Avi Tuschman may be on to something — or he bit off more than he can chew. The Stanford University anthropology PhD's soft-spoken manners juxtapose with the strident character of his first book, "Our Political Nature." The title's ambition, rest assured, is commensurate with the expansive reach of the book's thesis.

However, the breadth (and length) of the work provides ample opportunities for both enjoyment and disgorgement. Tuschman is a 34-year-old Menlo Park resident who since graduating from Stanford has served as the senior writer and advisor to former Peruvian President Alejandro Toledo. He also worked with a couple of multi-lateral development banks to mediate social and economic conflicts in developing countries.

"'Our Political Nature' is the first science book on human political orientation. It's the first book to tell the natural history of the left-right spectrums that define politics around the world," Tuschman said in an interview.

To be sure, he is not the first person to study the science of politics. But what makes his book original, and so boggling, is that it tries to link mountains of studies from fields as diverse as anthropology, evolutionary biology, psychology, political science, economics and others in an attempt to demonstrate his startling central claim: People's political orientations across space and time are a product of three clusters of measurable personality traits — tribalism, attitude towards inequality and perceptions of human nature — that are in turn a product of evolutionary biology.

His conclusion has panache, too.

"Anywhere between 40 to 60 percent of the variance in our political orientations comes from genetic differences between individuals. To be clear, that's a measurement of the proportion of variance in a population between individuals. It doesn't mean that half of your views are genetically inherited. Nonetheless, a substantial part of our political orientation has a genetic component," he said.

The book is the product of a 10-year process that began in 2002 after Tuschman finished his undergraduate career at Stanford. "I saw first-hand in Peru the consequences of extreme political polarization. People were living and dying because of these radically different world views. I wrote reflections on what I observed, and I went back to Stanford and started studying different explanations for how people end up with such different political orientations," he said.

As Tuschman describes it, his thesis flies in the face of the social-science consensus, which stipulates that people's political views are mostly a product of parents, teachers, culture and the environment. Tuschman does not deny that these factors play a large role, but he is convinced genetics do, too.

"We've known for decades that there is a substantial heritable component of political orientation. It was ignored because it goes against everything we've understood about the social sciences. I discovered that our constitutions could load the dice and make us more likely to lean to the left or the right. It became very clear that something very deep and biological is going on and that it needed explaining." Therein lies the rub.

The tribalism cluster breaks down to ethnocentricity, religiosity and sexual (in)tolerance. All three are interrelated but distinguishable. People who have ethnocentric (xenophobic), religious and sexually intolerant traits tend to be on the right side of the spectrum, and those with opposite traits (xenophilic, secular and sexually liberal) are typically on the left. Tuschman argues that these traits have deep evolutionary roots based on our earliest primogenitors' decisions to inbreed (reproduce within a related group) or outbreed (reproduce with members of out-groups). Millions of years of these different types of reproductive decisions have naturally selected for genes that code for either tribalistic or non-tribalistic personality traits.

The second major cluster, attitude towards inequality, also corresponds with the left-right spectrum. Those who are tolerant of inequality and favor hierarchical structures tend to be on the right while those who are more intolerant of inequality and favor egalitarian structures tend to go left. Tuschman argues these attitudes originate in conflicts within our ancestors' nuclear families. Through an evolutionary lens, parents and their offspring and siblings are locked in constant struggle; children, in their fight to survive, demand more resources from their parents than they are willing to provide and siblings compete for their parents' resources. This constant struggle over the course of millions of years led to the natural selection of certain genes that predispose us towards favoring either hierarchy or egalitarianism.

Finally, the third major cluster is perceptions of human nature. Like tribalism and tolerance of inequality, Tuschman claims perceptions of human nature are also on a spectrum with "cooperative" on the left and "competitive and self-interested" on the right. Tuschman writes that the "modern fields (of science) have objectively defined and measured altruism and self-interest" and that "it's time for political science to approach human nature from a scientific perspective." He claims the conservatives and liberals abide by different types of altruism — reciprocal for liberals and kin-selection for conservatives — that are linked to different hormones and receptors in the brain that are products of evolution.

So what are we to make of all this information? Tuschman bookends his thesis with pleas for people to understand the roots of political polarization. Liberals and conservatives are literally different people and, if we are to believe Tuschman, ineradicably so. Yet, he calls for people to "transcend the attitudes that still divide us" and for political moderation to triumph.

As with any tome that makes large claims, there is substantial room for heavy criticism. The logical connections between personality traits and evolved genes remain tenuous, partly because scientists have not deciphered the many functions of our genomic 'dark matter,' the vast stretches of non-coding DNA that comprise 98 percent of our genome; doing so will likely account for the missing heritability of many known traits. Nonetheless, Tuschman is optimistic that this will be accomplished in our lifetimes and that these connections will be unequivocally established.

Additionally, Tuschman's attempt to "illuminate our true human nature" is very problematic. After sprinting through 2,000 years of philosophical thought in seven pages, he unceremoniously shoves the entire discipline out of the conversation. He argues that dismissal is warranted because philosophers' "state of nature" thought experiment does not match up with actual anthropological history. With total disregard for irony, he writes that philosophy only views human nature "as basically 'good' or 'bad'" and is not complex and nuanced enough to be of value — and proceeds to cram human nature into a "scientific" spectrum.

None of that is to say Tuschman's effort was misguided or a waste. Indeed, he saturates the reader with enough reasons to support further inquiry and to wonder just how much our genetics "load our political dice." Some of the information he presents is delightfully unsettling. However, this first attempt at unifying a relatively new field brings to mind the converse of Aristotle's famous phrase. In this case, the sum of the parts is greater than the whole.

PULL QUOTE:

'Our constitutions could load the dice and make us more likely to lean to the left or the right.'

— Avi Tuschman, author, "Our Political Nature"