Blue Eyes and Marriage Patterns
Harvard, the world's most elite dating agency, has most likely contributed to this trend.
About half of Americans born at the turn of the 20th century had blue eyes, according to a 2002 Loyola University study in Chicago. By mid-century that number had dropped to a third. Today only about one 1 of every 6 Americans has blue eyes, said Mark Grant, the epidemiologist who conducted the study....
A century ago, 80 percent of people married within their ethnic group, Grant said. Blue eyes -- a genetically recessive trait -- were routinely passed down, especially among people of English, Irish, and Northern European ancestry.
By mid-century, a person's level of education -- and not ethnicity -- became the primary factor in selecting a spouse. As intermarriage between ethnic groups became the norm, blue eyes began to disappear, replaced by brown.