If the Census Bureau has it right, the 300 millionth American entered the United States kicking and screaming this morning. The odds are that this milestone American is a boy, born to a white family in a California suburb. He will have a 1-in-4 shot of graduating from college, will probably marry, father two children, struggle with his weight, and live to see his 85th birthday.

What he will probably not have — that his grandfather likely did — is a pair of blue eyes.

Once a hallmark of the boy and girl next door, blue eyes have become increasingly rare among American children. Immigration patterns, intermarriage, and genetics all play a part in their steady decline. While the drop-off has been a century in the making, the plunge in the past few decades has taken place at a remarkable rate.

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.

Grant was moved to research the subject when he noticed that blue eyes were much more prevalent among his elderly patients in the nursing home where he worked than in the general population. At first he thought blue eyes might be connected to life expectancy, so he began comparing data from early 20th-century health surveys. Turns out it has more to do with marriage patterns.

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.

Elvis

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.

The influx of nonwhites into the United States, especially from Latin America and Asia, hastened the disappearance. Between 1900 and 1950, only about 1 in 10 Americans was nonwhite. Today that ratio is 1 in 3.

With the exception of an increased risk of macular degeneration (blue eyes are at greater risk) , eye color is biologically indicative of almost nothing. Boys are 3 percent to 5 percent likelier to have blue eyes than girls, but beyond that it’s a non-issue — physiologically speaking. The cultural implications are another story.

Preferences for fair skin and blue eyes stretch back in Europe to at least the Middle Ages, according to Hema Sundaram , author of “Face Value,” a book about the history of beauty. For women in particular, especially those of European descent, fair skin and light eyes have long been seen as indicators of fertility and beauty.

America adopted those biases early on, and Hollywood reinforced them by anointing a long line of blue-eyed blondes such as Marilyn Monroe as the nation’s sex symbols.

In the 1930s, eugenicists used the disappearance of blue eyes as a rallying cry to support immigration restrictions. They went so far as to map the parts of the country with the highest and lowest percentage of blue-eyed people.

So consumed were Americans with this ideal that in the ’70s and ’80s the fashion models who exemplified the All-American look were typically Scandinavian, said Katie Ford, CEO of Ford Models in New York, which has been in business for 60 years.

Robert Redford

But in the past decade those standards have begun to change, and Madison Avenue has taken note. The look advertisers want today favors honey-colored skin, brown hair, and green or brown eyes. The most successful models are coming from Brazil.

“Advertisers want the idealized form of the general population,” Ford said. “Someone with perfect features but who the everyday person can relate to.”

But even as blue eyes give way to brown, lighter eyes will maintain a certain allure, said Carolyn Kaufman, who teaches evolutionary psychology at Otterbein College in Ohio. When people see something pleasurable, their eyes dilate, Kaufman said. Dilated pupils signal happiness and are, in turn, considered attractive. Since they are easier to see on lighter eyes, they have a natural appeal.

Shopping at the North Shore Mall on Sunday, Carin Martinetti of Manchester held her 3-month-old daughter and studied her eyes hopefully. Martinetti, her husband, and their two other daughters all have brown eyes, but baby Alana’s eyes are light hazel. Whether they’ll stay that way remains to be seen.

“I hope so,” Martinetti said. “It would just make her unique.”

Many agree. Blue is by far the most popular color contact lens sold at 1-800-CONTACTS, the largest contact lens distributor in the country, said Tim Johnson, a spokesman for the company. But in the past four years something interesting has begun to happen. Blue is losing market share. Sales slipped from 53 percent to 45 percent, while brown jumped from 8 percent to 15 percent. Green, the second most popular color, held steady at 29 percent.

The best oil painting of AH ever, when he was not putting on the heroic pose — a sensitive, intelligent, often lonely, unarrogant, very nice guy, probably too nice

Close -up of his eyes as he peered out a plane window — classic German dark-blue

The Buddha was an Aryan prince from India, and famously had blue eyes, as statues all over Asia recall. Of course, he gave up his kingdom and the world for enlightenment, and so no way would such an enlightened man have kids. 😉

So is brown the new blue? Madison Avenue is paying attention, but most new parents have other things to worry about.

Not far from where the Martinettis were shopping, Stephen Kendig and his wife, Kellie, were strolling with their 3-month-old son, Ryan. They are waiting to see what color eyes he ends up with. So far they’re blue, like his mother’s. She hopes they stay that way.

Stephen is a bit more pragmatic.

“As long as they work,” he said.