Black? White? Not so different Researchers have found that a small genetic variation of melanin, or pigment, helps determine skin color. Researchers locate gene linked to differing skin colors

The merest fragment of one gene plays a major role in the differing skin colors of white and black people, scientists have found, capping an 11-year effort that began with the study of similar color variations in a common pet-store critter, the zebra fish.

The team of 25 geneticists, molecular biologists and anthropologists, most of them from Pennsylvania State University, says the work could have implications for skin-cancer treatment, crime-scene analysis, and even cosmetics.

For those bent on altering their skin color, the gene could lead to pharmaceutical products that would be safer than tanning salons or the chemical skin-lightening creams popular in India, said project coordinator Keith C. Cheng, a cancer geneticist at the Penn State College of Medicine in Hershey.

The research, published today in the journal Science, also challenges a common assumption about when the various races branched off after leaving the scene of their common beginnings in Africa, more than 50,000 years ago. The people who would become Asians and northern Europeans were thought by some to have evolved their light skin together before migrating their separate ways.

The new research indicates that the two groups developed lighter skin after the separation - giving just a taste of the secrets of history that can be unlocked with the human genome, said Penn State anthropologist Mark Shriver.

"There's a lot left to be learned," Shriver said. "We're basically explorers right now."

Team members say the genetic variation they discovered accounts for about one-third of the difference in melanin, or pigment, between the skin of black and white people. Other skin-color genes had been found previously, but none plays such a significant role. Lighter skin may have evolved to help people absorb more light in climates with less sun so they can maintain vitamin D levels.

The underlying genetic code for the one-third variation seems, at a glance, to be almost inconsequentially small: a change in just one of the three billion base-pairs in the human genome.

So a significant part of the difference we perceive between the so-called races is caused by just one rung on the twisted ladder of our DNA. Otherwise, as geneticists have been discovering more and more as they study the human genome, we are all pretty much alike.

"There's more variation within [racial] populations than there is between," Cheng said.