Twin boys born in Germany July 11 are turning heads for more than their baby faces: in an unusual genetic occurrence, the brothers were born with dramatically different skin colors.
The babies' mother, Florence Addo-Gerth, called her twin infants "black and white" in an interview with German broadcaster RTL.
The older twin, Ryan, takes after his white German father, Stephan Gerth, while the younger, Leo, looks more like Addo-Gerth, who hails from Ghana in West Africa, she said.
"I could not believe it at first, I think people will probably laugh when they see my boys and hear they are twins," Addo-Gerth told RTL.
But while some passersby will stop and stare, others might not even blink an eye -- and with good reason, according to genetics experts.
"That sort of combination is not as rare as you might think," says Dr. Melissa Fries, director of genetics and fetal medicine at Washington Hospital Center in Washington, D.C.
She says she was "not a bit" shocked by the recent news, and cites the handful of similar cases to occur in the past three year, including several sets of twins born in the U.K. to mixed-race couples.
In fact, dramatically different twins are born every day. This occurrence is no different than if one twin was a curly-haired brunette and the other a straight-haired redhead, says Lawrence Balter, professor of applied psychology at New York University.
"Fraternal twins are just two children born at the same time," he says.
Birthing twins who have different skin colors might seem like a one-in-a-million shot, but the odds are dictated by genetics.
"Just as siblings receive different genes, so do fraternal twins," Fries says.
Fraternal twins are the product of two different eggs fertilized by two different sperm. Therefore, they receive different genetic information.
Scientists believe that at least seven genes are responsible for a person's external hue, Fries says. And though it's more likely that the genes from the mother and father would have caused both children to have blended skin tones, it's simply a matter of chance that the children ended up as opposites.
"That is how our genes work," Fries says. "They randomly assort. ... If you look at human beings, we are all slightly different colors."
Though these twins have likely drawn attention from day one, experts say that the German brothers need a few more years to understand their chromosomal coincidence.
"No child could possibly understand what's going on here until they were probably elementary-school aged," says Ricardo Ainslie, a psychoanalyst and professor of educational psychology at the University of Texas-Austin. "It's a very abstract and complicated thing to make sense of."
While the children may not understand the genetic basis for the difference, it may cause them to identify more with the parent with whom their skin color is closest -- similar to a set of opposite-sex twins in which the male identifies with the father and the female with the mother, Ainslie says.
To children, it's simple, says Washington Hospital's Fries: "I got my color from mommy and you got your color from daddy."
The difference might only become an issue when the children reach school age.
"Until the world becomes defined in racial terms ... they may not fully grasp it," Ainslie says of the skin color difference. "It may just feel like part of the known world."