Whybrow, himself a British immigrant, advances the anthroposocial hypothesis that we Americans are a nation of "migrants" who are equipped not just with the selfish genes of all biology but also with the restless, adventuresome genes of those who have risked all to seek a new land of opportunity. The book’s argument relies on the work of Chuansheng Chen and his co-workers (1), who correlated a greater percentage of certain dopamine-4 alleles, specifically 7-repeats and long alleles (5- to 11-repeats), with exploratory human nature—novelty-seeking personality, hyperactivity, and risk-taking—in human groups who have "macro-migrated." The 4-repeats, according to this argument, are more prevalent in sedentary groups. It is the opinion of Chen (whose name is misspelled) and his co-workers that the gene variation is the natural selective result rather than the cause of migratory culture over thousands of years and that recent U.S. immigrants (Japanese, Chinese, and Europeans) do not show the effect. The effect is seen, for example, in Colombian Indians who migrated far across the Bering land bridge 10,000 and 5,000 years ago. Granted, North American Native Americans, who are rich in 7-repeats, have contributed to the casino bubble, but this is not necessarily a sign of risk-taking, because this business has not proved very risky for them and, in any case, they have had help from other Americans of European ancestry. The savings and loan and Internet collapses, caused by risk-taking, were associated with Americans of European ancestry, who have the same number of repeats and alleles as their forebears.