The scientist and his companions puttered down winding waterways by boat, and bounced along dirt roads in a Ford Explorer. The longest of more than a dozen such trips into the Malaysian jungle took 10 hours.
Only then could the researcher from Penn State College of Medicine ask tribal leaders for the information he sought:
Surat warisan manusia. The letter of human inheritance.
That was Khai C. Ang's way of explaining the concept of DNA, and it was effective. Hundreds of villagers agreed to give blood samples, and now back in the Hershey, Pa., lab of Ang's supervisor, Keith Cheng, their DNA has begun to yield insight into a weighty trio of subjects: cancer, human migration, and race.
White people are prone to developing melanoma, as their pale skin is vulnerable to the sun's ultraviolet rays. Yet Asians, plenty of whom also have light skin, are relatively immune to the disease.
Cheng, director of experimental pathology at Penn State, thinks he can find out why. He chose to study DNA from the Malaysian jungle because its inhabitants have not intermingled with Europeans, for the most part, and because they have a range of skin colors -- like a living mosaic of evolution.
As a physician, Cheng fights cancer. But with genetic material like that at his disposal, he seems equally enthusiastic about anthropology, about the chance to describe a chapter of human history. "You'd have to be made of stone to not be curious how we got all these colors in humanity," Cheng said.
The story begins more than 50,000 years ago with Vitamin D. The body needs sunlight to make it, so when humans migrated out of Africa, they likely became vitamin-deficient. Blame the weaker northern sunlight, and the fact that in the colder climate, they had to cover more of their skin with clothing.
But people with lighter skin can more readily make Vitamin D. So those with that trait would have been healthier, likely explaining why they came to dominate the northern latitudes. One light-skinned group spread across Europe, the other across Asia.
Yet the mutations that gave rise to European skin were accompanied by about a 20-fold rise in melanoma. The skin of Asians, on the other hand, is somehow nearly as good as dark African skin at absorbing harmful ultraviolet radiation, keeping it away from the nucleus of skin cells.
On the advice of Oxford University scholar Stephen Oppenheimer, whose book The Real Eve describes human migration from Africa, Cheng sought answers in peninsular Malaysia. The region is home to three tribal groups that have been largely insulated from European influence: the Senoi, the Proto-Malay, and the Negrito.
At the national university near Kuala Lumpur, Cheng met Ang and quickly sold him on his idea to gather DNA in the jungle.
He explained how, once they had the genetic samples back at Penn State, they would test various genes by tamping them down in zebrafish, a popular creature in pet stores but also increasingly a valued lab tool. If a gene contributed to lighter skin color in humans, fish with that gene should follow suit.
But first, the team needed to get permission: from various Malaysian agencies, from the national university, from Penn State, and above all from the villagers. Among the concerns was that the tribe members grasp the goal of the research so they could give informed consent.
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