In today’s ruthlessly competitive international economy, the United States may benefit from a potent but unheralded advantage: the aggressive edge sustained by the inherited power of American DNA.

The radical notion that our national character stems from genetics as well as culture has always inspired angry controversy; many observers scoff at the whole idea of a unifying hereditary component in our multi-racial, multi-cultural society. Aside from the varied immigrants who now make up nearly 15% of the population, the forebears of today’s Americans journeyed to this continent from Asia, Africa, Latin America and every nation of Europe. Our stark differences in appearance, if nothing else, argue against the concept of common DNA connecting contemporary citizens of wildly divergent ancestry. .

Nevertheless, two respected professors of psychiatry have recently come out with challenging books that contend that those who chose to settle this country in every generation possessed crucial common traits that they passed on to their descendents. In “American Mania,” Peter C. Whybrow of U.C.L.A. argues that even in grim epochs of starvation and persecution, only a small minority ever chooses to abandon its native land and to venture across forbidding oceans to pursue the elusive dream of a better life. The tiny percentage making that choice (perhaps only 2%, even in most periods of mass immigration) represents the very essence of a self-selecting group. Compared to the Irish or Germans or Italians or Chinese or Mexicans who remained behind in the “Old Country,” the newcomers to America would naturally display a propensity for risk-taking, for restlessness, for exuberance and self-confidence –traits readily passed down to subsequent generations. Whybrow explained to the New York Times Magazine that immigrants to the United States and their descendents seemed to possess a distinctive makeup of their “dopamine receptor system – the pathway in the brain that figures centrally in boldness and novelty seeking.”

John D. Gartner of Johns Hopkins University Medical School makes a similar case for an American-specific genotype in “The Hypomanic Edge”—celebrating the frenzied energy of American life that’s impressed every visitor since Tocqueville. The United States also benefited from our tradition of limited government, with only intermittent and ineffective efforts to suppress the competitive, entrepreneurial instincts of the populace. Professor Whybrow says: “Here you have the genes and the completely unrestricted marketplace. That’s what gives us our peculiar edge.” In other words, “anything goes capitalism” reflects and sustains the influence of immigrant genetics.

The idea of a distinctive, unifying, risk-taking American DNA might also help to explain our most persistent and painful racial divide – between the progeny of every immigrant nationality that chose to come here, and the one significant group that exercised no choice in making their journey to the U.S. Nothing in the horrific ordeal of African slaves, seized from their homes against their will, reflected a genetic predisposition to risk-taking, or any sort of self-selection based on personality traits. Among contemporary African-Americans, however, this very different historical background exerts a less decisive influence, because of vast waves of post-slavery black immigration. Some three million black immigrants from Africa and the Caribbean arrived since 1980 alone and in big cities like New York, Boston and Miami close to half of the African-American population consists of immigrants, their children or grandchildren. The entrepreneurial energy of these newcomer communities indicates that their members display the same adventurous instincts associated with American DNA.

If Whybrow, Gartner and other analysts are right about the role of inherited traits and tendencies in shaping our national character then the insight carries crucial political implications. Senators Obama, Clinton and other leaders who seek to enlarge the scope of government face more formidable obstacles than they realize. Their desire to impose a European-style welfare state and a command-and-control economy not only contradicts our proudest political and economic traditions, but the new revelations about American DNA suggest that such ill-starred schemes may go against our very nature.