(NEW YORK) -- The blond gods and goddesses worshiped by ancient Greeks and Romans may have owed their glamorous locks to an extraordinarily complex but incredibly tiny change in the part of the genome that determined what they looked like.
And all these years later, that same mutation is still at work, grinding out humans with golden hair, some of whom are worshiped today.
New research showing how one small change in DNA -- the master plan for each organism -- altered the course of human history by introducing blonds to the world thousands of years ago also adds a little credibility to the notion that gentlemen really do prefer blondes.
"Blond is a color that has been alluring for a long time in European culture," where the first blonds appeared as early humans worked their way north, David Kingsley, professor of development biology at Stanford University and senior author of a study published in the journal Nature Genetics, said in a telephone interview.
Kingsley really isn't all that interested in why blondes are held in such high esteem, or even why a small percentage of humans have blond hair. He wants to know how that change came about.
For the past few years scientists have been intrigued by the traits that make me different from you, and they are making significant progress in figuring out how different genes do different things.
It seemed so much simpler just a couple of decades ago. It was widely believed that genes were turned on, or off, (called expressed) so if you wanted to cure cancer, all you had to do was figure out which gene to shut down, or crank up, depending on whether that gene caused or cured cancer.
But the human genome project shattered that simple myth.
Kingsley's study vividly demonstrates that a single gene can do many things, and it doesn't have to be turned on or off. It can be "dialed up, or down," said Kingsley, who is also a scientific investigator for the Howard Hughes Medical Institute.
To create a line of brown mice with blondish hair, the scientists just had to tweak the expression of a single gene by about 20 percent. That same gene is responsible for many other functions throughout the mouse genome, and it continued on with its other duties, unaffected by that small change.
That is the same process that has been passed from one human generation to the next since the first blonds appeared.
Kingsley said scientists now think only a very small percent of DNA actually does what they used to think was the only function of genes, producing proteins to build everything from heart muscles to skin cells. Instead, he said, most of the DNA is part of the genome's internal regulatory system, turning some genes on or off, or dialing them up or down.
That's why a single gene -- like the one that produces blond hair -- can do many things in many places.
"I like the analogy of zone controlled heat," he said. "You have a furnace in the house, you've got thermostats in different rooms and you can dial up or down the heat and adjust the temperature in a single room."
If the furnace stops working, every room gets cold. But if a thermostat in one room is changed, only that room is affected. And that's what occurred in his mice.
Adjusting the "thermostat" by just 20 percent produced a change in hair color, but other functions attributed to that same gene elsewhere in the body continued uninterrupted.
This gene is not the only one involved in producing blond hair color. There are about six other genes involved, but it's significant that tweaking this gene, and only this gene, produced such a dramatic result.
Again, these scientists aren't trying to figure out how to produce more blonds. That ambition died out with Nazi Germany. What they want to do is determine which of the millions of genes needs to be tweaked, and how much, to help the body fight a specific illness, or respond to a certain drug, without messing up the entire system.
That's a huge challenge, but this research, like others, suggests it's possible.
But does it really say anything about an evolutionary preference for blonds?
Evolution is based on natural selection -- an organism selects a mutation because it is useful -- like a cave man who can whip every guy in the clan. He's so admired that he mates often, passing on his muscle genes to many offspring, who eventually become dominant.
However, Charles Darwin and many biologists since have argued over something called "sexual selection." Do we select some mutations because they make us sexy?
Birds do, obviously. Bright plumage attracts mates, so the birds with fancy feathers produce more offspring.
That would suggest sexual selection is why so many women become blondes, either with or without chemical aids.
But not necessarily, according to Kingsley. The same gene that produces blond hair also is involved in lighter skin pigment. As early humans moved north out of Africa, they encountered a much less sunny climate and no longer needed the dark skin that protected them from ultraviolet radiation from the sun, so they "selected" for lighter skin, which helped them absorb more vitamin D.
That clearly is a survival advantage. But blond hair?
Maybe we like blonds just because they are different. Humans started out with dark hair, dark skin and dark eyes. The first blonds appeared in northern Europe and Scandinavia, and have since turned up in other areas, including the Solomon Islands northeast of Australia, known for the darkest skin outside of Africa.
The appearance of blond natives in the Solomon Islands was due to a gene mutation that was completely different from the change that introduced blondness to Europe, and it had an unpleasant effect. The first natives on those islands who showed up with blond hair were treated as freaks.
By the way, not all blonds were gods and goddesses among the ancient Greeks and Romans. Prostitutes also colored their hair blond.
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