Blue Eyes and Marriage Patterns

The Boston Globe reports:

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.

Harvard, the world's most elite dating agency, has most likely contributed to this trend.