This story is a supplement to the feature "The Migration History of Humans: DNA Study Traces Human Origins Across the Continents" which was printed in the July 2008 issue of Scientific American.

In their quest for a more in-depth picture of human origins, geneticists need more samples from indigenous populations the world over. “There’s a need for greater resolution in the data,” says Marcus W. Feldman of Stanford University and a co-author of a recent whole-genome comparative analysis. “If you were to give me $1 million tomorrow, I’d find 100 more populations out of the 5,000 we need.”

An equal hurdle may be overcoming objections to this kind of research. In 1991 Luigi Luca Cavalli-Sforza and his colleagues outlined a vision for the Human Genome Diversity Project, which would have created a store of cells from 25 unrelated individuals from each of some 400 populations worldwide. The project foundered, however, because of resistance from indigenous groups to providing samples: one group called it a “Vampire Project.” Despite extensive informed consent procedures, some groups worried about whether the samples would be used in research for patenting and developing new drugs, which  they considered to be a form of biopiracy.

The project never received more than planning support from the federal government, but a more modest version began in this decade, based on cell lines that various population geneticists had brought together on their own from more than 1,000 individuals. This collection, known as the Human Genome Diversity Panel, is stored at the Center for the Study of Human Polymorphisms in Paris. So far it has provided a database containing information on 51 populations that has been used for various studies, including two large, transgenomic investigations reported in Nature and Science this past February.

Like the Human Genome Diversity Project, the more recent Genographic Project, which intends to gather DNA from 100,000 indigenous people, is also facing opposition. The project has careful protocols for ensuring informed consent in sample gathering, and it does not intend to make collections for medical research. Yet it has still run into resistance, in particular, from Native American groups.

No matter what assurances are given, some groups will be reluctant to yield a cheek swab or blood sample. Investigators in this field may never achieve their goal of obtaining a set of samples that fully reflects every subtle gradation of human genetic diversity.