great empires.

Examples of these are the Roman Empire, the Islamic Empire, or the empire created by the Mongol hoards that conquered a huge land mass across Eurasia, from China to the Middle East and Russia. In the twentieth century, both the fascist regimes of Nazi Germany and the Communists in Soviet Russia sought to conquer huge empires under their control. History teaches us that lack of secured borders leads to wars of aggression in which men fight over resources and females, leading to conquest and rape.

The modern concept of the nation state has only emerged since the Age of Enlightenment in the seventeenth century, in which European societies decided to promote peaceful coexistence by defining national borders and securing the rule of law. The cultures that developed, like the United States, promoted individual rights, and men were able to compete economically to enhance production by more efficiently utilizing natural resources, rather than battling to control and enslave each other.

In my recent book, The Testosterone Hypothesis, I make the case that it is actually the rise of the male hormone testosterone that has led to modern Western civilization in which national and personal independence and liberty are the celebrated values of free men. This masculine culture, in which men feel secure and confident under the rule of law, promotes independence and challenges centralized authority as the Founding Fathers of the United States did in their rebellious war for Independence in 1776, fighting for these Enlightenment ideals.

However as testosterone declines, men lose their drive for self-determination and their internal locus of control and become increasingly dependent and subjugated by socialist state controls and centralized forms of government that become more imperial and all encompassing, encroaching on the sovereignty of the individual.

This hormonal view of history is confirmed by recent scientific studies on the effects of testosterone on men’s political ideology. A study done in 2013 by Danish scientists found that stronger men correlate with more conservative  political and economic views. The study was conducted among hundreds of men in the U.S., Denmark, and Argentina, and the researchers concluded that men’s relative physical strength is indicative of their ability to defend their families and procure resources to provide for them:

This is among the first studies to show that political views may be rational in another sense, in that they’re designed by natural selection to function in the conditions recurrent over human evolutionary history.

Our sex hormones determine the degree of independence versus bonding that takes place in how we organize our social structure. Hence, we need to further study and integrate the natural sciences—primarily biology and neuroscience—with the humanities to reach a more comprehensive level of understanding of our mind-body connection and how evolved sexual reproductive strategies drive the organization of our society, culture, and political ideologies accordingly.