She was just walking down the street with her sister, in her old neighborhood, when an elderly woman stopped her car in front of her and...

She was just walking down the street with her sister, in her old neighborhood, when an elderly woman stopped her car in front of her and called out, “I love your hair! It’s so beautiful!”

Caitlin Tydings was about 8 then, and caught off guard. Now a high-school senior, she has since grown accustomed to strangers commenting on her strawberry-blond locks.

If predictions by the Oxford Hair Foundation come to pass, the number of natural redheads everywhere will continue to dwindle until there are none left by the year 2100.

The reason, according to scientists at the independent institute in England, which studies all sorts of hair problems, is that just 4 percent of the world’s population carries the red-hair gene. The gene is recessive and therefore diluted when carriers produce children with people who have the dominant brown-hair gene.

Dr. John Gray’s explanation of his foundation’s findings: “The way things are going, red hair will either be extremely rare or extinct by the end of the century.”

Red hair certainly has made the endangered list. But with 4 percent of 6.4 billion people carrying the gene, says University of Rochester Medical Center’s David Pearce, it is too large a figure to be wiped out completely in the next 95 years.

“I think someone may want to check their calculator,” he says. The red-hair gene “will dilute out and become rare, but there are a variety of other factors that can change hair color that are not really understood well right now.”

The gene responsible for red hair was only discovered in the late 1990s. People have a good chance of being born with red hair if they have a mutation of that gene.

Red hair is found in all ethnic backgrounds but is most commonly associated with people of Celtic descent.

Red hair skipped two generations before sprouting on Brianna McBride, a 5-year-old preschooler from Penfield, N.Y. It comes from her great-grandmother on her father’s side.

“As a baby, we’d be in the store and people would always try to touch her head. She didn’t like that, so she was very shy,” recalls her mom, Alice. As Brianna got older, “we started to point out other redheads, and she started understanding.”

Now, her mom adds, “she looks forward to the attention. She has really learned how to use it.”